Reap stale sync runners after a minute dead

If the client never claims the result, delete the sync task.

confluent_server/confluent/syncfiles.py

@@ -285,9 +285,10 @@ def mkpathorlink(source, destination, appendexist=False):
 
 
 syncrunners = {}
-
+cleaner = None
 
 def start_syncfiles(nodename, cfg, suffixes, principals=[]):
+    global cleaner
     peerip = None
     if nodename in syncrunners:
         return '503 Synchronization already in progress', 'Synchronization already in progress for {}'.format(nodename)
@@ -319,7 +320,26 @@ def start_syncfiles(nodename, cfg, suffixes, principals=[]):
         return '200 OK', 'Empty synclist'  # the synclist has no actual entries
     syncrunners[nodename] = eventlet.spawn(
         sync_list_to_node, sl, nodename, suffixes, peerip)
-    return '202 Queued', 'Background synchronization initiated' # backgrounded
+    if not cleaner:
+        cleaner = eventlet.spawn(cleanit)
+    return '202 Queued', 'Background synchronization initiated'  # backgrounded
+
+
+def cleanit():
+    toreap = {}
+    while True:
+        for nn in list(syncrunners):
+            if syncrunners[nn].dead:
+                if nn in toreap:
+                    syncrunners[nn].wait()
+                    del syncrunners[nn]
+                    del toreap[nn]
+                else:
+                    toreap[nn] = 1
+            elif nn is in toreap:
+                del toreap[nn]
+            eventlet.sleep(30)
+
 
 def get_syncresult(nodename):
     if nodename not in syncrunners: