fix: add ConnectionError to default retry

[cojenco]

This adds python built-in ConnectionError to default retryable types.
ConnectionError was recently added in the BigQuery library to allow retries.

Fixes #426 🦕

[tritone]

thanks!

[tritone]

ConnectionError has a bunch of subclasses: https://docs.python.org/3/library/exceptions.html#ConnectionError . Just wanted to confirm that we consider all of these retryable?

Also, is there a test where we should add this as a test case?

[tseaver]

One or more tests should be added to the Test_should_retry class in tests/unit/test_retry.py (see the BigQuery PR for examples).

Also, that PR makes requests.exceptions.ConnectionError an explicit retryable type. The requests version does not derive from the stdlib type:

$ .nox/unit-3-9/bin/python
Python 3.9.0 (default, Apr 20 2021, 11:50:03) 
[GCC 9.3.0] on linux
>>> import requests.exceptions
>>> requests.exceptions.ConnectionError
<class 'requests.exceptions.ConnectionError'>
>>> requests.exceptions.ConnectionError.__mro__
(<class 'requests.exceptions.ConnectionError'>, <class 'requests.exceptions.RequestException'>, <class 'OSError'>, <class 'Exception'>, <class 'BaseException'>, <class 'object'>)

[tseaver]

Note that ConnectionError is not a stdlib type in Python 2.7:

$ .nox/unit-2-7/bin/python
Python 2.7.17 (default, Apr 20 2021, 14:27:04) 
[GCC 9.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> ConnectionError
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'ConnectionError' is not defined

We need to do something like:

try:
    _RETRYABLE_STDLIB_TYPES = {ConnectionError,)
except NameError:
    _RETRYABLE_STDLIB_TYPES = {}

and then, below:

RETRYABLE_TYPES = _RETRYABLE_STDLIB_TYPES + (
    api_exceptions.TooManyRequests,  # 429
    ...
)

[cojenco]

@tritone @tseaver Thanks for reviewing! Looking at the python3 docs and previous discussion in the Big Query, ConnectionError and its subclasses are retryable. From users feedback, this error occurs when there are multiple Cloud Functions running and/or subsequent reinvocation of Cloud Functions. The retry test is set up with a loop that tests each default retry. I'll double check to make the changes and add one or more specific tests. Thanks!

[cojenco]

@tseaver I noticed that ConnectionError is not a stdlib type in Python 2.7 upon submission. Changed PR to draft to implement changes. This is exactly what I need. Thanks so much for the pointers!

[tseaver]

One or more tests should be added to the Test_should_retry class in tests/unit/test_retry.py (see the BigQuery PR for examples).

Also, that PR makes requests.exceptions.ConnectionError an explicit retryable type. The requests version does not derive from the stdlib type:

$ .nox/unit-3-9/bin/python
Python 3.9.0 (default, Apr 20 2021, 11:50:03) 
[GCC 9.3.0] on linux
>>> import requests.exceptions
>>> requests.exceptions.ConnectionError
<class 'requests.exceptions.ConnectionError'>
>>> requests.exceptions.ConnectionError.__mro__
(<class 'requests.exceptions.ConnectionError'>, <class 'requests.exceptions.RequestException'>, <class 'OSError'>, <class 'Exception'>, <class 'BaseException'>, <class 'object'>)

[tseaver]

Note that ConnectionError is not a stdlib type in Python 2.7:

$ .nox/unit-2-7/bin/python
Python 2.7.17 (default, Apr 20 2021, 14:27:04) 
[GCC 9.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> ConnectionError
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'ConnectionError' is not defined

We need to do something like:

try:
    _RETRYABLE_STDLIB_TYPES = {ConnectionError,)
except NameError:
    _RETRYABLE_STDLIB_TYPES = {}

and then, below:

RETRYABLE_TYPES = _RETRYABLE_STDLIB_TYPES + (
    api_exceptions.TooManyRequests,  # 429
    ...
)

[google-cla]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for all the commit author(s) or Co-authors. If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.
In order to pass this check, please resolve this problem and then comment @googlebot I fixed it.. If the bot doesn't comment, it means it doesn't think anything has changed.

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[google-cla]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for all the commit author(s) or Co-authors. If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.
In order to pass this check, please resolve this problem and then comment @googlebot I fixed it.. If the bot doesn't comment, it means it doesn't think anything has changed.

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[tseaver]

@googlebot I fixed it.

[google-cla]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for all the commit author(s) or Co-authors. If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.
In order to pass this check, please resolve this problem and then comment @googlebot I fixed it.. If the bot doesn't comment, it means it doesn't think anything has changed.

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[cojenco]

@googlebot I fixed it.

[google-cla]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for all the commit author(s) or Co-authors. If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.
In order to pass this check, please resolve this problem and then comment @googlebot I fixed it.. If the bot doesn't comment, it means it doesn't think anything has changed.

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[tseaver]

@cojenco I don't know what the CLAbot is on about. As a Googler, I believe you can manually clear the cla: no label and set cla: yes instead.

[cojenco]

Thanks @tseaver! Manually added the cla label. I'm looking at my configs. So when I commited the suggestion directly on Github, the email logged was a <users.noreply.github.com> account.

[tseaver]

Ugh, I tested that syntax at the Python command prompt, where __buitins__ is a module. Per the Python docs for the builtins module, we should probably not rely on it being either the module or its dict, and instead move to something like:

try:
    ConnectionError
except NameError:
    _HAS_CONNECTION_ERROR = False
else:
    _HAS_CONNECTION_ERROR = True

and then use that flag to control the skip:

    @unittest.skipUnless(_HAS_CONNECTION_ERROR, "...")

Since my suggestion didn't work out, and messed up the CLAbot, maybe it would be best to rebase away
bcfe2be and start fresh.