From d35e0e0d0ba2b9c8e9dbc3061462c6c321dae3ce Mon Sep 17 00:00:00 2001
From: Nova Kwok <n0vad3v@riseup.net>
Date: Fri, 29 Dec 2023 19:38:05 +0800
Subject: [PATCH] Lock on convert (#307)

* Lock on convert

* Fix typo

* Should use debug for convert lock

* Bump to 0.10.5
---
 config/config.go   |  3 ++-
 encoder/encoder.go | 26 ++++++++++++++++++++++----
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/config/config.go b/config/config.go
index 4157da374..50c875c6c 100644
--- a/config/config.go
+++ b/config/config.go
@@ -46,8 +46,9 @@ var (
 	ProxyMode      bool
 	Prefetch       bool
 	Config         = NewWebPConfig()
-	Version        = "0.10.4"
+	Version        = "0.10.5"
 	WriteLock      = cache.New(5*time.Minute, 10*time.Minute)
+	ConvertLock    = cache.New(5*time.Minute, 10*time.Minute)
 	RemoteRaw      = "./remote-raw"
 	Metadata       = "./metadata"
 	LocalHostAlias = "local"
diff --git a/encoder/encoder.go b/encoder/encoder.go
index 7e20cf992..c4b77b301 100644
--- a/encoder/encoder.go
+++ b/encoder/encoder.go
@@ -6,6 +6,7 @@ import (
 	"runtime"
 	"strings"
 	"sync"
+	"time"
 	"webp_server_go/config"
 	"webp_server_go/helper"
 
@@ -33,7 +34,24 @@ func init() {
 }
 
 func ConvertFilter(rawPath, avifPath, webpPath string, extraParams config.ExtraParams, c chan int) {
-	// all absolute paths
+	// Wait for the conversion to complete and return the converted image
+	retryDelay := 100 * time.Millisecond // Initial retry delay
+
+	for {
+		if _, found := config.ConvertLock.Get(rawPath); found {
+			log.Debugf("file %s is locked under conversion, retrying in %s", rawPath, retryDelay)
+			time.Sleep(retryDelay)
+		} else {
+			// The lock is released, indicating that the conversion is complete
+			break
+		}
+	}
+
+	// If there is a lock here, it means that another thread is converting the same image
+	// Lock rawPath to prevent concurrent conversion
+	config.ConvertLock.Set(rawPath, true, -1)
+	defer config.ConvertLock.Delete(rawPath)
+
 	var wg sync.WaitGroup
 	wg.Add(2)
 	if !helper.ImageExists(avifPath) && config.Config.EnableAVIF {
@@ -77,9 +95,9 @@ func convertImage(rawPath, optimizedPath, imageType string, extraParams config.E
 		var convertedRaw, converted = ConvertRawToJPG(rawPath, optimizedPath)
 		// If converted, use converted file as raw
 		if converted {
-			// Use converted file(JPG) as raw input for further convertion
+			// Use converted file(JPG) as raw input for further conversion
 			rawPath = convertedRaw
-			// Remove converted file after convertion
+			// Remove converted file after conversion
 			defer func() {
 				log.Infoln("Removing intermediate conversion file:", convertedRaw)
 				err := os.Remove(convertedRaw)
@@ -105,6 +123,7 @@ func convertImage(rawPath, optimizedPath, imageType string, extraParams config.E
 	case "avif":
 		err = avifEncoder(img, rawPath, optimizedPath, extraParams)
 	}
+
 	return err
 }
 
@@ -179,7 +198,6 @@ func webpEncoder(img *vips.ImageRef, rawPath string, optimizedPath string, extra
 			}
 		}
 		buf, _, err = img.ExportWebp(&ep)
-
 	}
 
 	if err != nil {