Pub/Sub MergeFrom error publish message

[paulorcf]

🏷 pub/sub
SO: Linux/Ubuntu 16.04
api_core_version = 1.3.0
client_library_version = None
gapic_version = 0.37.2
grpc_version = 1.14.2
python_version = 3.6.4

client = pubsub.PublisherClient.from_service_account_json('account.json')
topic_path = client.topic_path('project_name', 'topic_name')
data = b'The rain in Wales falls mainly on the snails.'
response = client.publish(topic, data)

Version: google-cloud-pubsub==0.37.2

Error:

response = client.publish(topic_path, data) File "venvpy/lib/python3.6/site-packages/google/cloud/pubsub_v1/gapic/publisher_client.py", line 393, in publish messages=messages, TypeError: Parameter to MergeFrom() must be instance of same class: expected google.pubsub.v1.PubsubMessage got int.

[paulorcf]

Seems to be a problem on the pubsub.PublisherClient.from_service_account_json.
I try a different approach using the credentials and works fine!

from google.oauth2 import service_account

credentials = service_account.Credentials.from_service_account_file('account.json')
client = pubsub.PublisherClient(credentials=credentials)

Sorry, but now I don't have a lot of time to debug the "why".

[tseaver]

I don't think there can be any connection between the Client.from_service_account_json factory and the traceback you are reporting. What version of google-cloud-pubsub do you have installed? E.g.:

$ pip show google-cloud-pubsub

[paulorcf]

Version: google-cloud-pubsub==0.37.2

[ericgj]

I just got the same error, google-cloud-pubsub==0.38.0. And the same workaround worked for me too (thanks Paulo). Possibly related StackOverflow question ?

[tseaver]

@paulorcf It looks as though you are bypassing the "main" API for publishing messages (pubsub_v1.PublisherClient.publish), and instead calling the lower-level, GAPIC-generated helper (pubsub_v1.gapic.publisher_client.PublisherClient.publish]), which is definitely not recommended.

The error message you report indicates that one of the items you are passing in data is an int, rather than an instance of google.pubsub.v1.PubsubMessage. Can you show the code in your application which triggers the error?

The recommended path would be:

from google.cloud import pubsub_v1

client = pubsub_v1.PublisherClient()
topic_path = client.topic_path('my-project-123'. 'my-topic-name')
data = b'BYTES OF MESSAGE DATA'

client.publish(topic_path, data, attr='ATTR VALUE')

Please feel free to reopen / follow up if you can show the reproduction case where your app passes values using this pattern.

[ericgj]

I believe they showed their code in the original post, re-pasting it here, it's the same I used. It's the from_service_account_json constructor.

client = pubsub.PublisherClient.from_service_account_json('account.json')
topic_path = client.topic_path('project_name', 'topic_name')
data = b'The rain in Wales falls mainly on the snails.'
response = client.publish(topic, data)

[tseaver]

@ericgj we have passing system test for PublisherClient.publish.

Can you provide the complete traceback, along with the value you are passing to publish?

[paxsonsa]

Working:

from google.cloud import pubsub_v1
from google.oauth2 import service_account

credentials = service_account.Credentials.from_service_account_file('auth.json')
client = pubsub_v1.PublisherClient(credentials=credentials)
topic = client.topic_path('project, 'topic')
client.publish(topic, b'hello')

Not Working:

from google.cloud import pubsub_v1

client = pubsub_v1.PublisherClient.from_service_account_json('auth.json')
topic = client.topic_path('project, 'topic')
client.publish(topic, b'hello')

TRACEBACK:

...
  File ".../python3.6/site-packages/google/cloud/pubsub_v1/gapic/publisher_client.py", line 395, in publish
    messages=messages,
TypeError: Parameter to MergeFrom() must be instance of same class: expected google.pubsub.v1.PubsubMessage got int.

[tseaver]

OK, I can reproduce here. The issue is that pubsub_v1.PublisherClient.from_service_account is returning an instance of the low-level pubsub_v1.gapic.publisher_client.PublisherClient: that class has a different signature for publish.

[tseaver]

@theacodes I believe this is the issue you tried to fix in #5826. Can you shed any light here?

[tseaver]

Looks like #5826 returns a staticmethod, rather than a classmethod, for things that started life as classmethods. That would explain seeing the wrong cls.

[paxsonsa]

Thanks for looking into that and getting that fixed