From b24b1e07d293ff3a82f1154948dc87615da7dc6f Mon Sep 17 00:00:00 2001
From: "dylan.frei" <dylan.frei@etu.hesge.ch>
Date: Sun, 26 Mar 2023 22:14:01 +0200
Subject: [PATCH] Added mutex for concurrency
---
api.go | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/api.go b/api.go
index 588dd8c..8cae4aa 100644
--- a/api.go
+++ b/api.go
@@ -18,9 +18,13 @@ import (
"path/filepath"
"strconv"
"strings"
+ "sync"
"syscall"
+ "time"
)
+var m sync.Mutex
+
func main() {
if _, err := os.Stat("/var/lib/image-viewer"); err != nil {
@@ -86,9 +90,9 @@ func Stop(c echo.Context) error {
}
func Upload(c echo.Context) error {
- //-----------
- // Read file
- //-----------
+ //protect ressources
+ m.Lock()
+ defer m.Unlock()
// Source
file, err := c.FormFile("file")
@@ -139,6 +143,10 @@ func List(c echo.Context) error {
}
func Del(c echo.Context) error {
+ //protect ressources
+ m.Lock()
+ defer m.Unlock()
+
// Removing file from the directory
// Using Remove() function
img := c.Param("img")
@@ -150,6 +158,9 @@ func Del(c echo.Context) error {
}
func Display(c echo.Context) error {
+ //protect ressources
+ m.Lock()
+ defer m.Unlock()
//Check if program is running
if _, err := os.Stat("/var/run/image-viewer.pid"); err != nil {
@@ -187,6 +198,10 @@ func Display(c echo.Context) error {
}
syscall.Kill(pid, syscall.SIGUSR1)
+ //Ensure image has the time to be displayed before mutex release
+ //In case a subsequent call to display would be made before the signal is processed by the backend,
+ //the data from current.ppm could be corrupted (or too long) during process.
+ time.Sleep(500 * time.Millisecond)
return c.String(http.StatusOK, img+" is being displayed\n")
}
--
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