process load balancing: broken but in progress

2026-08-08 00:22:14 +01:00 · 2019-09-19 17:28:29 +02:00
parent c5429f7efa
commit 171f93662f
33 changed files with 1681 additions and 117 deletions
--- a/2
+++ b/2
@@ -52,7 +52,7 @@ image:

 # start the API using previously built Docker image.
 gotenberg:
-	docker run -it --rm -e MAXIMUM_WAIT_TIMEOUT=$(MAXIMUM_WAIT_TIMEOUT) -e MAXIMUM_WAIT_DELAY=$(MAXIMUM_WAIT_DELAY) -e MAXIMUM_WEBHOOK_URL_TIMEOUT=$(MAXIMUM_WEBHOOK_URL_TIMEOUT) -e DEFAULT_WEBHOOK_URL_TIMEOUT=$(DEFAULT_WEBHOOK_URL_TIMEOUT) -e MAXIMUM_WEBHOOK_URL_TIMEOUT=$(MAXIMUM_WEBHOOK_URL_TIMEOUT) -e DEFAULT_LISTEN_PORT=$(DEFAULT_LISTEN_PORT) -e DISABLE_GOOGLE_CHROME=$(DISABLE_GOOGLE_CHROME) -e DISABLE_UNOCONV=$(DISABLE_UNOCONV) -e LOG_LEVEL=$(LOG_LEVEL)  -p "3000:$(DEFAULT_LISTEN_PORT)" $(DOCKER_REPOSITORY)/gotenberg:$(VERSION)
+	docker run -it --rm -e MAXIMUM_WAIT_TIMEOUT=$(MAXIMUM_WAIT_TIMEOUT) -e MAXIMUM_WAIT_DELAY=$(MAXIMUM_WAIT_DELAY) -e MAXIMUM_WEBHOOK_URL_TIMEOUT=$(MAXIMUM_WEBHOOK_URL_TIMEOUT) -e DEFAULT_WEBHOOK_URL_TIMEOUT=$(DEFAULT_WEBHOOK_URL_TIMEOUT) -e MAXIMUM_WEBHOOK_URL_TIMEOUT=$(MAXIMUM_WEBHOOK_URL_TIMEOUT) -e DEFAULT_LISTEN_PORT=$(DEFAULT_LISTEN_PORT) -e DISABLE_GOOGLE_CHROME=$(DISABLE_GOOGLE_CHROME) -e DISABLE_UNOCONV=$(DISABLE_UNOCONV) -e LOG_LEVEL=$(LOG_LEVEL)  -p "$(DEFAULT_LISTEN_PORT):$(DEFAULT_LISTEN_PORT)" $(DOCKER_REPOSITORY)/gotenberg:$(VERSION)

 # publish Gotenberg images according to version.
 publish:
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ At TheCodingMachine, we build a lot of web applications (intranets, extranets an

 * HTML and Markdown conversions using Google Chrome headless
 * Office conversions (.txt, .rtf, .docx, .doc, .odt, .pptx, .ppt, .odp and so on) using [unoconv](https://github.com/dagwieers/unoconv)
-* Performance :zap:: Google Chrome and LibreOffice (unoconv) started once in the background thanks to PM2
+* Performance :zap:: Google Chrome and LibreOffice started once in the background thanks to PM2
 * Failure prevention :broken_heart:: PM2 automatically restarts previous processes if they fail
 * Assets :package:: send your header, footer, images, fonts, stylesheets and so on for converting your HTML and Markdown to beaufitul PDFs!
 * Easily interact with the API using our [Go](https://github.com/thecodingmachine/gotenberg-go-client) and [PHP](https://github.com/thecodingmachine/gotenberg-php-client) libraries
--- a/build/docs/content/00-introduction.md
+++ b/build/docs/content/00-introduction.md
@@ -6,7 +6,7 @@ title: Introduction

 * HTML and Markdown conversions using Google Chrome headless
 * Office conversions (.txt, .rtf, .docx, .doc, .odt, .pptx, .ppt, .odp and so on) using [unoconv](https://github.com/dagwieers/unoconv)
-* Performance: Google Chrome and LibreOffice (unoconv) started once in the background thanks to PM2
+* Performance: Google Chrome and LibreOffice started once in the background thanks to PM2
 * Failure prevention: PM2 automatically restarts previous processes if they fail
 * Assets: send your header, footer, images, fonts, stylesheets and so on for converting your HTML and Markdown to beaufitul PDFs!
 * Easily interact with the API using our [Go](https://github.com/thecodingmachine/gotenberg-go-client) and [PHP](https://github.com/thecodingmachine/gotenberg-php-client) libraries
--- a/cmd/gotenberg/main.go
+++ b/cmd/gotenberg/main.go
@@ -8,7 +8,8 @@ import (

 	"github.com/thecodingmachine/gotenberg/internal/app/xhttp"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
-	"github.com/thecodingmachine/gotenberg/internal/pkg/pm2"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/prinery"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/process"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xcontext"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
 )
@@ -26,22 +27,30 @@ func main() {
 	}
 	systemLogger.InfofOp(op, "Gotenberg %s", version)
 	systemLogger.DebugfOp(op, "configuration: %+v", config)
-	// start PM2 processes.
-	var processes []pm2.Process
-	if !config.DisableGoogleChrome() {
-		processes = append(processes, pm2.NewChromeProcess(systemLogger))
+	// create PM2 manager and start processes.
+	manager := process.NewPM2Manager(systemLogger, config)
+	if err := manager.Start(); err != nil {
+		systemLogger.FatalOp(op, err)
 	}
-	/*if !config.DisableUnoconv() {
-		processes = append(processes, pm2.NewUnoconvProcess(systemLogger))
-	}*/
-	for _, p := range processes {
-		systemLogger.InfofOp(op, "starting '%s' with PM2...", p.Fullname())
-		if err := p.Start(); err != nil {
+	// create prineries.
+	var chromePrinery *prinery.Prinery
+	if !config.DisableGoogleChrome() {
+		chromePrinery, err = prinery.New(systemLogger, manager, process.ChromeKey)
+		if err != nil {
 			systemLogger.FatalOp(op, err)
 		}
+		go chromePrinery.Start()
+	}
+	var sofficePrinery *prinery.Prinery
+	if !config.DisableUnoconv() {
+		sofficePrinery, err = prinery.New(systemLogger, manager, process.SofficeKey)
+		if err != nil {
+			systemLogger.FatalOp(op, err)
+		}
+		go sofficePrinery.Start()
 	}
 	// create our API.
-	srv := xhttp.New(config, processes...)
+	srv := xhttp.New(config, manager, chromePrinery, sofficePrinery)
 	// run our API in a goroutine so that it doesn't block.
 	go func() {
 		systemLogger.InfofOp(op, "http server started on port '%d'", config.DefaultListenPort())
@@ -66,13 +75,6 @@ func main() {
 	if err := srv.Shutdown(ctx); err != nil {
 		systemLogger.FatalOp(op, err)
 	}
-	// shutdown PM2 processes.
-	for _, p := range processes {
-		systemLogger.InfofOp(op, "shutting down '%s' with PM2...", p.Fullname())
-		if err := p.Stop(); err != nil {
-			systemLogger.FatalOp(op, err)
-		}
-	}
 	systemLogger.InfoOp(op, "bye!")
 	os.Exit(0)
 }
--- a/internal/app/xhttp/handler.go
+++ b/internal/app/xhttp/handler.go
@@ -9,7 +9,9 @@ import (
 	"github.com/thecodingmachine/gotenberg/internal/app/xhttp/pkg/context"
 	"github.com/thecodingmachine/gotenberg/internal/app/xhttp/pkg/resource"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/pm2"
-	"github.com/thecodingmachine/gotenberg/internal/pkg/printer"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/prinery"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/print"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xcontext"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xrand"
@@ -39,6 +41,7 @@ func pingHandler(c echo.Context) error {
 		if logger.Level() != xlog.DebugLevel {
 			return nil
 		}
+		// TODO
 		list, err := pm2.List()
 		if err != nil {
 			return err
@@ -59,17 +62,18 @@ func mergeHandler(c echo.Context) error {
 		ctx := context.MustCastFromEchoContext(c)
 		logger := ctx.XLogger()
 		logger.DebugOp(op, "handling merge request...")
+		config := ctx.Config()
 		r := ctx.MustResource()
-		opts, err := mergePrinterOptions(r, ctx.Config())
+		timeout, err := resource.WaitTimeoutAndWaitDelayArg(r, config)
 		if err != nil {
-			return xerror.New(op, err)
+			return err
 		}
 		fpaths, err := r.Fpaths(".pdf")
 		if err != nil {
 			return err
 		}
-		p := printer.NewMergePrinter(logger, fpaths, opts)
-		return convert(ctx, p)
+		p := print.NewMergePrint(logger, fpaths)
+		return convert(ctx, nil, p, timeout)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -83,10 +87,16 @@ func htmlHandler(c echo.Context) error {
 	const op string = "xhttp.htmlHandler"
 	resolver := func() error {
 		ctx := context.MustCastFromEchoContext(c)
+		prinry := ctx.MustChromePrinery()
 		logger := ctx.XLogger()
 		logger.DebugOp(op, "handling HTML request...")
+		config := ctx.Config()
 		r := ctx.MustResource()
-		opts, err := chromePrinterOptions(r, ctx.Config())
+		timeout, err := resource.WaitTimeoutAndWaitDelayArg(r, config)
+		if err != nil {
+			return err
+		}
+		opts, err := chromePrintOptions(r, config)
 		if err != nil {
 			return err
 		}
@@ -94,8 +104,8 @@ func htmlHandler(c echo.Context) error {
 		if err != nil {
 			return err
 		}
-		p := printer.NewHTMLPrinter(logger, fpath, opts)
-		return convert(ctx, p)
+		p := print.NewHTMLPrint(logger, fpath, opts)
+		return convert(ctx, prinry, p, timeout)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -109,10 +119,16 @@ func urlHandler(c echo.Context) error {
 	const op string = "xhttp.urlHandler"
 	resolver := func() error {
 		ctx := context.MustCastFromEchoContext(c)
+		prinry := ctx.MustChromePrinery()
 		logger := ctx.XLogger()
 		logger.DebugOp(op, "handling URL request...")
+		config := ctx.Config()
 		r := ctx.MustResource()
-		opts, err := chromePrinterOptions(r, ctx.Config())
+		timeout, err := resource.WaitTimeoutAndWaitDelayArg(r, config)
+		if err != nil {
+			return err
+		}
+		opts, err := chromePrintOptions(r, config)
 		if err != nil {
 			return err
 		}
@@ -127,8 +143,8 @@ func urlHandler(c echo.Context) error {
 		if err != nil {
 			return err
 		}
-		p := printer.NewURLPrinter(logger, remoteURL, opts)
-		return convert(ctx, p)
+		p := print.NewURLPrint(logger, remoteURL, opts)
+		return convert(ctx, prinry, p, timeout)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -142,10 +158,16 @@ func markdownHandler(c echo.Context) error {
 	const op string = "xhttp.markdownHandler"
 	resolver := func() error {
 		ctx := context.MustCastFromEchoContext(c)
+		prinry := ctx.MustChromePrinery()
 		logger := ctx.XLogger()
 		logger.DebugOp(op, "handling Markdown request...")
+		config := ctx.Config()
 		r := ctx.MustResource()
-		opts, err := chromePrinterOptions(r, ctx.Config())
+		timeout, err := resource.WaitTimeoutAndWaitDelayArg(r, config)
+		if err != nil {
+			return err
+		}
+		opts, err := chromePrintOptions(r, config)
 		if err != nil {
 			return err
 		}
@@ -153,11 +175,11 @@ func markdownHandler(c echo.Context) error {
 		if err != nil {
 			return err
 		}
-		p, err := printer.NewMarkdownPrinter(logger, fpath, opts)
+		p, err := print.NewMarkdownPrint(logger, fpath, opts)
 		if err != nil {
 			return err
 		}
-		return convert(ctx, p)
+		return convert(ctx, prinry, p, timeout)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -171,10 +193,16 @@ func officeHandler(c echo.Context) error {
 	const op string = "xhttp.officeHandler"
 	resolver := func() error {
 		ctx := context.MustCastFromEchoContext(c)
+		prinry := ctx.MustSofficePrinery()
 		logger := ctx.XLogger()
 		logger.DebugOp(op, "handling Office request...")
+		config := ctx.Config()
 		r := ctx.MustResource()
-		opts, err := officePrinterOptions(r, ctx.Config())
+		timeout, err := resource.WaitTimeoutAndWaitDelayArg(r, config)
+		if err != nil {
+			return err
+		}
+		opts, err := officePrintOptions(r, config)
 		if err != nil {
 			return err
 		}
@@ -195,8 +223,8 @@ func officeHandler(c echo.Context) error {
 		if err != nil {
 			return err
 		}
-		p := printer.NewOfficePrinter(logger, fpaths, opts)
-		return convert(ctx, p)
+		p := print.NewOfficePrint(logger, fpaths, opts)
+		return convert(ctx, prinry, p, timeout)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -204,7 +232,7 @@ func officeHandler(c echo.Context) error {
 	return nil
 }

-func convert(ctx context.Context, p printer.Printer) error {
+func convert(ctx context.Context, prinry *prinery.Prinery, prnt print.Print, timeout float64) error {
 	const op string = "xhttp.convert"
 	resolver := func() error {
 		logger := ctx.XLogger()
@@ -217,13 +245,13 @@ func convert(ctx context.Context, p printer.Printer) error {
 		// or an error.
 		if !r.HasArg(resource.WebhookURLArgKey) {
 			logger.DebugfOp(op, "no '%s' found, converting synchronously", resource.WebhookURLArgKey)
-			return convertSync(ctx, p, filename, fpath)
+			return convertSync(ctx, prinry, prnt, timeout, filename, fpath)
 		}
 		// as a webhook URL has been given, we
 		// run the following lines in a goroutine so that
 		// it doesn't block.
 		logger.DebugfOp(op, "'%s' found, converting asynchronously", resource.WebhookURLArgKey)
-		return convertAsync(ctx, p, filename, fpath)
+		return convertAsync(ctx, prinry, prnt, timeout, filename, fpath)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -231,13 +259,19 @@ func convert(ctx context.Context, p printer.Printer) error {
 	return nil
 }

-func convertSync(ctx context.Context, p printer.Printer, filename, fpath string) error {
+func convertSync(ctx context.Context, prinry *prinery.Prinery, prnt print.Print, timeout float64, filename, fpath string) error {
 	const op = "xhttp.convertSync"
+	logger := ctx.XLogger()
+	r := ctx.MustResource()
+	timeoutCtx, cancel := xcontext.WithTimeout(logger, timeout)
+	defer cancel()
 	resolver := func() error {
-		logger := ctx.XLogger()
-		r := ctx.MustResource()
-
-		if err := p.Print(fpath); err != nil {
+		if prinry == nil {
+			// case: merge.
+			if err := prnt.Print(timeoutCtx, fpath, nil); err != nil {
+				return err
+			}
+		} else if err := prinry.PrintRequest(timeoutCtx, logger, prnt, fpath); err != nil {
 			return err
 		}
 		if !r.HasArg(resource.ResultFilenameArgKey) {
@@ -267,12 +301,15 @@ func convertSync(ctx context.Context, p printer.Printer, filename, fpath string)
 		return nil
 	}
 	if err := resolver(); err != nil {
-		return xerror.New(op, err)
+		return xcontext.MustHandleError(
+			timeoutCtx,
+			xerror.New(op, err),
+		)
 	}
 	return nil
 }

-func convertAsync(ctx context.Context, p printer.Printer, filename, fpath string) error {
+func convertAsync(ctx context.Context, prinry *prinery.Prinery, prnt print.Print, timeout float64, filename, fpath string) error {
 	const op = "xhttp.convertAsync"
 	logger := ctx.XLogger()
 	r := ctx.MustResource()
@@ -286,7 +323,16 @@ func convertAsync(ctx context.Context, p printer.Printer, filename, fpath string
 	}
 	go func() {
 		defer r.Close() // nolint: errcheck
-		if err := p.Print(fpath); err != nil {
+		timeoutCtx, cancel := xcontext.WithTimeout(logger, timeout)
+		defer cancel()
+		if prinry == nil {
+			// case: merge.
+			if err := prnt.Print(timeoutCtx, fpath, nil); err != nil {
+				xerr := xerror.New(op, err)
+				logger.ErrorOp(xerror.Op(xerr), xerr)
+				return
+			}
+		} else if err := prinry.PrintRequest(timeoutCtx, logger, prnt, fpath); err != nil {
 			xerr := xerror.New(op, err)
 			logger.ErrorOp(xerror.Op(xerr), xerr)
 			return
--- a/internal/app/xhttp/handler_test.go
+++ b/internal/app/xhttp/handler_test.go
@@ -19,8 +19,8 @@ import (
 func TestPingHandler(t *testing.T) {
 	// should return 200.
 	config := conf.DefaultConfig()
-	srv := New(config)
-	srv = New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	req := httptest.NewRequest(http.MethodGet, pingEndpoint, nil)
 	test.AssertStatusCode(t, http.StatusOK, srv, req)
 	// should returns a JSON as
@@ -28,7 +28,8 @@ func TestPingHandler(t *testing.T) {
 	os.Setenv(conf.LogLevelEnvVar, "DEBUG")
 	config, err := conf.FromEnv()
 	assert.Nil(t, err)
-	srv = New(config)
+	// TODO
+	srv = New(config, nil, nil)
 	req = httptest.NewRequest(http.MethodGet, pingEndpoint, nil)
 	rec := httptest.NewRecorder()
 	srv.ServeHTTP(rec, req)
@@ -39,7 +40,8 @@ func TestPingHandler(t *testing.T) {

 func TestMergeHandler(t *testing.T) {
 	config := conf.DefaultConfig()
-	srv := New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	// should return 200.
 	body, contentType := test.MergeMultipartForm(t, nil)
 	req := httptest.NewRequest(http.MethodPost, mergeEndpoint, body)
@@ -72,7 +74,8 @@ func TestMergeHandler(t *testing.T) {

 func TestHTMLHandler(t *testing.T) {
 	config := conf.DefaultConfig()
-	srv := New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	endpoint := fmt.Sprintf("%s%s", convertGroupEndpoint, htmlEndpoint)
 	// should return 200.
 	body, contentType := test.HTMLMultipartForm(t, nil)
@@ -202,7 +205,8 @@ func TestHTMLHandler(t *testing.T) {

 func TestURLHandler(t *testing.T) {
 	config := conf.DefaultConfig()
-	srv := New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	endpoint := fmt.Sprintf("%s%s", convertGroupEndpoint, urlEndpoint)
 	// should return 200.
 	body, contentType := test.URLMultipartForm(t, nil)
@@ -332,7 +336,8 @@ func TestURLHandler(t *testing.T) {

 func TestMarkdownHandler(t *testing.T) {
 	config := conf.DefaultConfig()
-	srv := New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	endpoint := fmt.Sprintf("%s%s", convertGroupEndpoint, markdownEndpoint)
 	// should return 200.
 	body, contentType := test.MarkdownMultipartForm(t, nil)
@@ -462,7 +467,8 @@ func TestMarkdownHandler(t *testing.T) {

 func TestOfficeHandler(t *testing.T) {
 	config := conf.DefaultConfig()
-	srv := New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	endpoint := fmt.Sprintf("%s%s", convertGroupEndpoint, officeEndpoint)
 	// should return 200.
 	body, contentType := test.OfficeMultipartForm(t, nil)
@@ -524,7 +530,8 @@ func TestWebhook(t *testing.T) {
 		rcv.Start(":3001")
 	}()
 	config := conf.DefaultConfig()
-	srv := New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	// our custom server should receive the PDF.
 	body, contentType := test.MergeMultipartForm(t, map[string]string{string(resource.WebhookURLArgKey): "http://localhost:3001/foo"})
 	req := httptest.NewRequest(http.MethodPost, mergeEndpoint, body)
@@ -536,7 +543,8 @@ func TestWebhook(t *testing.T) {

 func TestResultFilename(t *testing.T) {
 	config := conf.DefaultConfig()
-	srv := New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	body, contentType := test.MergeMultipartForm(t, map[string]string{string(resource.ResultFilenameArgKey): "foo.pdf"})
 	req := httptest.NewRequest(http.MethodPost, mergeEndpoint, body)
 	req.Header.Set(echo.HeaderContentType, contentType)
--- a/internal/app/xhttp/middleware.go
+++ b/internal/app/xhttp/middleware.go
@@ -7,7 +7,8 @@ import (
 	"github.com/thecodingmachine/gotenberg/internal/app/xhttp/pkg/context"
 	"github.com/thecodingmachine/gotenberg/internal/app/xhttp/pkg/resource"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
-	"github.com/thecodingmachine/gotenberg/internal/pkg/pm2"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/prinery"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/process"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xrand"
@@ -15,7 +16,12 @@ import (

 // contextMiddleware extends the default echo.Context with
 // our custom context.Context.
-func contextMiddleware(config conf.Config, processes ...pm2.Process) echo.MiddlewareFunc {
+func contextMiddleware(
+	config conf.Config,
+	manager process.Manager,
+	chromePrinery *prinery.Prinery,
+	sofficePrinery *prinery.Prinery,
+) echo.MiddlewareFunc {
 	return func(next echo.HandlerFunc) echo.HandlerFunc {
 		return func(c echo.Context) error {
 			// generate a unique identifier for the request.
@@ -25,7 +31,7 @@ func contextMiddleware(config conf.Config, processes ...pm2.Process) echo.Middle
 			logger := xlog.New(config.LogLevel(), trace)
 			// extend the current echo context with our custom
 			// context.
-			ctx := context.New(c, logger, config, processes...)
+			ctx := context.New(c, logger, config, manager, chromePrinery, sofficePrinery)
 			// if its an healthcheck request, there
 			// is no need to create a Resource.
 			if ctx.Path() == pingEndpoint {
--- a/internal/app/xhttp/option.go
+++ b/internal/app/xhttp/option.go
@@ -3,53 +3,37 @@ package xhttp
 import (
 	"github.com/thecodingmachine/gotenberg/internal/app/xhttp/pkg/resource"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
-	"github.com/thecodingmachine/gotenberg/internal/pkg/printer"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/print"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
 )

-func mergePrinterOptions(r resource.Resource, config conf.Config) (printer.MergePrinterOptions, error) {
-	const op string = "xhttp.mergePrinterOptions"
-	waitTimeout, err := resource.WaitTimeoutArg(r, config)
-	if err != nil {
-		return printer.MergePrinterOptions{}, xerror.New(op, err)
-	}
-	return printer.MergePrinterOptions{
-		WaitTimeout: waitTimeout,
-	}, nil
-}
-
-func chromePrinterOptions(r resource.Resource, config conf.Config) (printer.ChromePrinterOptions, error) {
-	const op string = "xhttp.chromePrinterOptions"
-	resolver := func() (printer.ChromePrinterOptions, error) {
-		waitTimeout, err := resource.WaitTimeoutArg(r, config)
-		if err != nil {
-			return printer.ChromePrinterOptions{}, err
-		}
+func chromePrintOptions(r resource.Resource, config conf.Config) (print.ChromePrintOptions, error) {
+	const op string = "xhttp.chromePrintOptions"
+	resolver := func() (print.ChromePrintOptions, error) {
 		waitDelay, err := resource.WaitDelayArg(r, config)
 		if err != nil {
-			return printer.ChromePrinterOptions{}, err
+			return print.ChromePrintOptions{}, err
 		}
 		headerHTML, footerHTML,
 			err := resource.HeaderFooterContents(r, config)
 		if err != nil {
-			return printer.ChromePrinterOptions{}, err
+			return print.ChromePrintOptions{}, err
 		}
 		paperWidth, paperHeight,
 			err := resource.PaperSizeArgs(r, config)
 		if err != nil {
-			return printer.ChromePrinterOptions{}, err
+			return print.ChromePrintOptions{}, err
 		}
 		marginTop, marginBottom, marginLeft, marginRight,
 			err := resource.MarginArgs(r, config)
 		if err != nil {
-			return printer.ChromePrinterOptions{}, err
+			return print.ChromePrintOptions{}, err
 		}
 		landscape, err := r.BoolArg(resource.LandscapeArgKey, false)
 		if err != nil {
-			return printer.ChromePrinterOptions{}, err
+			return print.ChromePrintOptions{}, err
 		}
-		return printer.ChromePrinterOptions{
-			WaitTimeout:  waitTimeout,
+		return print.ChromePrintOptions{
 			WaitDelay:    waitDelay,
 			HeaderHTML:   headerHTML,
 			FooterHTML:   footerHTML,
@@ -69,20 +53,15 @@ func chromePrinterOptions(r resource.Resource, config conf.Config) (printer.Chro
 	return opts, nil
 }

-func officePrinterOptions(r resource.Resource, config conf.Config) (printer.OfficePrinterOptions, error) {
-	const op string = "xhttp.officePrinterOptions"
-	resolver := func() (printer.OfficePrinterOptions, error) {
-		waitTimeout, err := resource.WaitTimeoutArg(r, config)
-		if err != nil {
-			return printer.OfficePrinterOptions{}, err
-		}
+func officePrintOptions(r resource.Resource, config conf.Config) (print.OfficePrintOptions, error) {
+	const op string = "xhttp.officePrintOptions"
+	resolver := func() (print.OfficePrintOptions, error) {
 		landscape, err := r.BoolArg(resource.LandscapeArgKey, false)
 		if err != nil {
-			return printer.OfficePrinterOptions{}, err
+			return print.OfficePrintOptions{}, err
 		}
-		return printer.OfficePrinterOptions{
-			WaitTimeout: waitTimeout,
-			Landscape:   landscape,
+		return print.OfficePrintOptions{
+			Landscape: landscape,
 		}, nil
 	}
 	opts, err := resolver()
--- a/internal/app/xhttp/pkg/context/context.go
+++ b/internal/app/xhttp/pkg/context/context.go
@@ -13,7 +13,8 @@ import (
 	"github.com/thecodingmachine/gotenberg/internal/app/xhttp/pkg/resource"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/normalize"
-	"github.com/thecodingmachine/gotenberg/internal/pkg/pm2"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/prinery"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/process"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
 )
@@ -21,20 +22,31 @@ import (
 // Context extends the default echo.Context.
 type Context struct {
 	echo.Context
-	logger    xlog.Logger
-	config    conf.Config
-	processes []pm2.Process
-	resource  resource.Resource
-	startTime time.Time
+	logger         xlog.Logger
+	config         conf.Config
+	manager        process.Manager
+	chromePrinery  *prinery.Prinery
+	sofficePrinery *prinery.Prinery
+	resource       resource.Resource
+	startTime      time.Time
 }

 // New creates a new Context.
-func New(c echo.Context, logger xlog.Logger, config conf.Config, processes ...pm2.Process) Context {
+func New(
+	c echo.Context,
+	logger xlog.Logger,
+	config conf.Config,
+	manager process.Manager,
+	chromePrinery *prinery.Prinery,
+	sofficePrinery *prinery.Prinery,
+) Context {
 	return Context{
 		c,
 		logger,
 		config,
-		processes,
+		manager,
+		chromePrinery,
+		sofficePrinery,
 		resource.Resource{},
 		time.Now(),
 	}
@@ -77,17 +89,52 @@ func (ctx Context) Config() conf.Config {
 // one of the processes is not viable.
 func (ctx Context) ProcessesHealthcheck() error {
 	const op string = "context.Context.ProcessesHealthcheck"
-	for _, process := range ctx.processes {
-		if !process.IsViable() {
+	processes := ctx.manager.All()
+	for _, p := range processes {
+		if !ctx.manager.IsViable(p) {
 			return xerror.New(
 				op,
-				fmt.Errorf("'%s' is not viable", process.Fullname()),
+				fmt.Errorf("'%s' is not viable", p.ID()),
 			)
 		}
 	}
 	return nil
 }

+/*
+MustChromePrinery returns the instance of
+prinery.Prinery associated with the Context.
+
+This prinery.Prinery handles Google Chrome
+headless.
+
+It panics if no instance of prinery.Prinery.
+*/
+func (ctx Context) MustChromePrinery() *prinery.Prinery {
+	const op string = "context.Context.MustChromePrinery"
+	if ctx.chromePrinery == nil {
+		panic(fmt.Sprintf("%s: unable to retrieve the instance of Google Chrome Headless prinery.Prinery from our custom context.Context", op))
+	}
+	return ctx.chromePrinery
+}
+
+/*
+MustSofficePrinery returns the instance of
+prinery.Prinery associated with the Context.
+
+This prinery.Prinery handles LibreOffice
+headless.
+
+It panics if no instance of prinery.Prinery.
+*/
+func (ctx Context) MustSofficePrinery() *prinery.Prinery {
+	const op string = "context.Context.MustSofficePrinery"
+	if ctx.sofficePrinery == nil {
+		panic(fmt.Sprintf("%s: unable to retrieve the instance of LibreOffice Headless prinery.Prinery from our custom context.Context", op))
+	}
+	return ctx.sofficePrinery
+}
+
 // WithResource creates a resource.Resource and
 // adds it to the Context.
 func (ctx *Context) WithResource(directoryName string) error {
--- a/internal/app/xhttp/pkg/resource/arg.go
+++ b/internal/app/xhttp/pkg/resource/arg.go
@@ -76,6 +76,34 @@ func ArgKeys() []ArgKey {
 	}
 }

+/*
+WaitTimeoutAndWaitDelayArg is a helper for retrieving
+the sum of "waitTimeout" and "waitDelay" arguments
+as float64.
+
+It also validates them against the application
+configuration.
+*/
+func WaitTimeoutAndWaitDelayArg(r Resource, config conf.Config) (float64, error) {
+	const op string = "resource.WaitTimeoutAndWaitDelayArg"
+	resolver := func() (float64, error) {
+		waitTimeout, err := WaitTimeoutArg(r, config)
+		if err != nil {
+			return waitTimeout, err
+		}
+		waitDelay, err := WaitDelayArg(r, config)
+		if err != nil {
+			return waitDelay, err
+		}
+		return waitTimeout + waitDelay, nil
+	}
+	combined, err := resolver()
+	if err != nil {
+		return combined, xerror.New(op, err)
+	}
+	return combined, nil
+}
+
 /*
 WaitTimeoutArg is a helper for retrieving
 the "waitTimeout" argument as float64.
--- a/internal/app/xhttp/xhttp.go
+++ b/internal/app/xhttp/xhttp.go
@@ -3,15 +3,21 @@ package xhttp
 import (
 	"github.com/labstack/echo/v4"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
-	"github.com/thecodingmachine/gotenberg/internal/pkg/pm2"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/prinery"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/process"
 )

 // New returns a custom echo.Echo.
-func New(config conf.Config, processes ...pm2.Process) *echo.Echo {
+func New(
+	config conf.Config,
+	manager process.Manager,
+	chromePrinery *prinery.Prinery,
+	sofficePrinery *prinery.Prinery,
+) *echo.Echo {
 	srv := echo.New()
 	srv.HideBanner = true
 	srv.HidePort = true
-	srv.Use(contextMiddleware(config, processes...))
+	srv.Use(contextMiddleware(config, manager, chromePrinery, sofficePrinery))
 	srv.Use(loggerMiddleware())
 	srv.Use(cleanupMiddleware())
 	srv.Use(errorMiddleware())
--- a/internal/app/xhttp/xhttp_test.go
+++ b/internal/app/xhttp/xhttp_test.go
@@ -17,7 +17,8 @@ func TestDisableChromeEndpoints(t *testing.T) {
 	os.Setenv(conf.DisableGoogleChromeEnvVar, "1")
 	config, err := conf.FromEnv()
 	assert.Nil(t, err)
-	srv := New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	// Ping endpoint should return 200.
 	req := httptest.NewRequest(http.MethodGet, pingEndpoint, nil)
 	test.AssertStatusCode(t, http.StatusOK, srv, req)
@@ -54,7 +55,8 @@ func TestDisableUnoconvEndpoints(t *testing.T) {
 	os.Setenv(conf.DisableUnoconvEnvVar, "1")
 	config, err := conf.FromEnv()
 	assert.Nil(t, err)
-	srv := New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	// Ping endpoint should return 200.
 	req := httptest.NewRequest(http.MethodGet, pingEndpoint, nil)
 	test.AssertStatusCode(t, http.StatusOK, srv, req)
@@ -91,7 +93,8 @@ func TestDisableChromeAndUnoconvEndpoints(t *testing.T) {
 	os.Setenv(conf.DisableUnoconvEnvVar, "1")
 	config, err := conf.FromEnv()
 	assert.Nil(t, err)
-	srv := New(config)
+	// TODO
+	srv := New(config, nil, nil)
 	// Ping endpoint should return 200.
 	req := httptest.NewRequest(http.MethodGet, pingEndpoint, nil)
 	test.AssertStatusCode(t, http.StatusOK, srv, req)
--- a/internal/pkg/prinery/doc.go
+++ b/internal/pkg/prinery/doc.go
@@ -0,0 +1 @@
+package prinery
--- a/internal/pkg/prinery/prinery.go
+++ b/internal/pkg/prinery/prinery.go
@@ -0,0 +1,123 @@
+package prinery
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/print"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/process"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+)
+
+type request struct {
+	ctx    context.Context
+	logger xlog.Logger
+	print  print.Print
+	dest   string
+	result chan error
+}
+
+type worker struct {
+	work chan request
+	proc process.Process
+}
+
+func (w *worker) do(done chan *worker) {
+	for {
+		req := <-w.work
+		req.result <- req.print.Print(req.ctx, req.dest, w.proc)
+		done <- w
+	}
+}
+
+type Prinery struct {
+	logger  xlog.Logger
+	manager process.Manager
+	work    chan request
+	pool    chan *worker
+	done    chan *worker
+}
+
+func New(logger xlog.Logger, manager process.Manager, key process.Key) (*Prinery, error) {
+	const op string = "prinery.New"
+	processes := manager.Processes(key)
+	nWorkers := len(processes)
+	if nWorkers == 0 {
+		err := fmt.Errorf("no processes found for key '%s'", string(key))
+		return nil, xerror.New(op, err)
+	}
+	logger.DebugfOp(op, "found '%d' processes for key '%s'", nWorkers, string(key))
+	work := make(chan request, 1)
+	pool := make(chan *worker, nWorkers)
+	done := make(chan *worker, nWorkers)
+	for _, p := range processes {
+		w := &worker{
+			work: work,
+			proc: p,
+		}
+		pool <- w
+		go w.do(done)
+	}
+	return &Prinery{
+		logger:  logger,
+		manager: manager,
+		work:    work,
+		pool:    pool,
+		done:    done,
+	}, nil
+}
+
+func (p *Prinery) PrintRequest(ctx context.Context, logger xlog.Logger, prnt print.Print, dest string) error {
+	const op string = "prinery.Prinery.PrintRequest"
+	req := request{
+		ctx:    ctx,
+		logger: logger,
+		print:  prnt,
+		dest:   dest,
+		result: make(chan error),
+	}
+	p.dispatch(req)
+	err := <-req.result
+	if err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (p *Prinery) Start() {
+	for {
+		select {
+		case req := <-p.work:
+			p.dispatch(req)
+		case w := <-p.done:
+			p.completed(w)
+		}
+	}
+}
+
+func (p *Prinery) dispatch(req request) {
+	const op string = "prinery.Prinery.dispatch"
+	select {
+	case w := <-p.pool:
+		w.work <- req
+	case <-req.ctx.Done():
+		req.result <- xerror.New(op, req.ctx.Err())
+	}
+}
+
+func (p *Prinery) completed(w *worker) {
+	const op string = "prinery.Prinerty.completed"
+	go func() {
+		// check process viability.
+		isViable := p.manager.IsViable(w.proc)
+		// check process memory usage.
+		// TODO handle error.
+		memory, _ := p.manager.Memory(w.proc)
+		p.logger.DebugfOp(op, "%s: isViable = %t, memory = %d", w.proc.ID(), isViable, memory)
+		// TODO manage viability and memory usage.
+		// pushing back the worker.
+		p.pool <- w
+	}()
+
+}
--- a/internal/pkg/print/chrome.go
+++ b/internal/pkg/print/chrome.go
@@ -0,0 +1,265 @@
+package print
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"time"
+
+	"github.com/mafredri/cdp"
+	"github.com/mafredri/cdp/devtool"
+	"github.com/mafredri/cdp/protocol/network"
+	"github.com/mafredri/cdp/protocol/page"
+	"github.com/mafredri/cdp/protocol/target"
+	"github.com/mafredri/cdp/rpcc"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/process"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerrgroup"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xtime"
+)
+
+type chromePrint struct {
+	logger xlog.Logger
+	url    string
+	opts   ChromePrintOptions
+}
+
+// ChromePrintOptions helps customizing the
+// Google Chrome Print result.
+type ChromePrintOptions struct {
+	WaitDelay    float64
+	HeaderHTML   string
+	FooterHTML   string
+	PaperWidth   float64
+	PaperHeight  float64
+	MarginTop    float64
+	MarginBottom float64
+	MarginLeft   float64
+	MarginRight  float64
+	Landscape    bool
+}
+
+// DefaultChromePrintOptions returns the default
+// Google Chrome Print options.
+func DefaultChromePrintOptions() ChromePrintOptions {
+	const defaultHeaderFooterHTML string = "<html><head></head><body></body></html>"
+	return ChromePrintOptions{
+		WaitDelay:    0.0,
+		HeaderHTML:   defaultHeaderFooterHTML,
+		FooterHTML:   defaultHeaderFooterHTML,
+		PaperWidth:   8.27,
+		PaperHeight:  11.7,
+		MarginTop:    1.0,
+		MarginBottom: 1.0,
+		MarginLeft:   1.0,
+		MarginRight:  1.0,
+		Landscape:    false,
+	}
+}
+
+func (p chromePrint) Print(ctx context.Context, dest string, proc process.Process) error {
+	const op string = "print.chromePrint.Print"
+	resolver := func() error {
+		devtEndpoint := fmt.Sprintf("http://%s:%d", proc.Host(), proc.Port())
+		devt, err := devtool.New(devtEndpoint).Version(ctx)
+		if err != nil {
+			return err
+		}
+		// connect to WebSocket URL (page) that speaks the Chrome DevTools Protocol.
+		devtConn, err := rpcc.DialContext(ctx, devt.WebSocketDebuggerURL)
+		if err != nil {
+			return err
+		}
+		defer devtConn.Close() // nolint: errcheck
+		// create a new CDP Client that uses conn.
+		devtClient := cdp.NewClient(devtConn)
+		newContextTarget, err := devtClient.Target.CreateBrowserContext(ctx)
+		if err != nil {
+			return err
+		}
+		/*
+			close the browser context when done.
+			we're not using the "default" context
+			as it may timeout before actually closing
+			the browser context.
+			see: https://github.com/mafredri/cdp/issues/101#issuecomment-524533670
+		*/
+		disposeBrowserContextArgs := target.NewDisposeBrowserContextArgs(newContextTarget.BrowserContextID)
+		defer devtClient.Target.DisposeBrowserContext(context.Background(), disposeBrowserContextArgs) // nolint: errcheck
+		// create a new blank target with the new browser context.
+		createTargetArgs := target.
+			NewCreateTargetArgs("about:blank").
+			SetBrowserContextID(newContextTarget.BrowserContextID)
+		newTarget, err := devtClient.Target.CreateTarget(ctx, createTargetArgs)
+		if err != nil {
+			return err
+		}
+		// connect the client to the new target.
+		newTargetWsURL := fmt.Sprintf("ws://%s:%d/devtools/page/%s", proc.Host(), proc.Port(), newTarget.TargetID)
+		newContextConn, err := rpcc.DialContext(ctx, newTargetWsURL)
+		if err != nil {
+			return err
+		}
+		defer newContextConn.Close() // nolint: errcheck
+		// create a new CDP Client that uses newContextConn.
+		targetClient := cdp.NewClient(newContextConn)
+		/*
+			close the target when done.
+			we're not using the "default" context
+			as it may timeout before actually closing
+			the target.
+			see: https://github.com/mafredri/cdp/issues/101#issuecomment-524533670
+		*/
+		closeTargetArgs := target.NewCloseTargetArgs(newTarget.TargetID)
+		defer targetClient.Target.CloseTarget(context.Background(), closeTargetArgs) // nolint: errcheck
+		// enable all events.
+		if err := p.enableEvents(ctx, targetClient); err != nil {
+			return err
+		}
+		// listen for all events.
+		if err := p.listenEvents(ctx, targetClient); err != nil {
+			return err
+		}
+		// apply a wait delay (if any).
+		if p.opts.WaitDelay > 0.0 {
+			// wait for a given amount of time (useful for javascript delay).
+			p.logger.DebugfOp(op, "applying a wait delay of '%.2fs'...", p.opts.WaitDelay)
+			time.Sleep(xtime.Duration(p.opts.WaitDelay))
+		} else {
+			p.logger.DebugOp(op, "no wait delay to apply, moving on...")
+		}
+		// print the page to PDF.
+		print, err := targetClient.Page.PrintToPDF(
+			ctx,
+			page.NewPrintToPDFArgs().
+				SetPaperWidth(p.opts.PaperWidth).
+				SetPaperHeight(p.opts.PaperHeight).
+				SetMarginTop(p.opts.MarginTop).
+				SetMarginBottom(p.opts.MarginBottom).
+				SetMarginLeft(p.opts.MarginLeft).
+				SetMarginRight(p.opts.MarginRight).
+				SetLandscape(p.opts.Landscape).
+				SetDisplayHeaderFooter(true).
+				SetHeaderTemplate(p.opts.HeaderHTML).
+				SetFooterTemplate(p.opts.FooterHTML).
+				SetPrintBackground(true),
+		)
+		if err != nil {
+			return err
+		}
+		if err := ioutil.WriteFile(dest, print.Data, 0644); err != nil {
+			return err
+		}
+		return nil
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (p chromePrint) enableEvents(ctx context.Context, client *cdp.Client) error {
+	const op string = "print.chromePrint.enableEvents"
+	// enable all the domain events that we're interested in.
+	if err := xerrgroup.Run(
+		func() error { return client.DOM.Enable(ctx) },
+		func() error { return client.Network.Enable(ctx, network.NewEnableArgs()) },
+		func() error { return client.Page.Enable(ctx) },
+		func() error {
+			return client.Page.SetLifecycleEventsEnabled(ctx, page.NewSetLifecycleEventsEnabledArgs(true))
+		},
+		func() error { return client.Runtime.Enable(ctx) },
+	); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (p chromePrint) listenEvents(ctx context.Context, client *cdp.Client) error {
+	const op string = "print.chromePrint.listenEvents"
+	resolver := func() error {
+		// make sure Page events are enabled.
+		if err := client.Page.Enable(ctx); err != nil {
+			return err
+		}
+		// make sure Network events are enabled.
+		if err := client.Network.Enable(ctx, nil); err != nil {
+			return err
+		}
+		// create all clients for events.
+		domContentEventFired, err := client.Page.DOMContentEventFired(ctx)
+		if err != nil {
+			return err
+		}
+		defer domContentEventFired.Close() // nolint: errcheck
+		loadEventFired, err := client.Page.LoadEventFired(ctx)
+		if err != nil {
+			return err
+		}
+		defer loadEventFired.Close() // nolint: errcheck
+		lifecycleEvent, err := client.Page.LifecycleEvent(ctx)
+		if err != nil {
+			return err
+		}
+		defer lifecycleEvent.Close() // nolint: errcheck
+		loadingFinished, err := client.Network.LoadingFinished(ctx)
+		if err != nil {
+			return err
+		}
+		defer loadingFinished.Close() // nolint: errcheck
+		if _, err := client.Page.Navigate(ctx, page.NewNavigateArgs(p.url)); err != nil {
+			return err
+		}
+		// wait for all events.
+		return xerrgroup.Run(
+			func() error {
+				_, err := domContentEventFired.Recv()
+				if err != nil {
+					return err
+				}
+				p.logger.DebugOp(op, "event 'domContentEventFired' received")
+				return nil
+			},
+			func() error {
+				_, err := loadEventFired.Recv()
+				if err != nil {
+					return err
+				}
+				p.logger.DebugOp(op, "event 'loadEventFired' received")
+				return nil
+			},
+			func() error {
+				const networkIdleEventName string = "networkIdle"
+				for {
+					ev, err := lifecycleEvent.Recv()
+					if err != nil {
+						return err
+					}
+					p.logger.DebugfOp(op, "event '%s' received", ev.Name)
+					if ev.Name == networkIdleEventName {
+						break
+					}
+				}
+				return nil
+			},
+			func() error {
+				_, err := loadingFinished.Recv()
+				if err != nil {
+					return err
+				}
+				p.logger.DebugOp(op, "event 'loadingFinished' received")
+				return nil
+			},
+		)
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Print(new(chromePrint))
+)
--- a/internal/pkg/print/doc.go
+++ b/internal/pkg/print/doc.go
@@ -0,0 +1 @@
+package print
--- a/internal/pkg/print/html.go
+++ b/internal/pkg/print/html.go
@@ -0,0 +1,18 @@
+package print
+
+import (
+	"fmt"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+)
+
+// NewHTMLPrint returns a Print for
+// converting an HTML file to PDF.
+func NewHTMLPrint(logger xlog.Logger, fpath string, opts ChromePrintOptions) Print {
+	URL := fmt.Sprintf("file://%s", fpath)
+	return chromePrint{
+		logger: logger,
+		url:    URL,
+		opts:   opts,
+	}
+}
--- a/internal/pkg/print/markdown.go
+++ b/internal/pkg/print/markdown.go
@@ -0,0 +1,70 @@
+package print
+
+import (
+	"bytes"
+	"fmt"
+	"html/template"
+	"io/ioutil"
+	"path/filepath"
+
+	"github.com/microcosm-cc/bluemonday"
+	"github.com/russross/blackfriday/v2"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xrand"
+)
+
+// NewMarkdownPrint returns a Print for
+// converting a Markdown file to PDF.
+func NewMarkdownPrint(logger xlog.Logger, fpath string, opts ChromePrintOptions) (Print, error) {
+	const op string = "print.NewMarkdownPrint"
+	resolver := func() (string, error) {
+		tmpl, err := template.
+			New(filepath.Base(fpath)).
+			Funcs(template.FuncMap{"toHTML": markdownToHTML}).
+			ParseFiles(fpath)
+		if err != nil {
+			return "", err
+		}
+		dirPath := filepath.Dir(fpath)
+		data := &templateData{DirPath: dirPath}
+		logger.DebugOp(op, "converting Markdown files to HTML...")
+		var buffer bytes.Buffer
+		if err := tmpl.Execute(&buffer, data); err != nil {
+			return "", err
+		}
+		baseFilename := xrand.Get()
+		dst := fmt.Sprintf("%s/%s.html", dirPath, baseFilename)
+		logger.DebugOp(op, "writing the HTML from previous conversion(s) into new file...")
+		if err := ioutil.WriteFile(dst, buffer.Bytes(), 0644); err != nil {
+			return "", err
+		}
+		return fmt.Sprintf("file://%s", dst), nil
+	}
+	URL, err := resolver()
+	if err != nil {
+		return chromePrint{}, xerror.New(op, err)
+	}
+	return chromePrint{
+		logger: logger,
+		url:    URL,
+		opts:   opts,
+	}, nil
+}
+
+type templateData struct {
+	DirPath string
+}
+
+func markdownToHTML(dirPath, filename string) (template.HTML, error) {
+	const op string = "print.markdownToHTML"
+	fpath := fmt.Sprintf("%s/%s", dirPath, filename)
+	b, err := ioutil.ReadFile(fpath)
+	if err != nil {
+		return "", xerror.New(op, err)
+	}
+	unsafe := blackfriday.Run(b)
+	content := bluemonday.UGCPolicy().SanitizeBytes(unsafe)
+	/* #nosec */
+	return template.HTML(content), nil
+}
--- a/internal/pkg/print/merge.go
+++ b/internal/pkg/print/merge.go
@@ -0,0 +1,44 @@
+package print
+
+import (
+	"context"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/process"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xexec"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+)
+
+type mergePrint struct {
+	logger xlog.Logger
+	fpaths []string
+}
+
+// NewMergePrint returns a Print for
+// merging PDF files.
+func NewMergePrint(logger xlog.Logger, fpaths []string) Print {
+	return mergePrint{
+		logger: logger,
+		fpaths: fpaths,
+	}
+}
+
+func (p mergePrint) Print(ctx context.Context, dest string, proc process.Process) error {
+	const op string = "print.mergePrint.Print"
+	p.logger.DebugfOp(op, "merging '%v'...", p.fpaths)
+	resolver := func() error {
+		var args []string
+		args = append(args, p.fpaths...)
+		args = append(args, "cat", "output", dest)
+		cmd, err := xexec.CommandContext(ctx, p.logger, "pdftk", args...)
+		if err != nil {
+			return err
+		}
+		xexec.LogBeforeExecute(p.logger, cmd)
+		return cmd.Run()
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
--- a/internal/pkg/print/office.go
+++ b/internal/pkg/print/office.go
@@ -0,0 +1,109 @@
+package print
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/process"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xexec"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xrand"
+)
+
+type officePrint struct {
+	logger xlog.Logger
+	fpaths []string
+	opts   OfficePrintOptions
+}
+
+// OfficePrintOptions helps customizing the
+// LibreOffice Print result.
+type OfficePrintOptions struct {
+	Landscape bool
+}
+
+// DefaultOfficePrinterOptions returns the default
+// LibreOffice Print options.
+func DefaultOfficePrinterOptions() OfficePrintOptions {
+	return OfficePrintOptions{
+		Landscape: false,
+	}
+}
+
+// NewOfficePrint returns a Print for
+// converting Office documents to PDF.
+func NewOfficePrint(logger xlog.Logger, fpaths []string, opts OfficePrintOptions) Print {
+	return officePrint{
+		logger: logger,
+		fpaths: fpaths,
+		opts:   opts,
+	}
+}
+
+func (p officePrint) Print(ctx context.Context, dest string, proc process.Process) error {
+	const op string = "print.officePrint.Print"
+	resolver := func() error {
+		fpaths := make([]string, len(p.fpaths))
+		dirPath := filepath.Dir(dest)
+		for i, fpath := range p.fpaths {
+			baseFilename := xrand.Get()
+			tmpDest := fmt.Sprintf("%s/%d%s.pdf", dirPath, i, baseFilename)
+			p.logger.DebugfOp(op, "converting '%s' to PDF...", fpath)
+			if err := unoconv(ctx, p.logger, fpath, tmpDest, p.opts); err != nil {
+				return err
+			}
+			p.logger.DebugfOp(op, "'%s.pdf' created", baseFilename)
+			fpaths[i] = tmpDest
+		}
+		if len(fpaths) == 1 {
+			p.logger.DebugOp(op, "only one PDF created, nothing to merge")
+			if err := os.Rename(fpaths[0], dest); err != nil {
+				return err
+			}
+			return nil
+		}
+		merger := NewMergePrint(p.logger, fpaths)
+		return merger.Print(ctx, dest, nil)
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func unoconv(ctx context.Context, logger xlog.Logger, fpath, dest string, opts OfficePrintOptions) error {
+	const op string = "print.unoconv"
+	resolver := func() error {
+		args := []string{
+			"--format",
+			"pdf",
+		}
+		if opts.Landscape {
+			args = append(args, "--printer", "PaperOrientation=landscape")
+		}
+		args = append(args, "--output", dest, fpath)
+		cmd, err := xexec.CommandContext(
+			ctx,
+			logger,
+			"unoconv",
+			args...,
+		)
+		if err != nil {
+			return err
+		}
+		xexec.LogBeforeExecute(logger, cmd)
+		return cmd.Run()
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Print(new(officePrint))
+)
--- a/internal/pkg/print/print.go
+++ b/internal/pkg/print/print.go
@@ -0,0 +1,13 @@
+package print
+
+import (
+	"context"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/process"
+)
+
+// Print is a type that can create a PDF file from a source.
+// The source is defined in the underlying implementation.
+type Print interface {
+	Print(ctx context.Context, dest string, proc process.Process) error
+}
--- a/internal/pkg/print/url.go
+++ b/internal/pkg/print/url.go
@@ -0,0 +1,15 @@
+package print
+
+import (
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+)
+
+// NewURLPrint returns a Print for
+// converting a URL to PDF.
+func NewURLPrint(logger xlog.Logger, url string, opts ChromePrintOptions) Print {
+	return chromePrint{
+		logger: logger,
+		url:    url,
+		opts:   opts,
+	}
+}
--- a/internal/pkg/process/chrome.go
+++ b/internal/pkg/process/chrome.go
@@ -0,0 +1,106 @@
+package process
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/mafredri/cdp/devtool"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+)
+
+const ChromeKey Key = "chrome"
+
+type chromeProcess struct {
+	id   string
+	host string
+	port int
+}
+
+// NewChromeProcess returns a Google Chrome
+// headless process.
+func NewChromeProcess(id, host string, port int) Process {
+	return chromeProcess{
+		id:   id,
+		host: host,
+		port: port,
+	}
+}
+
+func (p chromeProcess) ID() string {
+	return p.id
+}
+
+func (p chromeProcess) Host() string {
+	return p.host
+}
+
+func (p chromeProcess) Port() int {
+	return p.port
+}
+
+func (p chromeProcess) binary() string {
+	return "google-chrome-stable"
+}
+
+func (p chromeProcess) args() []string {
+	return []string{
+		"--no-sandbox",
+		"--headless",
+		// see https://github.com/GoogleChrome/puppeteer/issues/2410.
+		"--font-render-hinting=medium",
+		fmt.Sprintf("--remote-debugging-port=%d", p.port),
+		"--disable-gpu",
+		"--disable-translate",
+		"--disable-extensions",
+		"--disable-background-networking",
+		"--safebrowsing-disable-auto-update",
+		"--disable-sync",
+		"--disable-default-apps",
+		"--hide-scrollbars",
+		"--metrics-recording-only",
+		"--mute-audio",
+		"--no-first-run",
+	}
+}
+
+func (p chromeProcess) warmupTime() time.Duration {
+	return 10 * time.Second
+}
+
+func (p chromeProcess) viabilityFunc() func(logger xlog.Logger) bool {
+	const op string = "process.chromeProcess.viabilityFunc"
+	return func(logger xlog.Logger) bool {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		endpoint := fmt.Sprintf("http://%s:%d" /*p.host*/, "localhost", p.port)
+		logger.DebugfOp(
+			op,
+			"checking '%s' viability via endpoint '%s/json/version'",
+			p.ID(),
+			endpoint,
+		)
+		v, err := devtool.New(endpoint).Version(ctx)
+		if err != nil {
+			logger.ErrorfOp(
+				op,
+				"'%s' is not viable as endpoint returned '%v'",
+				p.ID(),
+				err,
+			)
+			return false
+		}
+		logger.DebugfOp(
+			op,
+			"'%s' is viable as endpoint returned '%v'",
+			p.ID(),
+			v,
+		)
+		return true
+	}
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Process(new(chromeProcess))
+)
--- a/internal/pkg/process/doc.go
+++ b/internal/pkg/process/doc.go
@@ -0,0 +1 @@
+package process
--- a/internal/pkg/process/pm2.go
+++ b/internal/pkg/process/pm2.go
@@ -0,0 +1,324 @@
+package process
+
+import (
+	"encoding/json"
+	"fmt"
+	"os/exec"
+	"sync"
+	"time"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xexec"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xtime"
+)
+
+type jlistItem struct {
+	Name   string `json:"name"`
+	PM2Env struct {
+		Status      string `json:"status"`
+		RestartTime int64  `json:"restart_time"`
+	} `json:"pm2_env"`
+	Monit struct {
+		Memory int64   `json:"memory"`
+		CPU    float64 `json:"cpu"`
+	} `json:"monit"`
+}
+
+type jlist []jlistItem
+
+func (list jlist) toList() List {
+	var result List
+	for _, current := range list {
+		item := ListItem{
+			Name:    current.Name,
+			Status:  current.PM2Env.Status,
+			Restart: current.PM2Env.RestartTime,
+			Memory:  current.Monit.Memory, // TODO humanize?
+			CPU:     current.Monit.CPU,
+		}
+		result = append(result, item)
+	}
+	return result
+}
+
+func (list jlist) isOnline(p Process) bool {
+	const onlineStatus string = "online"
+	for _, item := range list {
+		if item.Name == p.ID() {
+			return item.PM2Env.Status == onlineStatus
+		}
+	}
+	return false
+}
+
+func (list jlist) memory(p Process) (int64, error) {
+	const op string = "process.jlist.memory"
+	for _, item := range list {
+		if item.Name == p.ID() {
+			return item.Monit.Memory, nil
+		}
+	}
+	return 0, xerror.New(
+		op,
+		fmt.Errorf("'%s' does not exist in the list of PM2 processes", p.ID()),
+	)
+}
+
+type command string
+
+const (
+	startCommand   command = "start"
+	restartCommand command = "restart"
+	stopCommand    command = "stop"
+	logsCommand    command = "logs"
+	jlistCommand   command = "jlist"
+)
+
+const maximumRestartAttempts uint = 3
+
+type pm2Manager struct {
+	logger   xlog.Logger
+	config   conf.Config
+	pool     map[Key][]Process
+	list     *jlist
+	listLock *sync.Mutex
+}
+
+// NewPM2Manager returns a PM2 manager.
+func NewPM2Manager(logger xlog.Logger, config conf.Config) Manager {
+	const op string = "process.NewPM2Manager"
+	m := &pm2Manager{
+		logger:   logger,
+		config:   config,
+		pool:     make(map[Key][]Process),
+		listLock: &sync.Mutex{},
+	}
+	if !config.DisableGoogleChrome() {
+		processes := make([]Process, 2)
+		availablePort := 9222
+		// TODO from config
+		for i := 0; i < 2; i++ {
+			proc := chromeProcess{
+				host: "127.0.0.1",
+				port: availablePort,
+			}
+			proc.id = fmt.Sprintf("%s-%d", proc.binary(), proc.port)
+			processes[i] = proc
+			logger.DebugfOp(op, "added new process %v", proc)
+			availablePort++
+		}
+		m.pool[ChromeKey] = processes
+	}
+	if !config.DisableUnoconv() {
+		processes := make([]Process, 2)
+		availablePort := 2002
+		// TODO from config
+		for i := 0; i < 2; i++ {
+			proc := sofficeProcess{
+				host: "127.0.0.1",
+				port: availablePort,
+			}
+			proc.id = fmt.Sprintf("%s-%d", proc.binary(), proc.port)
+			processes[i] = proc
+			logger.DebugfOp(op, "added new process %v", proc)
+			availablePort++
+		}
+		m.pool[SofficeKey] = processes
+	}
+	// update the manager processes list
+	// only if there are processes.
+	if !config.DisableGoogleChrome() || !config.DisableUnoconv() {
+		go m.jlistTimer()
+	}
+	return m
+}
+
+func (m *pm2Manager) jlistTimer() {
+	const op string = "process.pm2Manager.jlistTimer"
+	duration := xtime.Duration(10)
+	resolver := func() error {
+		m.listLock.Lock()
+		defer m.listLock.Unlock()
+		out, err := exec.
+			Command("pm2", string(jlistCommand)).
+			Output()
+		if err != nil {
+			return err
+		}
+		data := &jlist{}
+		if err := json.Unmarshal(out, data); err != nil {
+			return err
+		}
+		m.list = data
+		return nil
+	}
+	// update every x seconds the
+	// list from the manager.
+	for range time.Tick(duration) {
+		if err := resolver(); err != nil {
+			m.logger.ErrorOp(op, xerror.New(op, err))
+		}
+	}
+}
+
+func (m *pm2Manager) Start() error {
+	const op string = "process.pm2Manager.Start"
+	for _, processes := range m.pool {
+		for _, proc := range processes {
+			if err := m.start(proc); err != nil {
+				return xerror.New(op, err)
+			}
+		}
+	}
+	return nil
+}
+
+func (m *pm2Manager) start(p Process) error {
+	const op string = "process.pm2Manager.start"
+	resolver := func() error {
+		// first, we try to start the process.
+		if err := m.run(startCommand, p); err != nil {
+			return err
+		}
+		// we wait the process to be ready.
+		m.warmup(p)
+		// if the process failed to start correctly,
+		// we have to restart it.
+		if !m.IsViable(p) && maximumRestartAttempts > 0 {
+			return m.Restart(p)
+		}
+		// the process is viable, let's log its
+		// output.
+		return m.logs(p)
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (m *pm2Manager) List() List {
+	m.listLock.Lock()
+	defer m.listLock.Unlock()
+	return m.list.toList()
+}
+
+func (m *pm2Manager) All() []Process {
+	var result []Process
+	for _, processes := range m.pool {
+		result = append(result, processes...)
+	}
+	return result
+}
+
+func (m *pm2Manager) Processes(key Key) []Process {
+	return m.pool[key]
+}
+
+func (m *pm2Manager) Restart(p Process) error {
+	const op string = "process.pm2Manager.Restart"
+	resolver := func() error {
+		var attempts uint
+		for attempts < maximumRestartAttempts {
+			// we restart the process.
+			if err := m.run(restartCommand, p); err != nil {
+				return err
+			}
+			// we wait the process to be ready.
+			m.warmup(p)
+			attempts++
+			// if the process is viable, we
+			// leave.
+			if m.IsViable(p) {
+				return m.logs(p)
+			}
+		}
+		return fmt.Errorf("failed to start '%s'", p.ID())
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (m *pm2Manager) Stop(p Process) error {
+	const op string = "process.pm2Manager.Stop"
+	if err := m.run(stopCommand, p); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (m *pm2Manager) IsViable(p Process) bool {
+	if !p.viabilityFunc()(m.logger) {
+		return false
+	}
+	m.listLock.Lock()
+	defer m.listLock.Unlock()
+	return m.list.isOnline(p)
+}
+
+func (m *pm2Manager) Memory(p Process) (int64, error) {
+	const op string = "process.pm2Manager.Memory"
+	m.listLock.Lock()
+	defer m.listLock.Unlock()
+	memory, err := m.list.memory(p)
+	if err != nil {
+		return 0, xerror.New(op, err)
+	}
+	return memory, nil
+}
+
+func (m *pm2Manager) warmup(p Process) {
+	const op string = "process.pm2Manager.warmup"
+	warmupTime := p.warmupTime()
+	m.logger.DebugfOp(
+		op,
+		"waiting '%v' for allowing '%s' to warmup",
+		warmupTime,
+		p.ID(),
+	)
+	time.Sleep(warmupTime)
+}
+
+func (m *pm2Manager) logs(p Process) error {
+	const op string = "process.pm2Manager.logs"
+	if m.config.LogLevel() == xlog.DebugLevel {
+		if err := m.run(logsCommand, p); err != nil {
+			return xerror.New(op, err)
+		}
+	}
+	return nil
+}
+
+func (m *pm2Manager) run(pm2Cmd command, p Process) error {
+	const op string = "process.pm2Manager.run"
+	resolver := func() error {
+		args := []string{
+			string(pm2Cmd),
+			p.binary(),
+		}
+		if pm2Cmd == startCommand {
+			args = append(args, fmt.Sprintf("--name=%s", p.ID()))
+			args = append(args, "--interpreter=none", "--")
+			args = append(args, p.args()...)
+		}
+		cmd, err := xexec.Command(m.logger, "pm2", args...)
+		if err != nil {
+			return err
+		}
+		xexec.LogBeforeExecute(m.logger, cmd)
+		return cmd.Start()
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Manager(new(pm2Manager))
+)
--- a/internal/pkg/process/process.go
+++ b/internal/pkg/process/process.go
@@ -0,0 +1,40 @@
+package process
+
+import (
+	"time"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+)
+
+type Process interface {
+	ID() string
+	Host() string
+	Port() int
+	binary() string
+	args() []string
+	warmupTime() time.Duration
+	viabilityFunc() func(logger xlog.Logger) bool
+}
+
+type ListItem struct {
+	Name    string  `json:"name"`
+	Status  string  `json:"status"`
+	Restart int64   `json:"restart"`
+	Memory  int64   `json:"memory"`
+	CPU     float64 `json:"cpu"`
+}
+
+type List []ListItem
+
+type Key string
+
+type Manager interface {
+	Start() error
+	List() List
+	All() []Process
+	Processes(key Key) []Process
+	Restart(proc Process) error
+	Stop(proc Process) error
+	IsViable(proc Process) bool
+	Memory(proc Process) (int64, error)
+}
--- a/internal/pkg/process/soffice.go
+++ b/internal/pkg/process/soffice.go
@@ -0,0 +1,74 @@
+package process
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+)
+
+const SofficeKey Key = "soffice"
+
+type sofficeProcess struct {
+	id   string
+	host string
+	port int
+}
+
+// NewSofficeProcess returns a LibreOffice
+// headless process.
+func NewSofficeProcess(id, host string, port int) Process {
+	return sofficeProcess{
+		id:   id,
+		host: host,
+		port: port,
+	}
+}
+
+func (p sofficeProcess) ID() string {
+	return p.id
+}
+
+func (p sofficeProcess) Host() string {
+	return p.host
+}
+
+func (p sofficeProcess) Port() int {
+	return p.port
+}
+
+func (p sofficeProcess) binary() string {
+	return "soffice"
+}
+
+func (p sofficeProcess) args() []string {
+	return []string{
+		// see https://ask.libreoffice.org/en/question/42975/how-can-i-run-multiple-instances-of-sofficebin-at-a-time/.
+		fmt.Sprintf("-env:UserInstallation=file:///tmp/%d", p.port),
+		"--headless",
+		"--invisible",
+		"--nocrashreport",
+		"--nodefault",
+		"--nofirststartwizard",
+		"--nologo",
+		"--norestore",
+		fmt.Sprintf("--accept=socket,host=%s,port=%d,tcpNoDelay=1;urp;StarOffice.ComponentContext", p.host, p.port),
+	}
+}
+
+func (p sofficeProcess) warmupTime() time.Duration {
+	return 3 * time.Second
+}
+
+func (p sofficeProcess) viabilityFunc() func(logger xlog.Logger) bool {
+	const op string = "process.sofficeProcess.viabilityFunc"
+	return func(logger xlog.Logger) bool {
+		// TODO find a way to check.
+		return true
+	}
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Process(new(sofficeProcess))
+)
--- a/internal/pkg/xerrgroup/doc.go
+++ b/internal/pkg/xerrgroup/doc.go
@@ -0,0 +1,6 @@
+/*
+Package xerrgroup helps running
+many functions simultaneously and wait until
+execution has completed or an error is encountered.
+*/
+package xerrgroup
--- a/internal/pkg/xerrgroup/xerrgroup.go
+++ b/internal/pkg/xerrgroup/xerrgroup.go
@@ -0,0 +1,20 @@
+package xerrgroup
+
+import (
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+	"golang.org/x/sync/errgroup"
+)
+
+// Run runs all functions simultaneously and wait until
+// execution has completed or an error is encountered.
+func Run(fn ...func() error) error {
+	const op string = "xerrgroup.Run"
+	eg := errgroup.Group{}
+	for _, f := range fn {
+		eg.Go(f)
+	}
+	if err := eg.Wait(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
--- a/loadtesting/README.md
+++ b/loadtesting/README.md
@@ -0,0 +1,113 @@
+# Load testing
+
+You may wonder how Gotenberg behaves under load.
+
+In order to help you having an idea, we created a bunch of scenarios for the
+[k6](https://docs.k6.io/docs) load testing tool.
+
+The Gotenberg container (version `6.0.0` and default options) was hosted on a AWS EC2 `t2.micro` instance (1 vCPU and 1 Go of RAM, low to average network performances).
+
+The k6 scenarios have been performed on a MacBook Pro 2016 (2 GHz Intel Core i5 and 16 Go 1867 MHz LPDDR3).
+
+## HTML
+
+The HTML scenario is quite simple:
+
+* Ramp up from 0 to 100 virtual users, each one uploading as many time as possible the [HTML test data](../test/testdata/html).
+* Stop when at least one response is not an HTTP 200 code.
+
+```bash
+$ k6 run --env MAX_VUS=100 --env BASE_URL=http://ec2-foo.eu-west-1.compute.amazonaws.com html.js
+
+          /\      |‾‾|  /‾‾/  /‾/   
+     /\  /  \     |  |_/  /  / /    
+    /  \/    \    |      |  /  ‾‾\  
+   /          \   |  |‾\  \ | (_) | 
+  / __________ \  |__|  \__\ \___/ .io
+
+  execution: local
+     output: -
+     script: html.js
+
+    duration: -,  iterations: -
+         vus: 1, max: 100
+
+    done [==========================================================] 1m11.9s / 10m0s
+
+    ✗ is status 200
+     ↳  99% — ✓ 179 / ✗ 1
+    ✗ is not status 504
+     ↳  99% — ✓ 179 / ✗ 1
+    ✓ is not status 500
+
+    checks.....................: 99.62% ✓ 538   ✗ 2    
+    data_received..............: 41 MB  576 kB/s
+    data_sent..................: 8.5 MB 118 kB/s
+  ✗ failed requests............: 1      0.013895/s
+    http_req_blocked...........: avg=1.58ms   min=2µs   med=5µs    max=59.73ms  p(90)=10.19µs  p(95)=20.57ms 
+    http_req_connecting........: avg=1.56ms   min=0s    med=0s     max=59.61ms  p(90)=0s       p(95)=20.48ms 
+    http_req_duration..........: avg=2.3s     min=1.32s med=1.67s  max=10.2s    p(90)=4.41s    p(95)=7.54s   
+    http_req_receiving.........: avg=99.01ms  min=127µs med=98.4ms max=154.86ms p(90)=115.92ms p(95)=122.42ms
+    http_req_sending...........: avg=232.69µs min=133µs med=207µs  max=1.16ms   p(90)=335.4µs  p(95)=382.64µs
+    http_req_tls_handshaking...: avg=0s       min=0s    med=0s     max=0s       p(90)=0s       p(95)=0s      
+    http_req_waiting...........: avg=2.2s     min=1.21s med=1.56s  max=10.2s    p(90)=4.32s    p(95)=7.45s   
+    http_reqs..................: 180    2.501138/s
+    iteration_duration.........: avg=2.3s     min=1.33s med=1.67s  max=10.22s   p(90)=4.45s    p(95)=7.54s   
+    iterations.................: 180    2.501138/s
+    vus........................: 12     min=1   max=12 
+    vus_max....................: 100    min=100 max=100
+```
+
+In our use case, when reaching 12 virtual users (~2,5 requests per second), some incoming requests cannot be fulfilled before 10 seconds (`DEFAULT_WAIT_TIMEOUT` value).
+During this test, CPU usage went from 0 to 100% and memory usage stayed low (Google Chrome go from 64.1 MB to 64.9 MB).
+
+## Office
+
+The Office scenario is the same as the HTML scenario, but with a [document.docx](../test/testdata/office/document.docx).
+
+```bash
+$ k6 run --env MAX_VUS=100 --env BASE_URL=http://ec2-foo.eu-west-1.compute.amazonaws.com office.js
+
+          /\      |‾‾|  /‾‾/  /‾/   
+     /\  /  \     |  |_/  /  / /    
+    /  \/    \    |      |  /  ‾‾\  
+   /          \   |  |‾\  \ | (_) | 
+  / __________ \  |__|  \__\ \___/ .io
+
+  execution: local
+     output: -
+     script: office.js
+
+    duration: -,  iterations: -
+         vus: 1, max: 100
+
+    done [==========================================================] 2m7.9s / 10m0s
+
+    ✗ is status 200
+     ↳  99% — ✓ 481 / ✗ 3
+    ✗ is not status 504
+     ↳  99% — ✓ 481 / ✗ 3
+    ✓ is not status 500
+
+    checks.....................: 99.58% ✓ 1446  ✗ 6    
+    data_received..............: 40 MB  312 kB/s
+    data_sent..................: 45 MB  348 kB/s
+  ✗ failed requests............: 3      0.023446/s
+    http_req_blocked...........: avg=1.85ms   min=2µs      med=5µs     max=373.57ms p(90)=12.69µs p(95)=23.84µs
+    http_req_connecting........: avg=1.11ms   min=0s       med=0s      max=47.62ms  p(90)=0s      p(95)=0s     
+    http_req_duration..........: avg=2.65s    min=289.89ms med=2.48s   max=10.08s   p(90)=4.51s   p(95)=5.43s  
+    http_req_receiving.........: avg=57.15ms  min=79µs     med=51.53ms max=200.89ms p(90)=81.12ms p(95)=91.61ms
+    http_req_sending...........: avg=387.86µs min=159µs    med=332µs   max=3.87ms   p(90)=513.1µs p(95)=695µs  
+    http_req_tls_handshaking...: avg=0s       min=0s       med=0s      max=0s       p(90)=0s      p(95)=0s     
+    http_req_waiting...........: avg=2.59s    min=264.48ms med=2.4s    max=10.08s   p(90)=4.45s   p(95)=5.37s  
+    http_reqs..................: 484    3.782635/s
+    iteration_duration.........: avg=2.65s    min=290.24ms med=2.48s   max=10.08s   p(90)=4.51s   p(95)=5.43s  
+    iterations.................: 484    3.782635/s
+    vus........................: 22     min=1   max=22 
+    vus_max....................: 100    min=100 max=100
+```
+
+In our use case, when reaching 22 virtual users (~3,7 requests per second), some incoming requests cannot be fulfilled before 10 seconds (`DEFAULT_WAIT_TIMEOUT` value).
+During this test, CPU usage went from 0 to 100% and memory usage stayed low.
+
+## Merge
--- a/loadtesting/html.js
+++ b/loadtesting/html.js
@@ -0,0 +1,44 @@
+import http from "k6/http";
+import { Counter } from "k6/metrics";
+import { check } from "k6";
+
+let indexFile = open("../test/testdata/html/index.html", "b"),
+    styleFile = open("../test/testdata/html/style.css", "b"),
+    headerFile = open("../test/testdata/html/header.html", "b"),
+    footerFile = open("../test/testdata/html/footer.html", "b"),
+    fontFile = open("../test/testdata/html/font.woff", "b"),
+    imgFile = open("../test/testdata/html/img.gif", "b");
+
+let failCounter = new Counter("failed requests");
+
+export let options = {
+  stages: [
+    { duration: "10m", target: __ENV.MAX_VUS }
+  ],
+  thresholds: {
+    "failed requests": [{
+      threshold: "count<1", 
+      abortOnFail: true,
+    }]
+  }
+}
+
+export default function() {
+  let data = {
+    "index.html": http.file(indexFile, "index.html"),
+    "style.css": http.file(styleFile, "style.css"),
+    "header.html": http.file(headerFile, "header.html"),
+    "footer.html": http.file(footerFile, "footer.html"),
+    "font.woff": http.file(fontFile, "font.woff"),
+    "img.gif": http.file(imgFile, "img.gif")
+  }
+  let res = http.post(__ENV.BASE_URL + '/convert/html', data);
+  check(res, {
+    "is status 200": (r) => r.status === 200,
+    "is not status 504": (r) => r.status !== 504,
+    "is not status 500": (r) => r.status !== 500
+  });
+  if (res.status !== 200) {
+    failCounter.add(1);
+  }
+}
--- a/loadtesting/merge.js
+++ b/loadtesting/merge.js
@@ -0,0 +1,18 @@
+import http from "k6/http";
+import { check } from "k6";
+
+let pdf1File = open("../test/testdata/pdf/gotenberg.pdf", "b"),
+    pdf2File = open("../test/testdata/pdf/gotenberg_bis.pdf", "b");
+
+export default function() {
+  var data = {
+      "gotenberg.pdf": http.file(pdf1File, "gotenberg.pdf"),
+      "gotenberg_bis.pdf": http.file(pdf2File, "gotenberg_bis.pdf")
+  }
+  var res = http.post(__ENV.BASE_URL + '/merge', data);
+  check(res, {
+    "is status 200": (r) => r.status === 200,
+    "is not status 504": (r) => r.status !== 504,
+    "is not status 500": (r) => r.status !== 500,
+  });
+}
--- a/loadtesting/office.js
+++ b/loadtesting/office.js
@@ -0,0 +1,34 @@
+import http from "k6/http";
+import { Counter } from "k6/metrics";
+import { check } from "k6";
+
+let documentFile = open("../test/testdata/office/document.docx", "b");
+
+let failCounter = new Counter("failed requests");
+
+export let options = {
+  stages: [
+    { duration: "10m", target: __ENV.MAX_VUS }
+  ],
+  thresholds: {
+    "failed requests": [{
+      threshold: "count<1", 
+      abortOnFail: true,
+    }]
+  }
+}
+
+export default function() {
+  let data = {
+      "document.docx": http.file(documentFile, "document.docx")
+  }
+  let res = http.post(__ENV.BASE_URL + '/convert/office', data);
+  check(res, {
+    "is status 200": (r) => r.status === 200,
+    "is not status 504": (r) => r.status !== 504,
+    "is not status 500": (r) => r.status !== 500,
+  });
+  if (res.status !== 200) {
+    failCounter.add(1);
+  }
+}