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Service restarts

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Revision as of 15:53, 24 November 2015 by imported>Muehlenhoff (Add preliminary notes for hadoop)
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This page collects procedures to restart services (or reboot the underlying server) in the WMF production cluster.

Hadoop workers

Three of the hadoop workers run an additional JournalNode process. These are configured in the puppet manifest:

  • The other Hadoop workers are running two services (hadoop-hdfs-datanode and hadoop-yarn-nodemanager). The services on the Hadoop workers can be restarted in arbitrary orde. The service restarts have no user-visible impact (and the machines can also be rebooted).
  • TODO: Add notes for JournalNode hosts

Kafka brokers

One Kafka broker can be restarted/rebooted at a time. It needs to be ensured that all replicas arefully replicated. After restarting a broker a replica election should be performed.


We run four ntpd servers (chromium, hydrogen, acamar, achenar) and all of these are configured for use by the other servers in the cluster. As such, as long as only one server is restarted/rebooted at at time, everything is fine. The ntpd running locally on the individual servers can easily be restarted at any any time.