Frequently Asked Questions

General

Is Sarama used in production anywhere?

Yes. At the time of writing (March, 2017) Shopify uses Sarama heavily. I understand that there are other major companies using it in production too. If you work for such a company and file a ticket to let me know, I'll list it here.

How do I fetch an offset for a specific timestamp?

Use Client.GetOffset().

Starting in Sarama v1.11.0, this method will automatically use Kafka's new precise timestamp lookup if your Kafka version (as provided by Config.Version) is at least 0.10.1. Otherwise, the method will fall back to the old API which returns only a very approximate value.

Consuming

How can I use Sarama to join a consumer group?

Consumer-groups are complicated, so this logic lives in a separate (unaffiliated) project which builds on top of Sarama. For Kafka-based tracking (Kafka 0.9 and later), use https://github.com/bsm/sarama-cluster. For Zookeeper-based tracking (Kafka 0.8.2 and earlier), use https://github.com/wvanbergen/kafka.

For issues with these libraries, please file a ticket in their respective repositories, not with Sarama.

Why am I getting a nil message from the Sarama consumer?

Sarama will never put a nil message on the channel. If you are getting nils then the channel has been closed (a receive from a closed channel returns the zero value for that type, which is nil for pointers).

The channel will normally be closed only when the PartitionConsumer has been shut down, either by calling Close or AsyncClose on it. However, the PartitionConsumer may sometimes shut itself down when it encounters an unrecoverable error; in this case you will get an appropriate error on the Errors channel, and it will also log a message to sarama.Logger that looks something like: consumer/TOPIC/PARTITION shutting down because REASON.

How do I consume until the end of a partition?

You don't. Kafka doesn't have the concept of a topic or partition "ending"; it was designed for systems where new messages are constantly arriving and so the question is meaningless. There are, however, a few ways to approximate this, both with some obvious drawbacks:

• Wait for the configured Consumer.MaxWaitTime time to pass, and if no messages have arrived within that time then assume you're done.
• Use Client.GetOffset to get the last offset when you start, and consume up until that offset is reached.

Producing

How fast is Sarama's producer?

Pretty fast, although it depends heavily on your specific configuration, network, hardware, etc. This benchmark is a few years old now but claims to have been able to produce nearly 100k messages per second. If you need a more concrete guarantee for a given scenario, you'll have to run your own benchmark.

Does Sarama's producer guarantee message ordering?

Yes. Like Kafka, Sarama guarantees message order consistency only within a given partition. Order is preserved even when there are network hiccups and certain messages have to be retried.

Does Sarama's producer guarantee that successful messages are contiguous?

No. If five messages (1,2,3,4,5) are fed to the producer in sequence, it is possible (though rare) that the Kafka cluster will end up with messages 1, 2, 4, and 5 in order, but not message 3. In this case you will receive an error for message 3 on the Errors() channel.

Is it safe to send messages to the synchronous producer concurrently from multiple goroutines?

Yes it is, and even encouraged in order to get higher throughput.