How to Manage Google API Errors in Python

Question

I'm currently doing a lot of stuff with BigQuery, and am using a lot of try... except.... It looks like just about every error I get back from BigQuery is a apiclient.errors.HttpError, but with different strings attached to them, i.e.:

<HttpError 409 when requesting https://www.googleapis.com/bigquery/v2/projects/some_id/datasets/some_dataset/tables?alt=json returned "Already Exists: Table some_id:some_dataset.some_table">

<HttpError 404 when requesting https://www.googleapis.com/bigquery/v2/projects/some_id/jobs/sdfgsdfg?alt=json returned "Not Found: Job some_id:sdfgsdfg">

among many others. Right now the only way I see to handle these is to run regexs on the error messages, but this is messy and definitely not ideal. Is there a better way?

Answer 1

BigQuery is a REST API, the errors it uses follow standard HTTP error conventions.

In python, an HttpError has a resp.status field that returns the HTTP status code. As you show above, 409 is 'conflict', 404 is 'not found'.

For example:

from googleapiclient.errors import HttpError
try:
   ...
except HttpError as err:
  # If the error is a rate limit or connection error,
  # wait and try again.
  if err.resp.status in [403, 500, 503]:
    time.sleep(5)
  else: raise

The response is also a json object, an even better way is to parse the json and read the error reason field:

if err.resp.get('content-type', '').startswith('application/json'):
    reason = json.loads(err.content).get('error').get('errors')[0].get('reason')

This can be: notFound, duplicate, accessDenied, invalidQuery, backendError, resourcesExceeded, invalid, quotaExceeded, rateLimitExceeded, timeout, etc.