Update GCP Pub/Sub backend

Fixed breaking changes introduced by gcloud-aio dependency.

Closes bmoscon#433

Note: Pinned google_cloud_pubsub~=2.2.0 in setup.py because of an SSL issue in the Pub/Sumb emulator.
google_cloud_pubsub fix is merged, but not on pypi: googleapis/python-pubsub#297

cryptofeed/backends/gcppubsub.py

@@ -36,7 +36,6 @@
 class GCPPubSubCallback:
     def __init__(self, topic: Optional[str] = None, key: Optional[str] = None,
                  service_file: Optional[Union[str, IO[AnyStr]]] = None,
-                 client: Optional[PublisherClient] = None, session: Optional[aiohttp.ClientSession] = None,
                  ordering_key: Optional[Union[str, io.IOBase]] = None, numeric_type=float):
         '''
         Backend using Google Cloud Platform Pub/Sub. Use requires an account with Google Cloud Platform.
@@ -59,10 +58,6 @@ def __init__(self, topic: Optional[str] = None, key: Optional[str] = None,
             or App Engine the environment variable will already be set.
             https://cloud.google.com/bigquery/docs/authentication/service-account-file
             https://cloud.google.com/docs/authentication/production
-        client: PublisherClient
-            Allows gcloud.aio.pubsub.PublisherClient reuse
-        session: ClientSession
-            Allows aiohttp.ClientSession resuse
         ordering_key: str
             if messages have the same ordering key and you publish the messages
             to the same region, subscribers can receive the messages in order
@@ -73,28 +68,43 @@ def __init__(self, topic: Optional[str] = None, key: Optional[str] = None,
         self.numeric_type = numeric_type
         self.topic = topic or f'cryptofeed-{self.key}'
         self.topic_path = self.get_topic()
-        self.session = session or aiohttp.ClientSession()
-        self.client = client or PublisherClient(service_file=service_file, session=self.session)
+        self.service_file = service_file
+        self.session = None
+        self.client = None
 
     def get_topic(self):
         publisher = pubsub_v1.PublisherClient()
         project_id = os.getenv('GCP_PROJECT')
         topic_path = PublisherClient.topic_path(project_id, self.topic)
         try:
-            publisher.create_topic(topic_path)
+            publisher.create_topic(request={"name": topic_path})
         except google.api_core.exceptions.AlreadyExists:
             pass
         finally:
             return topic_path
 
+    async def get_session(self):
+        if not self.session:
+            self.session = aiohttp.ClientSession()
+        return self.session
+
+    async def get_client(self):
+        if not self.client:
+            session = await self.get_session()
+            self.client = PublisherClient(
+                service_file=self.service_file, session=session
+            )
+        return self.client
+
     async def write(self, feed: str, symbol: str, timestamp: float, receipt_timestamp: float, data: dict):
         '''
         Publish message. For filtering, "feed" and "symbol" are added as attributes.
         https://cloud.google.com/pubsub/docs/filtering
         '''
+        client = await self.get_client()
         payload = json.dumps(data).encode()
         message = PubsubMessage(payload, feed=feed, symbol=symbol)
-        await self.client.publish(self.topic_path, [message])
+        await client.publish(self.topic_path, [message])
 
 
 class TradeGCPPubSub(GCPPubSubCallback, BackendTradeCallback):

examples/demo_gcppubsub.py

@@ -6,9 +6,10 @@
 '''
 import os
 import asyncio
-import google.api_core.exceptions
 
-from gcloud.aio.pubsub import PublisherClient, SubscriberClient, SubscriberMessage
+import aiohttp
+from gcloud.aio.pubsub import subscribe, PublisherClient, SubscriberClient, SubscriberMessage
+from google.cloud import pubsub_v1
 from yapic import json
 
 from cryptofeed import FeedHandler
@@ -27,7 +28,7 @@
 $ gcloud beta emulators pubsub start --host-port=0.0.0.0:8681
 
 3. In another console, run the demo
-$ export PUBSUB_EMULATOR_HOST='0.0.0.0:8681' python examples/demo_gcppubsub.py
+$ export PUBSUB_EMULATOR_HOST='0.0.0.0:8681'; python examples/demo_gcppubsub.py
 
 
 Try it with GCP Pub/Sub in the cloud
@@ -45,51 +46,46 @@
 
 
 async def message_callback(message: SubscriberMessage) -> None:
-    try:
-        data = json.loads(message.data)
-    except Exception:
-        message.nack()
-    else:
-        print(data)
-        message.ack()
+    data = json.loads(message.data)
+    print(data)
 
 
-def start_subscriber(loop, topic):
+async def start_subscriber(topic):
     client = SubscriberClient()
-
-    project_id = os.getenv('GCP_PROJECT')
+    project_id = os.getenv("GCP_PROJECT")
     topic_path = PublisherClient.topic_path(project_id, topic)
     subscription_path = PublisherClient.subscription_path(project_id, topic)
 
     # Create subscription if it doesn't already exist
     try:
-        client.create_subscription(subscription_path, topic_path)
-    except google.api_core.exceptions.PermissionDenied as e:
-        raise TypeError('Please set the GCP_PROJECT environment variable') from e
-
-    # Subscribe to the subscription, receiving a Future that acts as a keepalive
-    keep_alive = client.subscribe(subscription_path, message_callback)
+        await client.create_subscription(subscription_path, topic_path)
+    except aiohttp.client_exceptions.ClientResponseError as e:
+        if e.status == 409:  # Subscription exists
+            pass
+        else:
+            raise TypeError("Please set the GCP_PROJECT environment variable") from e
 
-    # Have the client run forever, pulling messages from this subscription,
-    # passing them to the specified callback function, and wrapping it in an
-    # asyncio task.
-    client.run_forever(keep_alive)
+    # For demo with Pub/Sub emulator, maybe ack_deadline_cache_timeout 300
+    # On GCP, default seems fine.
+    # For more options, check gcloud-aio docs:
+    # https://github.com/talkiq/gcloud-aio/tree/master/pubsub
+    await subscribe(subscription_path, message_callback, client, ack_deadline_cache_timeout=300)
 
 
 def main():
     f = FeedHandler()
 
     trades = TradeGCPPubSub()
-
     cbs = {TRADES: trades}
 
     f.add_feed(Coinbase(channels=[TRADES], symbols=['BTC-USD'], callbacks=cbs))
-
     f.run(start_loop=False)
 
+    # Have the client run forever, pulling messages from subscription_path,
+    # passing them to the specified callback function
     loop = asyncio.get_event_loop()
-
-    start_subscriber(loop, trades.topic)
+    loop.create_task(start_subscriber(trades.topic))
+    loop.run_forever()
 
 
 if __name__ == '__main__':

setup.py

@@ -75,7 +75,7 @@ def run_tests(self):
     ],
     extras_require={
         "arctic": ["arctic"],
-        "gcp_pubsub": ["google_cloud_pubsub", "gcloud_aio_pubsub"],
+        "gcp_pubsub": ["google_cloud_pubsub~=2.2.0", "gcloud_aio_pubsub"],
         "kafka": ["aiokafka>=0.7.0"],
         "mongo": ["motor"],
         "postgres": ["asyncpg"],