Question about error call backs about librdkafka HOT 6 CLOSED

That sounds like a reasonable thing, I will add it to the library.
Thanks.

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Much appreciated. Note I just started with librdkafka, so expect more
questions and bug reports from me :)

On Fri, Dec 27, 2013 at 6:21 AM, Magnus Edenhill
[email protected]:

That sounds like a reasonable thing, I will add it to the library.
Thanks.

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I've verified that this already works as intended, but you need to call rd_kafka_poll() at regular intervals to let it call your error callback -(error_cb).

It will call the error callback with err set to RD_KAFKA_RESP_ERR__RESOLVE.

I.e.:
ERROR CALLBACK: rdkafka#consumer-0: Local: Host resolution failure: Failed to resolve 'false.edenhill.se:9092': Name or service not known

You can verify this behaviour with rdkafka_performance:
./rdkafka_performance -C -t topic -p 0 -b bad.host.name -I

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Added a rd_kafka_poll() immediately after rd_kafka_brokers_add() and it worked perfectly. thanks! (Note, I had to do a poll with a timeout rather than -1 because when the broker list is good, the poll hangs. Not sure if this is expected or not).

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The RESOLVE error callback will be triggered when the resolve fails, and depending on DNS configuration, network latency, resolver cache, etc, this may be anything from 1ms to 5 minutes, it really depends on the system setup.

Doing a poll(-1) means to wait forever, which is not what you want, and you cant really use a predefined timeout either for the above reasons.

I suggest that your application should assume that the provided brokers are correct, and if they are not and an error callback for RESOLVE is triggered, you handle the problem there, even if it is a bit late.

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If you need to check that the brokers resolve you could resolve them yourself and provide them with numerical ip address to rd_kafka_brokers_add() or "metadata.broker.list" config property.

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