From 32f03ab149d100c36a379365b0f50f067cc66093 Mon Sep 17 00:00:00 2001
From: Michael Mayer <michael@liquidbytes.net>
Date: Sat, 1 Feb 2020 23:07:20 +0100
Subject: [PATCH] Backend: Run multiple instances of Sips

---
 internal/photoprism/convert.go | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/internal/photoprism/convert.go b/internal/photoprism/convert.go
index d5b7c90da..fe832066a 100644
--- a/internal/photoprism/convert.go
+++ b/internal/photoprism/convert.go
@@ -88,26 +88,29 @@ func (c *Convert) Start(path string) error {
 }
 
 // ConvertCommand returns the command for converting files to JPEG, depending on the format.
-func (c *Convert) ConvertCommand(image *MediaFile, jpegName string, xmpName string) (result *exec.Cmd, err error) {
+func (c *Convert) ConvertCommand(image *MediaFile, jpegName string, xmpName string) (result *exec.Cmd, useMutex bool, err error) {
 	if image.IsRaw() {
 		if c.conf.SipsBin() != "" {
 			result = exec.Command(c.conf.SipsBin(), "-s", "format", "jpeg", "--out", jpegName, image.fileName)
 		} else if c.conf.DarktableBin() != "" {
+			// Only one instance of darktable-cli allowed due to locking
+			useMutex = true
+
 			if xmpName != "" {
 				result = exec.Command(c.conf.DarktableBin(), image.fileName, xmpName, jpegName)
 			} else {
 				result = exec.Command(c.conf.DarktableBin(), image.fileName, jpegName)
 			}
 		} else {
-			return nil, fmt.Errorf("convert: no binary for raw to jpeg could be found (%s)", image.FileName())
+			return nil, useMutex, fmt.Errorf("convert: no raw to jpeg converter installed (%s)", image.Base())
 		}
 	} else if image.IsHEIF() {
 		result = exec.Command(c.conf.HeifConvertBin(), image.fileName, jpegName)
 	} else {
-		return nil, fmt.Errorf("convert: image type not supported for conversion (%s)", image.Type())
+		return nil, useMutex, fmt.Errorf("convert: image type not supported for conversion (%s)", image.Type())
 	}
 
-	return result, nil
+	return result, useMutex, nil
 }
 
 // ToJpeg converts a single image file to JPEG if possible.
@@ -161,7 +164,7 @@ func (c *Convert) ToJpeg(image *MediaFile) (*MediaFile, error) {
 		return NewMediaFile(jpegName)
 	}
 
-	cmd, err := c.ConvertCommand(image, jpegName, xmpName)
+	cmd, useMutex, err := c.ConvertCommand(image, jpegName, xmpName)
 
 	if err != nil {
 		return nil, err
@@ -171,10 +174,12 @@ func (c *Convert) ToJpeg(image *MediaFile) (*MediaFile, error) {
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 
-	// Make sure only one command is executed at a time.
-	// See https://photo.stackexchange.com/questions/105969/darktable-cli-fails-because-of-locked-database-file
-	c.cmdMutex.Lock()
-	defer c.cmdMutex.Unlock()
+	if useMutex {
+		// Make sure only one command is executed at a time.
+		// See https://photo.stackexchange.com/questions/105969/darktable-cli-fails-because-of-locked-database-file
+		c.cmdMutex.Lock()
+		defer c.cmdMutex.Unlock()
+	}
 
 	// Fetch command output.
 	var out bytes.Buffer