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Adds add_callback/add_errback example to docs #1441

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Mar 29, 2018
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Adds add_callback/add_errback example to docs #1441

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0f89ee9
Adds add_callback/add_errback example to docs
Berkodev Mar 13, 2018
ba33bb8
Fixes errback example in docs
Berkodev Mar 29, 2018
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12 changes: 12 additions & 0 deletions docs/usage.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,18 @@ KafkaProducer
for _ in range(100):
producer.send('my-topic', b'msg')

def on_send_success(record_metadata):
print(record_metadata.topic)
print(record_metadata.partition)
print(record_metadata.offset)

def on_send_error(excp):
log.exception()
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Just doublechecking, since I'm not sure how this works:
Is the send exception always going to be the most recent one raised? If you screwed up your callback somehow and threw an exception, it would hide the send exception.

Perhaps it'd be better to illustrate how to pass the excp into log.error()? This is honestly less of a kafka-python thing, and more just showing clearly how python logging works, as we often get questions on the issue tracker about that as well...

Just a thought, I do not have a strong opinion, and I am not even 100% sure how this works in this particular example as I haven't played with it...

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I agree -- log.exception() may not always work here because we don't guarantee that the errback is evaluated within the context of a exception handler. It would be better to pass the exception explicitly:

def on_send_error(excp):
    log.error('I am an errback', exc_info=excp)

# handle exception

# produce asynchronously with callbacks
producer.send('my-topic', b'raw_bytes').add_callback(on_send_success).add_errback(on_send_error)

# block until all async messages are sent
producer.flush()

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