While running integration tests for Sarama (the go client) we came across a pattern of connection losses that reliably puts kafka into a bad state: several of the brokers start spinning, chewing ~30% CPU and spamming the logs with hundreds of thousands of lines like:
This can be easily and reliably reproduced using the toxiproxy-final branch of https://github.com/Shopify/sarama which includes a vagrant script for provisioning the appropriate cluster:
- git clone https://github.com/Shopify/sarama.git
- git checkout test-jira-kafka-2082
- vagrant up
- TEST_SEED=1427917826425719059 DEBUG=true go test -v
After the test finishes (it fails because the cluster ends up in a bad state), you can log into the cluster machine with vagrant ssh and inspect the bad nodes. The vagrant script provisions five zookeepers and five brokers in /opt/kafka-9091/ through /opt/kafka-9095/.
Additional context: the test produces continually to the cluster while randomly cutting and restoring zookeeper connections (all connections to zookeeper are run through a simple proxy on the same vm to make this easy). The majority of the time this works very well and does a good job exercising our producer's retry and failover code. However, under certain patterns of connection loss (the TEST_SEED in the instructions is important), kafka gets confused. The test never cuts more than two connections at a time, so zookeeper should always have quorum, and the topic (with three replicas) should always be writable.
Completely restarting the cluster via vagrant reload seems to put it back into a sane state.