X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/ff2e2d7b53edfec33a77ad1ff2b5a83f02a5be80..3bbb988777079718338e3e6cb9c6c9b5399be800:/sdk/python/arvados/events.py

diff --git a/sdk/python/arvados/events.py b/sdk/python/arvados/events.py
index b7d610d66e..d1abc0f7de 100644
--- a/sdk/python/arvados/events.py
+++ b/sdk/python/arvados/events.py
@@ -1,5 +1,5 @@
 from ws4py.client.threadedclient import WebSocketClient
-import thread
+import threading
 import json
 import os
 import time
@@ -7,6 +7,7 @@ import ssl
 import re
 import config
 import logging
+import arvados
 
 _logger = logging.getLogger('arvados.events')
 
@@ -18,13 +19,12 @@ class EventClient(WebSocketClient):
             ssl_options={'cert_reqs': ssl.CERT_NONE}
         else:
             ssl_options={'cert_reqs': ssl.CERT_REQUIRED}
-
-        super(EventClient, self).__init__(url, ssl_options)
+        super(EventClient, self).__init__(url, ssl_options=ssl_options)
         self.filters = filters
         self.on_event = on_event
 
     def opened(self):
-        self.send(json.dumps({"method": "subscribe", "filters": self.filters}))
+        self.subscribe(self.filters)
 
     def received_message(self, m):
         self.on_event(json.loads(str(m)))
@@ -36,14 +36,93 @@ class EventClient(WebSocketClient):
         except:
             pass
 
-def subscribe(api, filters, on_event):
+    def subscribe(self, filters, last_log_id=None):
+        m = {"method": "subscribe", "filters": filters}
+        if last_log_id is not None:
+            m["last_log_id"] = last_log_id
+        self.send(json.dumps(m))
+
+    def unsubscribe(self, filters):
+        self.send(json.dumps({"method": "unsubscribe", "filters": filters}))
+
+class PollClient(threading.Thread):
+    def __init__(self, api, filters, on_event, poll_time):
+        super(PollClient, self).__init__()
+        self.api = api
+        if filters:
+            self.filters = [filters]
+        else:
+            self.filters = [[]]
+        self.on_event = on_event
+        self.poll_time = poll_time
+        self.stop = threading.Event()
+
+    def run(self):
+        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.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.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
-    try:
-        url = "{}?api_token={}".format(api._rootDesc['websocketUrl'], config.get('ARVADOS_API_TOKEN'))
-        ws = EventClient(url, filters, on_event)
-        ws.connect()
-        return ws
-    except Exception:
-        if (ws):
-          ws.close_connection()
-        raise
+    if 'websocketUrl' in api._rootDesc:
+        try:
+            url = "{}?api_token={}".format(api._rootDesc['websocketUrl'], api.api_token)
+            ws = EventClient(url, filters, on_event)
+            ws.connect()
+            return ws
+        except Exception as e:
+            _logger.warn("Got exception %s trying to connect to websockets at %s" % (e, api._rootDesc['websocketUrl']))
+            if ws:
+                ws.close_connection()
+    if poll_fallback:
+        _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("Websockets not available")
+        return None