update.py: add an option --timeout for lockfile

We have an update.py running periodically in background, but we also
need to run it manually, for example, run it to update actual_branch,
the manually run usually failed because can't get lockfile, we have to
run it again and again. A timeout option helps a lot in such a case. Now
the following command can make sure we can run the command successfully:

$ update.py -b master -a actual_branch -t 2000

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

layerindex/update.py

@@ -156,6 +156,9 @@ def main():
     parser.add_option("-l", "--layer",
             help = "Specify layers to update (use commas to separate multiple). Default is all published layers.",
             action="store", dest="layers")
+    parser.add_option("-t", "--timeout",
+            help = "Specify timeout in seconds to get layerindex.lock. Default is 30 seconds.",
+            type="int", action="store", dest="timeout", default=30)
     parser.add_option("-r", "--reload",
             help = "Reload recipe data instead of updating since last update",
             action="store_true", dest="reload")
@@ -265,7 +268,7 @@ def main():
         update.save()
     try:
         lockfn = os.path.join(fetchdir, "layerindex.lock")
-        lockfile = utils.lock_file(lockfn)
+        lockfile = utils.lock_file(lockfn, options.timeout, logger)
         if not lockfile:
             logger.error("Layer index lock timeout expired")
             sys.exit(1)

layerindex/utils.py

@@ -309,8 +309,10 @@ class ListHandler(logging.Handler):
         return log
 
 
-def lock_file(fn):
-    starttime = time.time()
+def lock_file(fn, timeout=30, logger=None):
+    start = time.time()
+    last = start
+    counter = 1
     while True:
         lock = open(fn, 'w')
         try:
@@ -318,8 +320,14 @@ def lock_file(fn):
             return lock
         except IOError:
             lock.close()
-            if time.time() - starttime > 30:
+            current = time.time()
+            if current - start > timeout:
                 return None
+            # Print a message in every 5 seconds
+            if logger and (current - last > 5):
+                last = current
+                logger.info('Trying to get lock on %s (tried %s seconds) ...' % (fn, (5 * counter)))
+                counter += 1
 
 def unlock_file(lock):
     fcntl.flock(lock, fcntl.LOCK_UN)