Closing consumer multiple times should not raise RunTimeError

[mkmoisen]

The current behavior is to raise a RunTimeError if consumer.close is called more than once.

This proposed change makes close rerunnable by not raising RunTimeError if it is called more than once.

This will make it convenient for developers to safely call consumer.close in a finally or a context manager without having to trap this exception.

The use case is to make close rerunnable, for example if you wanted to make a context manager, or if you had a large function wrapped in a try/except/finally. Another programmer who calls your context manager can close inside if he wants; otherwise the context manager will close for him.

import contextlib
from confluent_kafka import Consumer

@contextlib.contextmanager
def kafka():
    consumer = Consumer({...})
    try:
        yield consumer
    finally:
        # currently, would need to wrap this in a try/except
        consumer.close()

# ...
# Some programmers may want to call close explicitly
with kafka() as consumer:
        # do something
        consumer.close()

# Other programmers would prefer the context manager to take care
with kafka() as consumer:
    # do something

I'm also under the impression that the majority of the other python libraries that close resources also make close rerunnable. I think it would be a good idea to have confluent_kafka follow this pattern.

from requests import Session
s = Session()
s.close()
s.close()  # does not raise an exception

import sqlite3
conn = sqlite3.connect(':memory:')
conn.close()
conn.close()  # does not raise an exception

[ghost]

@confluentinc It looks like @mkmoisen just signed our Contributor License Agreement. 👍

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clabot