Do you have to specify a callback function for the rd_kafka_poll() to work?

[winbatch]

I indicated request.required.acks=1 and am polling in a loop until I get a return value of 1. I have not specified a callback function (I may do this later), but I find that it doesn't ever seem to return 1? Is a callback function required?

In a different program I do have a callback function and it seems to work as expected.

[edenhill]

You will need to set a dr_cb (delivery report callback) and then call rd_kafka_poll() to get indication if a message was delivered or not.

Use rd_kafka_conf_set_dr_cb(), you can look at examples/rdkafka_performance.c for an example.

Even if you dont set a dr_cb, librdkafka will respect your request.required.acks setting and make sure the message does indeed receive the requested number of acks, or else it will retry the transmission.

[winbatch]

I'm pretty sure poll never returns 1 though if no callback is specified
which surprised me

On Friday, December 27, 2013, Magnus Edenhill wrote:

You will need to set a dr_cb (delivery report callback) and then call
rd_kafka_poll() to get indication if a message was delivered or not.

Use rd_kafka_conf_set_dr_cb(), you can look at
examples/rdkafka_performance.c for an example.

Even if you dont set a dr_cb, librdkafka will respect your
request.required.acks setting and make sure the message does indeed receive
the requested number of acks, or else it will retry the transmission.

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[edenhill]

rd_kafka_poll() simply returns the number of internal events served, and not all of them depend on the application having configured a callback.
For instance if no error callback is configured the errors are converted into log messages instead.
So you shouldn't use the return value of rd_kafka_poll() to indicate any sort of produce message success, you need the delivery report callback (dr_cb) for that.