X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/9af0808e182e297b9c957c93f629016e1517eba1..6e5e1c725a10ea791f00d073003175ac3c29a6c7:/sdk/python/arvados/events.py

diff --git a/sdk/python/arvados/events.py b/sdk/python/arvados/events.py
index fc86cb46d4..b1872002eb 100644
--- a/sdk/python/arvados/events.py
+++ b/sdk/python/arvados/events.py
@@ -1,33 +1,37 @@
-from ws4py.client.threadedclient import WebSocketClient
-import threading
+import arvados
+import config
+import errors
+
+import logging
 import json
-import os
+import threading
 import time
-import ssl
+import os
 import re
-import config
-import logging
-import arvados
+import ssl
+from ws4py.client.threadedclient import WebSocketClient
 
 _logger = logging.getLogger('arvados.events')
 
 class EventClient(WebSocketClient):
-    def __init__(self, url, filters, on_event):
-        # Prefer system's CA certificates (if available)
-        ssl_options = {}
-        certs_path = '/etc/ssl/certs/ca-certificates.crt'
-        if os.path.exists(certs_path):
-            ssl_options['ca_certs'] = certs_path
+    def __init__(self, url, filters, on_event, last_log_id):
+        ssl_options = {'ca_certs': arvados.util.ca_certs_path()}
         if config.flag_is_true('ARVADOS_API_HOST_INSECURE'):
             ssl_options['cert_reqs'] = ssl.CERT_NONE
         else:
             ssl_options['cert_reqs'] = ssl.CERT_REQUIRED
+
+        # Warning: If the host part of url resolves to both IPv6 and
+        # IPv4 addresses (common with "localhost"), only one of them
+        # will be attempted -- and it might not be the right one. See
+        # ws4py's WebSocketBaseClient.__init__.
         super(EventClient, self).__init__(url, ssl_options=ssl_options)
         self.filters = filters
         self.on_event = on_event
+        self.last_log_id = last_log_id
 
     def opened(self):
-        self.subscribe(self.filters)
+        self.subscribe(self.filters, self.last_log_id)
 
     def received_message(self, m):
         self.on_event(json.loads(str(m)))
@@ -58,6 +62,7 @@ class PollClient(threading.Thread):
             self.filters = [[]]
         self.on_event = on_event
         self.poll_time = poll_time
+        self.daemon = True
         self.stop = threading.Event()
 
     def run(self):
@@ -105,29 +110,43 @@ class PollClient(threading.Thread):
         del self.filters[self.filters.index(filters)]
 
 
-def subscribe(api, filters, on_event, poll_fallback=15):
-    '''
-    api: a client object retrieved from arvados.api(). The caller should not use this client object for anything else after calling subscribe().
-    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:
-            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
+def _subscribe_websocket(api, filters, on_event, last_log_id=None):
+    endpoint = api._rootDesc.get('websocketUrl', None)
+    if not endpoint:
+        raise errors.FeatureNotEnabledError(
+            "Server does not advertise a websocket endpoint")
+    uri_with_token = "{}?api_token={}".format(endpoint, api.api_token)
+    client = EventClient(uri_with_token, filters, on_event, last_log_id)
+    ok = False
+    try:
+        client.connect()
+        ok = True
+        return client
+    finally:
+        if not ok:
+            client.close_connection()
+
+def subscribe(api, filters, on_event, poll_fallback=15, last_log_id=None):
+    """
+    :api:
+      a client object retrieved from arvados.api(). The caller should not use this client object for anything else after calling subscribe().
+    :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.
+    :last_log_id:
+      Log rows that are newer than the log id
+    """
+
+    if not poll_fallback:
+        return _subscribe_websocket(api, filters, on_event, last_log_id)
+
+    try:
+        return _subscribe_websocket(api, filters, on_event, last_log_id)
+    except Exception as e:
+        _logger.warn("Falling back to polling after websocket error: %s" % e)
+    p = PollClient(api, filters, on_event, poll_fallback)
+    p.start()
+    return p