process balancing: better implementation (wip)

cmd/gotenberg/main.go

@@ -9,7 +9,6 @@ import (
 	"github.com/thecodingmachine/gotenberg/internal/app/xhttp"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
 	"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"
 )
@@ -27,30 +26,18 @@ func main() {
 	}
 	systemLogger.InfofOp(op, "Gotenberg %s", version)
 	systemLogger.DebugfOp(op, "configuration: %+v", config)
-	// create PM2 manager and start processes.
-	manager := process.NewPM2Manager(systemLogger, config)
-	if err := manager.Start(); err != nil {
+	// create our prinery.
+	prinry, err := prinery.NewPM2Prinery(systemLogger, config)
+	if err != nil {
 		systemLogger.FatalOp(op, err)
 	}
-	// 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()
+	// TODO use chan
+	// TODO stop prinery
+	if err = prinry.Start(make(chan error, 1)); err != nil {
+		systemLogger.FatalOp(op, err)
 	}
 	// create our API.
-	srv := xhttp.New(config, manager, chromePrinery, sofficePrinery)
+	srv := xhttp.New(config, prinry)
 	// 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())

internal/app/xhttp/handler.go

@@ -1,6 +1,7 @@
 package xhttp
 
 import (
+	timeoutContext "context"
 	"fmt"
 	"net/http"
 	"os"
@@ -9,8 +10,6 @@ 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/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"
@@ -72,8 +71,11 @@ func mergeHandler(c echo.Context) error {
 		if err != nil {
 			return err
 		}
-		p := print.NewMergePrint(logger, fpaths)
-		return convert(ctx, nil, p, timeout)
+		prinry := ctx.Prinery()
+		printFunc := func(ctx timeoutContext.Context, logger xlog.Logger, dest string) error {
+			return prinry.Merge(ctx, logger, dest, fpaths)
+		}
+		return convert(ctx, timeout, printFunc)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -87,7 +89,6 @@ 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()
@@ -104,8 +105,11 @@ func htmlHandler(c echo.Context) error {
 		if err != nil {
 			return err
 		}
-		p := print.NewHTMLPrint(logger, fpath, opts)
-		return convert(ctx, prinry, p, timeout)
+		prinry := ctx.Prinery()
+		printFunc := func(ctx timeoutContext.Context, logger xlog.Logger, dest string) error {
+			return prinry.HTML(ctx, logger, dest, fpath, opts)
+		}
+		return convert(ctx, timeout, printFunc)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -119,7 +123,6 @@ 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()
@@ -143,8 +146,11 @@ func urlHandler(c echo.Context) error {
 		if err != nil {
 			return err
 		}
-		p := print.NewURLPrint(logger, remoteURL, opts)
-		return convert(ctx, prinry, p, timeout)
+		prinry := ctx.Prinery()
+		printFunc := func(ctx timeoutContext.Context, logger xlog.Logger, dest string) error {
+			return prinry.URL(ctx, logger, dest, remoteURL, opts)
+		}
+		return convert(ctx, timeout, printFunc)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -158,7 +164,6 @@ 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()
@@ -175,11 +180,11 @@ func markdownHandler(c echo.Context) error {
 		if err != nil {
 			return err
 		}
-		p, err := print.NewMarkdownPrint(logger, fpath, opts)
-		if err != nil {
-			return err
+		prinry := ctx.Prinery()
+		printFunc := func(ctx timeoutContext.Context, logger xlog.Logger, dest string) error {
+			return prinry.Markdown(ctx, logger, dest, fpath, opts)
 		}
-		return convert(ctx, prinry, p, timeout)
+		return convert(ctx, timeout, printFunc)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -193,7 +198,6 @@ 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()
@@ -202,7 +206,7 @@ func officeHandler(c echo.Context) error {
 		if err != nil {
 			return err
 		}
-		opts, err := officePrintOptions(r, config)
+		opts, err := unoconvPrintOptions(r, config)
 		if err != nil {
 			return err
 		}
@@ -223,8 +227,11 @@ func officeHandler(c echo.Context) error {
 		if err != nil {
 			return err
 		}
-		p := print.NewOfficePrint(logger, fpaths, opts)
-		return convert(ctx, prinry, p, timeout)
+		prinry := ctx.Prinery()
+		printFunc := func(ctx timeoutContext.Context, logger xlog.Logger, dest string) error {
+			return prinry.Office(ctx, logger, dest, fpaths, opts)
+		}
+		return convert(ctx, timeout, printFunc)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -232,7 +239,11 @@ func officeHandler(c echo.Context) error {
 	return nil
 }
 
-func convert(ctx context.Context, prinry *prinery.Prinery, prnt print.Print, timeout float64) error {
+func convert(
+	ctx context.Context,
+	timeout float64,
+	printFunc func(ctx timeoutContext.Context, logger xlog.Logger, dest string) error,
+) error {
 	const op string = "xhttp.convert"
 	resolver := func() error {
 		logger := ctx.XLogger()
@@ -245,13 +256,13 @@ func convert(ctx context.Context, prinry *prinery.Prinery, prnt print.Print, tim
 		// or an error.
 		if !r.HasArg(resource.WebhookURLArgKey) {
 			logger.DebugfOp(op, "no '%s' found, converting synchronously", resource.WebhookURLArgKey)
-			return convertSync(ctx, prinry, prnt, timeout, filename, fpath)
+			return convertSync(ctx, timeout, filename, fpath, printFunc)
 		}
 		// 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, prinry, prnt, timeout, filename, fpath)
+		return convertAsync(ctx, timeout, filename, fpath, printFunc)
 	}
 	if err := resolver(); err != nil {
 		return xerror.New(op, err)
@@ -259,19 +270,19 @@ func convert(ctx context.Context, prinry *prinery.Prinery, prnt print.Print, tim
 	return nil
 }
 
-func convertSync(ctx context.Context, prinry *prinery.Prinery, prnt print.Print, timeout float64, filename, fpath string) error {
+func convertSync(
+	ctx context.Context,
+	timeout float64,
+	filename, dest string,
+	printFunc func(ctx timeoutContext.Context, logger xlog.Logger, dest string) error,
+) error {
 	const op = "xhttp.convertSync"
 	logger := ctx.XLogger()
 	r := ctx.MustResource()
 	timeoutCtx, cancel := xcontext.WithTimeout(logger, timeout)
 	defer cancel()
 	resolver := func() error {
-		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 {
+		if err := printFunc(timeoutCtx, logger, dest); err != nil {
 			return err
 		}
 		if !r.HasArg(resource.ResultFilenameArgKey) {
@@ -281,7 +292,7 @@ func convertSync(ctx context.Context, prinry *prinery.Prinery, prnt print.Print,
 				resource.RemoteURLArgKey,
 				filename,
 			)
-			if err := ctx.Attachment(fpath, filename); err != nil {
+			if err := ctx.Attachment(dest, filename); err != nil {
 				return err
 			}
 			return nil
@@ -295,7 +306,7 @@ func convertSync(ctx context.Context, prinry *prinery.Prinery, prnt print.Print,
 		if err != nil {
 			return err
 		}
-		if err := ctx.Attachment(fpath, filename); err != nil {
+		if err := ctx.Attachment(dest, filename); err != nil {
 			return err
 		}
 		return nil
@@ -309,7 +320,12 @@ func convertSync(ctx context.Context, prinry *prinery.Prinery, prnt print.Print,
 	return nil
 }
 
-func convertAsync(ctx context.Context, prinry *prinery.Prinery, prnt print.Print, timeout float64, filename, fpath string) error {
+func convertAsync(
+	ctx context.Context,
+	timeout float64,
+	filename, dest string,
+	printFunc func(ctx timeoutContext.Context, logger xlog.Logger, dest string) error,
+) error {
 	const op = "xhttp.convertAsync"
 	logger := ctx.XLogger()
 	r := ctx.MustResource()
@@ -325,19 +341,12 @@ func convertAsync(ctx context.Context, prinry *prinery.Prinery, prnt print.Print
 		defer r.Close() // nolint: errcheck
 		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 {
+		if err := printFunc(timeoutCtx, logger, dest); err != nil {
 			xerr := xerror.New(op, err)
 			logger.ErrorOp(xerror.Op(xerr), xerr)
 			return
 		}
-		f, err := os.Open(fpath)
+		f, err := os.Open(dest)
 		if err != nil {
 			xerr := xerror.New(op, err)
 			logger.ErrorOp(xerror.Op(xerr), xerr)

internal/app/xhttp/middleware.go

@@ -8,7 +8,6 @@ import (
 	"github.com/thecodingmachine/gotenberg/internal/app/xhttp/pkg/resource"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
 	"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"
@@ -16,12 +15,7 @@ import (
 
 // contextMiddleware extends the default echo.Context with
 // our custom context.Context.
-func contextMiddleware(
-	config conf.Config,
-	manager process.Manager,
-	chromePrinery *prinery.Prinery,
-	sofficePrinery *prinery.Prinery,
-) echo.MiddlewareFunc {
+func contextMiddleware(config conf.Config, prinry prinery.Prinery) echo.MiddlewareFunc {
 	return func(next echo.HandlerFunc) echo.HandlerFunc {
 		return func(c echo.Context) error {
 			// generate a unique identifier for the request.
@@ -31,7 +25,7 @@ func contextMiddleware(
 			logger := xlog.New(config.LogLevel(), trace)
 			// extend the current echo context with our custom
 			// context.
-			ctx := context.New(c, logger, config, manager, chromePrinery, sofficePrinery)
+			ctx := context.New(c, logger, config, prinry)
 			// if its an healthcheck request, there
 			// is no need to create a Resource.
 			if ctx.Path() == pingEndpoint {

internal/app/xhttp/option.go

@@ -3,37 +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/print"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/prinery"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
 )
 
-func chromePrintOptions(r resource.Resource, config conf.Config) (print.ChromePrintOptions, error) {
+func chromePrintOptions(r resource.Resource, config conf.Config) (prinery.ChromePrintOptions, error) {
 	const op string = "xhttp.chromePrintOptions"
-	resolver := func() (print.ChromePrintOptions, error) {
+	resolver := func() (prinery.ChromePrintOptions, error) {
 		waitDelay, err := resource.WaitDelayArg(r, config)
 		if err != nil {
-			return print.ChromePrintOptions{}, err
+			return prinery.ChromePrintOptions{}, err
 		}
 		headerHTML, footerHTML,
 			err := resource.HeaderFooterContents(r, config)
 		if err != nil {
-			return print.ChromePrintOptions{}, err
+			return prinery.ChromePrintOptions{}, err
 		}
 		paperWidth, paperHeight,
 			err := resource.PaperSizeArgs(r, config)
 		if err != nil {
-			return print.ChromePrintOptions{}, err
+			return prinery.ChromePrintOptions{}, err
 		}
 		marginTop, marginBottom, marginLeft, marginRight,
 			err := resource.MarginArgs(r, config)
 		if err != nil {
-			return print.ChromePrintOptions{}, err
+			return prinery.ChromePrintOptions{}, err
 		}
 		landscape, err := r.BoolArg(resource.LandscapeArgKey, false)
 		if err != nil {
-			return print.ChromePrintOptions{}, err
+			return prinery.ChromePrintOptions{}, err
 		}
-		return print.ChromePrintOptions{
+		return prinery.ChromePrintOptions{
 			WaitDelay:    waitDelay,
 			HeaderHTML:   headerHTML,
 			FooterHTML:   footerHTML,
@@ -53,14 +53,14 @@ func chromePrintOptions(r resource.Resource, config conf.Config) (print.ChromePr
 	return opts, nil
 }
 
-func officePrintOptions(r resource.Resource, config conf.Config) (print.OfficePrintOptions, error) {
-	const op string = "xhttp.officePrintOptions"
-	resolver := func() (print.OfficePrintOptions, error) {
+func unoconvPrintOptions(r resource.Resource, config conf.Config) (prinery.UnoconvPrintOptions, error) {
+	const op string = "xhttp.unoconvPrintOptions"
+	resolver := func() (prinery.UnoconvPrintOptions, error) {
 		landscape, err := r.BoolArg(resource.LandscapeArgKey, false)
 		if err != nil {
-			return print.OfficePrintOptions{}, err
+			return prinery.UnoconvPrintOptions{}, err
 		}
-		return print.OfficePrintOptions{
+		return prinery.UnoconvPrintOptions{
 			Landscape: landscape,
 		}, nil
 	}

internal/app/xhttp/pkg/context/context.go

@@ -14,7 +14,6 @@ import (
 	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/normalize"
 	"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"
 )
@@ -22,13 +21,11 @@ import (
 // Context extends the default echo.Context.
 type Context struct {
 	echo.Context
-	logger         xlog.Logger
-	config         conf.Config
-	manager        process.Manager
-	chromePrinery  *prinery.Prinery
-	sofficePrinery *prinery.Prinery
-	resource       resource.Resource
-	startTime      time.Time
+	logger    xlog.Logger
+	config    conf.Config
+	prinry    prinery.Prinery
+	resource  resource.Resource
+	startTime time.Time
 }
 
 // New creates a new Context.
@@ -36,17 +33,13 @@ func New(
 	c echo.Context,
 	logger xlog.Logger,
 	config conf.Config,
-	manager process.Manager,
-	chromePrinery *prinery.Prinery,
-	sofficePrinery *prinery.Prinery,
+	prinry prinery.Prinery,
 ) Context {
 	return Context{
 		c,
 		logger,
 		config,
-		manager,
-		chromePrinery,
-		sofficePrinery,
+		prinry,
 		resource.Resource{},
 		time.Now(),
 	}
@@ -89,7 +82,8 @@ func (ctx Context) Config() conf.Config {
 // one of the processes is not viable.
 func (ctx Context) ProcessesHealthcheck() error {
 	const op string = "context.Context.ProcessesHealthcheck"
-	processes := ctx.manager.All()
+	// TODO
+	/*processes := ctx.manager.All()
 	for _, p := range processes {
 		if !ctx.manager.IsViable(p) {
 			return xerror.New(
@@ -97,42 +91,14 @@ func (ctx Context) ProcessesHealthcheck() error {
 				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
+// Prinery returns the instance of prinery.Prinery
+// associated with the Context.
+func (ctx Context) Prinery() prinery.Prinery {
+	return ctx.prinry
 }
 
 // WithResource creates a resource.Resource and

internal/app/xhttp/xhttp.go

@@ -4,20 +4,14 @@ import (
 	"github.com/labstack/echo/v4"
 	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
 	"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,
-	manager process.Manager,
-	chromePrinery *prinery.Prinery,
-	sofficePrinery *prinery.Prinery,
-) *echo.Echo {
+func New(config conf.Config, prinry prinery.Prinery) *echo.Echo {
 	srv := echo.New()
 	srv.HideBanner = true
 	srv.HidePort = true
-	srv.Use(contextMiddleware(config, manager, chromePrinery, sofficePrinery))
+	srv.Use(contextMiddleware(config, prinry))
 	srv.Use(loggerMiddleware())
 	srv.Use(cleanupMiddleware())
 	srv.Use(errorMiddleware())

internal/pkg/conf/conf.go

@@ -201,6 +201,16 @@ func (c Config) DefaultListenPort() int64 {
 	return c.defaultListenPort
 }
 
+func (c Config) GoogleChromeInstances() int64 {
+	// TODO: replace DisableGoogleChrome
+	return 2
+}
+
+func (c Config) SofficeInstances() int64 {
+	// TODO: replace DisableUnoconv
+	return 2
+}
+
 /*
 DisableGoogleChrome returns true if
 Google Chrome is disabled in the

internal/pkg/prinery/chrome.go

@@ -0,0 +1,327 @@
+package prinery
+
+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/xerrgroup"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xtime"
+)
+
+type chromeProcess struct {
+	devtPort uint
+}
+
+func newChromeProcesses(nInstances int64) []process {
+	processes := make([]process, nInstances)
+	var i int64
+	var currentPort uint = 9222
+	for i = 0; i < nInstances; i++ {
+		processes[i] = chromeProcess{
+			devtPort: currentPort,
+		}
+		currentPort++
+	}
+	return processes
+}
+
+func (p chromeProcess) id() string {
+	return fmt.Sprintf("%s-%d", p.binary(), p.port())
+}
+
+func (p chromeProcess) host() string {
+	return "127.0.0.1"
+}
+
+func (p chromeProcess) port() uint {
+	return p.devtPort
+}
+
+func (p chromeProcess) spec() processSpec {
+	return p
+}
+
+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 = "prinery.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
+	}
+}
+
+type chromePrinter struct {
+	logger xlog.Logger
+	url    string
+	opts   ChromePrintOptions
+}
+
+func (p chromePrinter) print(ctx context.Context, spec processSpec, dest string) error {
+	const op string = "prinery.chromePrinter.print"
+	resolver := func() error {
+		devtEndpoint := fmt.Sprintf("http://%s:%d", spec.host(), spec.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", spec.host(), spec.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 chromePrinter) enableEvents(ctx context.Context, client *cdp.Client) error {
+	const op string = "prinery.chromePrinter.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 chromePrinter) listenEvents(ctx context.Context, client *cdp.Client) error {
+	const op string = "prinery.chromePrinter.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 (
+	_ = processSpec(new(chromeProcess))
+	_ = process(new(chromeProcess))
+	_ = printer(new(chromePrinter))
+)

internal/pkg/prinery/markdown.go

@@ -0,0 +1,68 @@
+package prinery
+
+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"
+)
+
+func newMarkdownPrinter(logger xlog.Logger, fpath string, opts ChromePrintOptions) (printer, error) {
+	const op string = "prinery.newMarkdownPrinter"
+	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 nil, xerror.New(op, err)
+	}
+	return chromePrinter{
+		logger: logger,
+		url:    URL,
+		opts:   opts,
+	}, nil
+}
+
+type templateData struct {
+	DirPath string
+}
+
+func markdownToHTML(dirPath, filename string) (template.HTML, error) {
+	const op string = "prinery.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
+}

internal/pkg/prinery/merge.go

@@ -0,0 +1,39 @@
+package prinery
+
+import (
+	"context"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xexec"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+)
+
+type mergePrinter struct {
+	logger xlog.Logger
+	fpaths []string
+}
+
+func (p mergePrinter) print(ctx context.Context, spec processSpec, dest string) error {
+	const op string = "prinery.mergePrinter.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
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = printer(new(mergePrinter))
+)

internal/pkg/prinery/pm2.go

@@ -0,0 +1,365 @@
+package prinery
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"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"
+)
+
+type command string
+
+const (
+	startCommand   command = "start"
+	restartCommand command = "restart"
+	stopCommand    command = "stop"
+	logsCommand    command = "logs"
+	jlistCommand   command = "jlist"
+)
+
+const maximumRestartAttempts uint = 3
+
+type pm2 struct {
+	logger      xlog.Logger
+	config      conf.Config
+	chromeUnit  *unit
+	sofficeUnit *unit
+	processes   []process
+}
+
+func NewPM2Prinery(logger xlog.Logger, config conf.Config) (Prinery, error) {
+	const op string = "prinery.NewPM2Prinery"
+	resolver := func() (*pm2, error) {
+		m := &pm2{
+			logger: logger,
+			config: config,
+		}
+		chromeProcesses := newChromeProcesses(config.GoogleChromeInstances())
+		if len(chromeProcesses) > 0 {
+			unit, err := newUnit(logger, processesToSpecs(chromeProcesses))
+			if err != nil {
+				return nil, err
+			}
+			m.chromeUnit = unit
+		}
+		sofficeProcesses := newSofficesProcesses(config.SofficeInstances())
+		if len(sofficeProcesses) > 0 {
+			unit, err := newUnit(logger, processesToSpecs(sofficeProcesses))
+			if err != nil {
+				return nil, err
+			}
+			m.sofficeUnit = unit
+		}
+		m.processes = append(chromeProcesses, sofficeProcesses...)
+		return m, nil
+	}
+	p, err := resolver()
+	if err != nil {
+		return nil, xerror.New(op, err)
+	}
+	return p, nil
+}
+
+func (m *pm2) Start(emergency chan error) error {
+	const op string = "prinery.pm2.Start"
+	// start processes.
+	// those lines "works" but processes
+	// fail to start...
+	/*var wg sync.WaitGroup
+	result := make(chan error, len(m.processes))
+	for _, proc := range m.processes {
+		wg.Add(1)
+		go func(proc process, result chan error) {
+			result <- m.start(proc)
+			wg.Done()
+		}(proc, result)
+	}
+	wg.Wait()
+	close(result)
+	for err := range result {
+		if err != nil {
+			return xerror.New(op, err)
+		}
+	}*/
+	for _, proc := range m.processes {
+		if err := m.start(proc); err != nil {
+			return xerror.New(op, err)
+		}
+	}
+	// start units.
+	if m.chromeUnit != nil {
+		go m.chromeUnit.start(emergency)
+	}
+	if m.sofficeUnit != nil {
+		go m.sofficeUnit.start(emergency)
+	}
+	return nil
+}
+
+func (m *pm2) HTML(
+	ctx context.Context,
+	logger xlog.Logger,
+	dest, fpath string,
+	opts ChromePrintOptions,
+) error {
+	const op string = "prinery.pm2.HTML"
+	resolver := func() error {
+		if m.chromeUnit == nil {
+			return errors.New("cannot handle HTML print request as there is no chromeUnit")
+		}
+		URL := fmt.Sprintf("file://%s", fpath)
+		p := chromePrinter{
+			logger: logger,
+			url:    URL,
+			opts:   opts,
+		}
+		req := request{
+			ctx:     ctx,
+			logger:  logger,
+			printer: p,
+			dest:    dest,
+			result:  make(chan error),
+		}
+		m.chromeUnit.dispatch(req)
+		err := <-req.result
+		return err
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (m *pm2) URL(
+	ctx context.Context,
+	logger xlog.Logger, dest, URL string,
+	opts ChromePrintOptions,
+) error {
+	const op string = "prinery.pm2.URL"
+	resolver := func() error {
+		if m.chromeUnit == nil {
+			return errors.New("cannot handle URL print request as there is no chromeUnit")
+		}
+		p := chromePrinter{
+			logger: logger,
+			url:    URL,
+			opts:   opts,
+		}
+		req := request{
+			ctx:     ctx,
+			logger:  logger,
+			printer: p,
+			dest:    dest,
+			result:  make(chan error),
+		}
+		m.chromeUnit.dispatch(req)
+		err := <-req.result
+		return err
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (m *pm2) Markdown(
+	ctx context.Context,
+	logger xlog.Logger,
+	dest, fpath string,
+	opts ChromePrintOptions,
+) error {
+	const op string = "prinery.pm2.Markdown"
+	resolver := func() error {
+		if m.chromeUnit == nil {
+			return errors.New("cannot handle Markdown print request as there is no chromeUnit")
+		}
+		p, err := newMarkdownPrinter(logger, fpath, opts)
+		if err != nil {
+			return err
+		}
+		req := request{
+			ctx:     ctx,
+			logger:  logger,
+			printer: p,
+			dest:    dest,
+			result:  make(chan error),
+		}
+		m.chromeUnit.dispatch(req)
+		err = <-req.result
+		return err
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (m *pm2) Office(
+	ctx context.Context,
+	logger xlog.Logger,
+	dest string,
+	fpaths []string,
+	opts UnoconvPrintOptions,
+) error {
+	const op string = "prinery.pm2.Office"
+	resolver := func() error {
+		if m.sofficeUnit == nil {
+			return errors.New("cannot handle Office print request as there is no sofficeUnit")
+		}
+		p := unoconvPrinter{
+			logger: logger,
+			fpaths: fpaths,
+			opts:   opts,
+		}
+		req := request{
+			ctx:     ctx,
+			logger:  logger,
+			printer: p,
+			dest:    dest,
+			result:  make(chan error),
+		}
+		m.sofficeUnit.dispatch(req)
+		err := <-req.result
+		return err
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (m *pm2) Merge(
+	ctx context.Context,
+	logger xlog.Logger,
+	dest string,
+	fpaths []string,
+) error {
+	const op string = "prinery.pm2.Merge"
+	p := mergePrinter{
+		logger: logger,
+		fpaths: fpaths,
+	}
+	if err := p.print(ctx, nil, dest); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (m *pm2) start(p process) error {
+	const op string = "prinery.pm2.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 *pm2) restart(p process) error {
+	const op string = "prinery.pm2.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.spec().id())
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (m *pm2) isViable(p process) bool {
+	if !p.viabilityFunc()(m.logger) {
+		return false
+	}
+	/*m.listLock.Lock()
+	defer m.listLock.Unlock()
+	return m.list.isOnline(p)*/
+	return true
+}
+
+func (m *pm2) warmup(p process) {
+	const op string = "prinery.pm2.warmup"
+	warmupTime := p.warmupTime()
+	m.logger.DebugfOp(
+		op,
+		"waiting '%v' for allowing '%s' to warmup",
+		warmupTime,
+		p.spec().id(),
+	)
+	time.Sleep(warmupTime)
+}
+
+func (m *pm2) logs(p process) error {
+	const op string = "prinery.pm2.logs"
+	if m.config.LogLevel() == xlog.DebugLevel {
+		if err := m.run(logsCommand, p); err != nil {
+			return xerror.New(op, err)
+		}
+	}
+	return nil
+}
+
+func (m *pm2) run(pm2Cmd command, p process) error {
+	const op string = "prinery.pm2.run"
+	resolver := func() error {
+		args := []string{
+			string(pm2Cmd),
+		}
+		if pm2Cmd == startCommand {
+			args = append(args, p.binary())
+			args = append(args, fmt.Sprintf("--name=%s", p.spec().id()))
+			args = append(args, "--interpreter=none", "--")
+			args = append(args, p.args()...)
+		} else {
+			args = append(args, p.spec().id())
+		}
+		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 (
+	_ = Prinery(new(pm2))
+)

internal/pkg/prinery/prinery.go

@@ -2,122 +2,89 @@ package prinery
 
 import (
 	"context"
-	"fmt"
+	"time"
 
-	"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 processSpec interface {
+	id() string
+	host() string
+	port() uint
 }
 
-type worker struct {
-	work chan request
-	proc process.Process
+type process interface {
+	spec() processSpec
+	binary() string
+	args() []string
+	warmupTime() time.Duration
+	viabilityFunc() func(logger xlog.Logger) bool
 }
 
-func (w *worker) do(done chan *worker) {
-	for {
-		req := <-w.work
-		req.result <- req.print.Print(req.ctx, req.dest, w.proc)
-		done <- w
+func processesToSpecs(processes []process) []processSpec {
+	specs := make([]processSpec, len(processes))
+	for i, p := range processes {
+		specs[i] = p.spec()
+	}
+	return specs
+}
+
+type printer interface {
+	print(ctx context.Context, spec processSpec, dest string) error
+}
+
+// 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,
 	}
 }
 
-type Prinery struct {
-	logger  xlog.Logger
-	manager process.Manager
-	work    chan request
-	pool    chan *worker
-	done    chan *worker
+// UnoconvPrintOptions helps customizing the
+// LibreOffice print result.
+type UnoconvPrintOptions struct {
+	Landscape bool
 }
 
-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)
-		}
+// DefaultUnoconvPrinterOptions returns the default
+// LibreOffice print options.
+func DefaultUnoconvPrinterOptions() UnoconvPrintOptions {
+	return UnoconvPrintOptions{
+		Landscape: false,
 	}
 }
 
-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
-	}()
-
+type Prinery interface {
+	Start(emergency chan error) error
+	HTML(ctx context.Context, logger xlog.Logger, dest, fpath string, opts ChromePrintOptions) error
+	URL(ctx context.Context, logger xlog.Logger, dest, URL string, opts ChromePrintOptions) error
+	Markdown(ctx context.Context, logger xlog.Logger, dest, fpath string, opts ChromePrintOptions) error
+	Office(ctx context.Context, logger xlog.Logger, dest string, fpaths []string, opts UnoconvPrintOptions) error
+	Merge(ctx context.Context, logger xlog.Logger, dest string, fpaths []string) error
 }

internal/pkg/prinery/soffice.go

@@ -0,0 +1,158 @@
+package prinery
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+
+	"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 sofficeProcess struct {
+	unoPort uint
+}
+
+func newSofficesProcesses(nInstances int64) []process {
+	processes := make([]process, nInstances)
+	var i int64
+	var currentPort uint = 2002
+	for i = 0; i < nInstances; i++ {
+		processes[i] = sofficeProcess{
+			unoPort: currentPort,
+		}
+		currentPort++
+	}
+	return processes
+}
+
+func (p sofficeProcess) id() string {
+	return fmt.Sprintf("%s-%d", p.binary(), p.port())
+}
+
+func (p sofficeProcess) host() string {
+	return "127.0.0.1"
+}
+
+func (p sofficeProcess) port() uint {
+	return p.unoPort
+}
+
+func (p sofficeProcess) spec() processSpec {
+	return p
+}
+
+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 = "prinery.sofficeProcess.viabilityFunc"
+	return func(logger xlog.Logger) bool {
+		// TODO find a way to check.
+		return true
+	}
+}
+
+type unoconvPrinter struct {
+	logger xlog.Logger
+	fpaths []string
+	opts   UnoconvPrintOptions
+}
+
+func (p unoconvPrinter) print(ctx context.Context, spec processSpec, dest string) error {
+	const op string = "prinery.unoconvPrinter.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 := p.unoconv(ctx, spec, fpath, tmpDest); 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 := mergePrinter{
+			logger: p.logger,
+			fpaths: fpaths,
+		}
+		return merger.print(ctx, nil, dest)
+	}
+	if err := resolver(); err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (p unoconvPrinter) unoconv(ctx context.Context, spec processSpec, fpath, dest string) error {
+	const op string = "prinery.unoconvPrinter.unoconv"
+	resolver := func() error {
+		args := []string{
+			"--server",
+			spec.host(),
+			"--port",
+			fmt.Sprintf("%d", spec.port()),
+			"--format",
+			"pdf",
+		}
+		if p.opts.Landscape {
+			args = append(args, "--printer", "PaperOrientation=landscape")
+		}
+		args = append(args, "--output", dest, fpath)
+		cmd, err := xexec.CommandContext(
+			ctx,
+			p.logger,
+			"unoconv",
+			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
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = processSpec(new(sofficeProcess))
+	_ = process(new(sofficeProcess))
+	_ = printer(new(unoconvPrinter))
+)

internal/pkg/prinery/unit.go

@@ -0,0 +1,125 @@
+package prinery
+
+import (
+	"context"
+	"errors"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
+)
+
+type request struct {
+	ctx     context.Context
+	logger  xlog.Logger
+	printer printer
+	dest    string
+	result  chan error
+}
+
+type worker struct {
+	work chan request
+	spec processSpec
+}
+
+func (w *worker) do(done chan *worker) {
+	for {
+		req := <-w.work
+		req.result <- req.printer.print(req.ctx, w.spec, req.dest)
+		done <- w
+	}
+}
+
+type unit struct {
+	logger  xlog.Logger
+	workers []*worker
+	work    chan request
+	pool    chan *worker
+	done    chan *worker
+}
+
+func newUnit(logger xlog.Logger, specs []processSpec) (*unit, error) {
+	const op string = "prinery.newUnit"
+	resolver := func() (*unit, error) {
+		nWorkers := len(specs)
+		if nWorkers == 0 {
+			return nil, errors.New("no workers to create")
+		}
+		logger.DebugfOp(op, "creating '%d' workers...", nWorkers)
+		workers := make([]*worker, nWorkers)
+		work := make(chan request, 1)
+		pool := make(chan *worker, nWorkers)
+		done := make(chan *worker, nWorkers)
+		for i, spec := range specs {
+			w := &worker{
+				work: work,
+				spec: spec,
+			}
+			logger.DebugfOp(op, "worker '%s' created", w.spec.id())
+			workers[i] = w
+		}
+		return &unit{
+			logger:  logger,
+			workers: workers,
+			work:    work,
+			pool:    pool,
+			done:    done,
+		}, nil
+	}
+	u, err := resolver()
+	if err != nil {
+		return nil, xerror.New(op, err)
+	}
+	return u, nil
+}
+
+func (u *unit) start(emergency chan error) {
+	const op string = "prinery.unit.start"
+	for _, w := range u.workers {
+		u.logger.DebugfOp(op, "starting worker '%s'...", w.spec.id())
+		go w.do(u.done)
+		u.pool <- w
+	}
+	for {
+		select {
+		case req := <-u.work:
+			u.dispatch(req)
+		case w := <-u.done:
+			u.completed(w, emergency)
+		}
+	}
+}
+
+func (u *unit) request(ctx context.Context, logger xlog.Logger, printer printer, dest string) error {
+	const op string = "prinery.unit.request"
+	req := request{
+		ctx:     ctx,
+		logger:  logger,
+		printer: printer,
+		dest:    dest,
+		result:  make(chan error),
+	}
+	u.dispatch(req)
+	err := <-req.result
+	if err != nil {
+		return xerror.New(op, err)
+	}
+	return nil
+}
+
+func (u *unit) dispatch(req request) {
+	const op string = "prinery.unit.dispatch"
+	select {
+	case w := <-u.pool:
+		u.logger.DebugfOp(op, "worker '%s' is now in use", w.spec.id())
+		w.work <- req
+	case <-req.ctx.Done():
+		req.result <- xerror.New(op, req.ctx.Err())
+	}
+}
+
+func (u *unit) completed(w *worker, emergency chan error) {
+	const op string = "prinery.unit.completed"
+	// TODO check viability, handles errors via emergency chan.
+	u.logger.DebugfOp(op, "worker '%s' is ready for a new request", w.spec.id())
+	u.pool <- w
+}

internal/pkg/print/html.go

@@ -1,18 +0,0 @@
-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,
-	}
-}

internal/pkg/print/office.go

@@ -52,7 +52,14 @@ func (p officePrint) Print(ctx context.Context, dest string, proc process.Proces
 			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 {
+			if err := unoconv(
+				ctx,
+				p.logger,
+				proc,
+				p.opts,
+				fpath,
+				tmpDest,
+			); err != nil {
 				return err
 			}
 			p.logger.DebugfOp(op, "'%s.pdf' created", baseFilename)
@@ -74,10 +81,20 @@ func (p officePrint) Print(ctx context.Context, dest string, proc process.Proces
 	return nil
 }
 
-func unoconv(ctx context.Context, logger xlog.Logger, fpath, dest string, opts OfficePrintOptions) error {
+func unoconv(
+	ctx context.Context,
+	logger xlog.Logger,
+	proc process.Process,
+	opts OfficePrintOptions,
+	fpath, dest string,
+) error {
 	const op string = "print.unoconv"
 	resolver := func() error {
 		args := []string{
+			"--server",
+			proc.Host(),
+			"--port",
+			fmt.Sprintf("%d", proc.Port()),
 			"--format",
 			"pdf",
 		}