Anatoly Fayngelerin created KAFKA-1082:
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Summary: zkclient dies after UnknownHostException in zk reconnect
Key: KAFKA-1082
URL: https://issues.apache.org/jira/browse/KAFKA-1082
Project: Kafka
Issue Type: Bug
Components: core
Affects Versions: 0.8, 0.7.2
Reporter: Anatoly Fayngelerin
Moving this here from the dev list:
I've run into the following issue with the Kafka server. The zkclient lib seems
to die silently if there is an UnknownHostException(or any IOException) while
reconnecting the ZK session. I've filed a bug about this with the zkclient
lib(https://github.com/sgroschupf/zkclient/issues/23). The ramifications for
Kafka were the silent loss of all ephemeral nodes associated with the affected
process.
It is fairly easy to reproduce this locally using the following steps:
-- Configure a local kafka broker to connect to a local ZK instance using a DNS
alias(e.g. add "127.0.0.1 kafka-test-dns" to your /etc/hosts)
-- Start the broker, observe that ephemeral nodes have been added to ZK
-- Suspend the broker process, preventing it from sending heartbeats to the ZK
instance. Observe the loss of ephemeral nodes in ZK.
-- Remove the DNS alias(e.g. comment out the /etc/hosts line).
-- Upon resuming the broker, the UknownHostException is logged. After this
point, the server cannot re-establish its ZK connection. Re-enabling the alias,
for example, does not resume normal operation. The broker continues accepting
requests, without participating in the ZK protocols.
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