Add support for using polling to detect changes.

Closes #4

README.md

@@ -56,6 +56,7 @@ This example is to run a permissions-repairing utility whenever there's a change
     UMASK=0000
     # This is important because chmod/chown will change files in the monitored directory
     IGNORE_EVENTS_WHILE_COMMAND_IS_RUNNING=1
+    USE_POLLING=no
 
 Since the `newperms` utility does an explicit "chown -R nobody:users", we need to use the UMAP and GMAP environment variables to update the user and group in the container so that it will match the host. For example:
 
@@ -73,5 +74,6 @@ This example tells SageTV to rescan its imported media when the media directory
     GROUP_ID=0
     UMASK=0000
     IGNORE_EVENTS_WHILE_COMMAND_IS_RUNNING=0
+    USE_POLLING=no
 
 We don't need to ignore events while the command is running because the wget command is a "fire and forget" asynchronous operation. We also don't need to use UMAP or GMAP.

monitor.py

@@ -10,6 +10,7 @@ import sys
 import tempfile
 import time
 from watchdog.observers import Observer
+from watchdog.observers.polling import PollingObserver
 from watchdog.events import FileSystemEventHandler
 
 RUNAS = "/files/runas.sh"
@@ -124,6 +125,15 @@ def read_config(config_file):
         sys.exit(1)
     args.ignore_events_while_command_is_running = env["IGNORE_EVENTS_WHILE_COMMAND_IS_RUNNING"] == "1"
 
+    if "USE_POLLING" in env:
+        if not re.match("(yes|no|true|false|0|1)", env["USE_POLLING"], re.IGNORECASE):
+            logging.error("Configuration error. USE_POLLING must be \"yes\" or \"no\".")
+            sys.exit(1)
+
+        args.use_polling = True if re.match("(yes|true|1)", env["USE_POLLING"], re.IGNORECASE) else False
+    else:
+        args.use_polling = False
+
     logging.info("CONFIGURATION:")
     logging.info("      WATCH_DIR=%s", args.watch_dir)
     logging.info("SETTLE_DURATION=%s", args.settle_duration)
@@ -134,6 +144,7 @@ def read_config(config_file):
     logging.info("       GROUP_ID=%s", args.group_id)
     logging.info("          UMASK=%s", args.umask)
     logging.info("          DEBUG=%s", args.debug)
+    logging.info("    USE_POLLING=%s", args.use_polling)
     logging.info("IGNORE_EVENTS_WHILE_COMMAND_IS_RUNNING=%s", args.ignore_events_while_command_is_running)
 
     return args
@@ -258,8 +269,14 @@ if args.debug:
 logging.info("Starting monitor for %s", name)
 
 # Launch the watchdog
+if args.use_polling:
+    logging.info("Using polling to detect changes")
+    observer = PollingObserver()
+else:
+    logging.info("Using native change detection to detect changes")
+    observer = Observer()
+
 event_handler = ModifyHandler()
-observer = Observer()
 observer.schedule(event_handler, args.watch_dir, recursive=True)
 observer.start()
 

sample.conf

@@ -39,5 +39,8 @@ UMASK=0
 # file even if it already has that mode.
 IGNORE_EVENTS_WHILE_COMMAND_IS_RUNNING=1
 
+# Set to true to use polling to detect changes. For non-linux file systems, such as Windows shares, you must use polling.
+USE_POLLING=no
+
 # Set this to 1 to log all events, for debugging purposes. WARNING! This creates copious amounts of confusing logging!
 DEBUG=0