Page History

...

My consumer seems to have stopped, why?

The high-level consumer will block if

• there are no more messages available
• the next message available is larger than the maximum fetch size you have specified
• your client code simply stops pulling messages from the iterator (the blocking queue will fill up).

First, try to figure out if the consumer has really stopped or is just slow, using our tool

...

If consumer offset is not moving after some time, then consumer is likely to have stopped. If consumer offset is moving, but consumer lag (difference between the end of the log and the consumer offset) is increasing, the consumer is slower than the producer. If the consumer is slow, the typical solution is to increase the degree of parallelism in the consumer. This may require increasing the number of partitions of a topic. If a consumer has stopped, one of the typical causes is that the application code that consumes messages somehow died and therefore killed the consumer thread. We recommend using a try/catch clause to log all Throwable in the consumer logic. Another possibility

The high-level consumer will block if

• there are no more messages available
  • The ConsumerOffsetChecker will show that the log offset of the partitions being consumed does not change on the broker
• the next message available is larger than the maximum fetch size you have specified
  • One possibility of a stalled consumer is that the fetch size in the consumer is smaller than the largest message in the broker. You can use the DumpLogSegments tool to figure out the largest message size and set fetch.size in the consumer config accordingly.
• your client code simply stops pulling messages from the iterator (the blocking queue will fill up).
  • One of the typical causes is that the application code that consumes messages somehow died and therefore killed the consumer thread. We recommend using a try/catch clause to log all Throwable in the consumer logic.

Brokers

How do I choose the number of partitions for a topic?

...