X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/758d59141102b29371f44512671b9efe0cf62821..3db43f179cf2fe1fb4077f8789d2b53588806517:/sdk/python/arvados/events.py

diff --git a/sdk/python/arvados/events.py b/sdk/python/arvados/events.py
index 489be5a0ee..d1abc0f7de 100644
--- a/sdk/python/arvados/events.py
+++ b/sdk/python/arvados/events.py
@@ -7,6 +7,7 @@ import ssl
 import re
 import config
 import logging
+import arvados
 
 _logger = logging.getLogger('arvados.events')
 
@@ -48,37 +49,64 @@ class PollClient(threading.Thread):
     def __init__(self, api, filters, on_event, poll_time):
         super(PollClient, self).__init__()
         self.api = api
-        self.filters = filters
-        self.on_event = on_event
-        items = self.api.logs().list(limit=1, order=["id desc"], filters=filters).execute()['items']
-        if len(items) > 0:
-            self.id = items[0]["id"]
+        if filters:
+            self.filters = [filters]
         else:
-            self.id = 0
+            self.filters = [[]]
+        self.on_event = on_event
         self.poll_time = poll_time
-        self.loop = True
-        self.on_event({'status': 200})
+        self.stop = threading.Event()
 
     def run(self):
-        while self.loop:
-            time.sleep(self.poll_time)
-            items = self.api.logs().list(order=["id asc"], filters=self.filters+[["id", ">", str(self.id)]]).execute()['items']
-            for i in items:
-                self.id = i['id']
-                self.on_event(i)
+        self.id = 0
+        for f in self.filters:
+            items = self.api.logs().list(limit=1, order="id desc", filters=f).execute()['items']
+            if items:
+                if items[0]['id'] > self.id:
+                    self.id = items[0]['id']
+
+        self.on_event({'status': 200})
+
+        while not self.stop.isSet():
+            max_id = self.id
+            for f in self.filters:
+                items = self.api.logs().list(order="id asc", filters=f+[["id", ">", str(self.id)]]).execute()['items']
+                for i in items:
+                    if i['id'] > max_id:
+                        max_id = i['id']
+                    self.on_event(i)
+            self.id = max_id
+            self.stop.wait(self.poll_time)
+
+    def run_forever(self):
+        self.stop.wait()
 
     def close(self):
-        self.loop = False
-        self.join()
+        self.stop.set()
+        try:
+            self.join()
+        except RuntimeError:
+            # "join() raises a RuntimeError if an attempt is made to join the
+            # current thread as that would cause a deadlock. It is also an
+            # error to join() a thread before it has been started and attempts
+            # to do so raises the same exception."
+            pass
 
     def subscribe(self, filters):
         self.on_event({'status': 200})
-        self.filters += filters
+        self.filters.append(filters)
 
     def unsubscribe(self, filters):
         del self.filters[self.filters.index(filters)]
 
+
 def subscribe(api, filters, on_event, poll_fallback=15):
+    '''
+    api: Must be a newly created from arvados.api(cache=False), not shared with the caller, as it may be used by a background thread.
+    filters: Initial subscription filters.
+    on_event: The callback when a message is received
+    poll_fallback: If websockets are not available, fall back to polling every N seconds.  If poll_fallback=False, this will return None if websockets are not available.
+    '''
     ws = None
     if 'websocketUrl' in api._rootDesc:
         try:
@@ -87,14 +115,14 @@ def subscribe(api, filters, on_event, poll_fallback=15):
             ws.connect()
             return ws
         except Exception as e:
-            _logger.warn("Got exception %s trying to connect to web sockets" % e)
+            _logger.warn("Got exception %s trying to connect to websockets at %s" % (e, api._rootDesc['websocketUrl']))
             if ws:
-                ws.close()
+                ws.close_connection()
     if poll_fallback:
-        _logger.warn("Web sockets not available, falling back to log table polling")
+        _logger.warn("Websockets not available, falling back to log table polling")
         p = PollClient(api, filters, on_event, poll_fallback)
         p.start()
         return p
     else:
-        _logger.error("Web sockets not available")
+        _logger.error("Websockets not available")
         return None