SolrCloud in EC2. Dealing with changing IPs

If you use Amazon EC2 service for a while, you probably aware of the fact that any time you stop/start (reboot) your instance the underlying IP might change. We need to account for that when designing new services in EC2.

Lets see what happens to SolrCloud after IP change:

Note those grayed out IPs. Those are original ones that changed after instance reboot (or crash). There is no harm in keeping old instances (IPs) in the list, but I like to keep my systems clean and real, so I’ll show you the way to remove those from Zookeeper.

Note: The instructions are for Solr 4.7

  1. First we need to download clusterstate.json from Zookeeper ( as you probably already guessed by name, the file stores list of the instances representing our cluster ):/solr/scripts/cloud-scripts/ -zkhost****.net:2181 -cmd get /clusterstate.json > /tmp/clusterstate.json
  2. Next we edit the file and remove node sections matching our orphans IPs.
  3. Clear existing clusterstate.json file from Zookeeper, so we could upload new one:/solr/scripts/cloud-scripts/ -zkhost****:2181 -cmd clear /clusterstate.json
  4. Upload modified version:/solr/scripts/cloud-scripts/ -zkhost****:2181 -cmd putfile /clusterstate.json /tmp/clusterstate.json

Done! At this point your SolrCloud instances list should be clean again.

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