Add global downloader lock

sync.py

@@ -1,8 +1,12 @@
 from urllib.parse import urlparse, quote
 from pathlib import Path
+import os.path
+import os
 import configparser
 import subprocess
-import pdb
+import datetime
+import time
+import sys
 
 def read_config():
     config = configparser.RawConfigParser()
@@ -26,7 +30,31 @@ def download_channel(target_directory, channel_url, options="", update_mpd=False
     p = subprocess.Popen(["youtube-dl", *options.split(" "), *mpd_update_options, channel_url], cwd=target_directory)
     p.wait()
 
+def lock_downloader():
+    if os.path.isfile("lockfile"):
+        return False
+    else:
+        with open("lockfile", "w") as fd:
+            print("Creating lockfile")
+            timestamp = int(datetime.datetime.now().timestamp())
+            fd.write(str(timestamp) + "\n")
+        return True
+
+def unlock_downloader():
+    os.remove("lockfile")
+
+
+lock_success = lock_downloader()
+if not lock_success:
+    with open("lockfile", "r") as fd:
+        timestamp = fd.readline().strip()
+    time = datetime.datetime.fromtimestamp(int(timestamp))
+    print("Downloader already running. It was started at {}".format(time))
+    sys.exit(1)
+
 config = read_config()
 mixes = get_mixes(config["general"]["mixes_dir"])
 for folder,url in mixes:
     download_channel(folder, url, config["youtube-dl"]["options"], update_mpd=config["mpd"]["update"], mpd_root=config["mpd"]["mpd_root"])
+print("Download operation finished. Releasing lockfile now.")
+unlock_downloader()