Only allow one instance of automedia to run at once (pid file)

2 files changed, 28 insertions, 1 deletions

diff --git a/README.md b/README.md
index 3da4a0a..a85dee1 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,6 @@ Run automedia without any options to see all options.
 ## TODO
 1. Periodically check and remove in_progress files and their directories. This can happen if the computer crashes while adding rss.
 2. Automatically remove torrents that have finished seeding, to reduce memory usage and startup time of transmission.
-3. Only allow one instance of automedia to run at a time. This is to prevent the config from being corrupt.
 # Requirements
 ## System
 transmission-cli, notify-send (optional)
diff --git a/automedia.py b/automedia.py
index 272f853..2d8f300 100755
--- a/automedia.py
+++ b/automedia.py
@@ -7,6 +7,8 @@ import sys
 import time
 import json
 import uuid
+import errno
+import signal
 import transmissionrpc
 
 from domain import url_extract_domain
@@ -19,6 +21,7 @@ script_dir = os.path.dirname(os.path.realpath(sys.argv[0]))
 config_dir = os.path.expanduser("~/.config/automedia")
 rss_config_dir = os.path.join(config_dir, "rss")
 html_config_dir = os.path.join(config_dir, "html")
+automedia_pid_path = "/tmp/automedia.pid"
 
 only_show_finished_notification = True
 
@@ -721,6 +724,31 @@ def command_sync(args):
     if not download_dir:
         usage_sync()
 
+    pid_file = None
+    while True:
+        try:
+            pid_file = os.open(automedia_pid_path, os.O_CREAT | os.O_EXCL | os.O_WRONLY)
+            break
+        except OSError as e:
+            if e.errno != errno.EEXIST:
+                raise
+
+            running_automedia_pid = get_file_content_or_none(automedia_pid_path)
+            if running_automedia_pid:
+                cmdline = get_file_content_or_none("/proc/%s/cmdline" % running_automedia_pid)
+                if cmdline and "automedia.py" in cmdline and "sync" in cmdline:
+                    print("AutoMedia is already running with sync")
+                    exit(0)
+            os.remove(automedia_pid_path)
+
+    def signal_handler(signum, frame):
+        os.unlink(automedia_pid_path)
+        exit(1)
+    signal.signal(signal.SIGINT, signal_handler)
+
+    os.write(pid_file, ("%s" % os.getpid()).encode())
+    os.close(pid_file)
+
     os.makedirs(rss_config_dir, exist_ok=True)
     os.makedirs(html_config_dir, exist_ok=True)