Upgrading

Elasticsearch can usually be upgraded using a rolling upgrade process, resulting in no interruption of service. This section details how to perform both rolling and restart upgrades. To determine whether a rolling upgrade is supported for your release, please consult this table:

Before performing an upgrade, it’s a good idea to back up the data on your system. This will allow you to roll back in the event of a problem with the upgrade. The upgrades sometimes include upgrades to the Lucene libraries used by Elasticsearch to access the index files, and after an index file has been updated to work with a new version of Lucene, it may not be accessible to the versions of Lucene present in earlier Elasticsearch releases.

To back up a running 0.90.x system, first disable index flushing. This will prevent indices from being flushed to disk while the backup is in process:

$ curl -XPUT 'http://localhost:9200/_all/_settings' -d '{
    "index": {
        "translog.disable_flush": "true"
    }
}'

Then disable reallocation. This will prevent the cluster from moving data files from one node to another while the backup is in process:

$ curl -XPUT 'http://localhost:9200/_cluster/settings' -d '{
    "transient" : {
        "cluster.routing.allocation.disable_allocation": "true"
    }
}'

After reallocation and index flushing are disabled, initiate a backup of Elasticsearch’s data path using your favorite backup method (tar, storage array snapshots, backup software). When the backup is complete and data no longer needs to be read from the Elasticsearch data path, reallocation and index flushing must be re-enabled:

$ curl -XPUT 'http://localhost:9200/_all/_settings' -d '{
    "index": {
        "translog.disable_flush": "false"
    }
}'

$ curl -XPUT 'http://localhost:9200/_cluster/settings' -d '{
    "transient" : {
        "cluster.routing.allocation.disable_allocation": "false"
    }
}'

To back up a running 1.0 or later system, it is simplest to use the snapshot feature. See the complete instructions for backup and restore with snapshots.

A rolling upgrade allows the ES cluster to be upgraded one node at a time, with no observable downtime for end users. Running multiple versions of Elasticsearch in the same cluster for any length of time beyond that required for an upgrade is not supported, as shard replication from the more recent version to the previous versions will not work.

Within minor or maintenance releases after release 1.0, rolling upgrades are supported. To perform a rolling upgrade:

This syntax applies to Elasticsearch 1.0 and later:

        curl -XPUT localhost:9200/_cluster/settings -d '{
                "transient" : {
                    "cluster.routing.allocation.enable" : "none"
                }
        }'

curl -XPOST 'http://localhost:9200/_cluster/nodes/_local/_shutdown'

        curl -XPUT localhost:9200/_cluster/settings -d '{
                "transient" : {
                    "cluster.routing.allocation.enable" : "all"
                }
        }'

It may be possible to perform the upgrade by installing the new software while the service is running. This would reduce downtime by ensuring the service was ready to run on the new version as soon as it is stopped on the node being upgraded. This can be done by installing the new version in its own directory and using the symbolic link method outlined above. It is important to test this procedure first to be sure that site-specific configuration data and production indices will not be overwritten during the upgrade process.

Elasticsearch releases prior to 1.0 and releases after 1.0 are not compatible with each other, so a rolling upgrade is not possible. In order to upgrade a pre-1.0 system to 1.0 or later, a full cluster stop and start is required. In order to perform this upgrade:

This syntax is from versions prior to 1.0:

	curl -XPUT localhost:9200/_cluster/settings -d '{
		"persistent" : {
		"cluster.routing.allocation.disable_allocation" : true
		}
	}'

	curl -XPOST 'http://localhost:9200/_shutdown'

This syntax is from release 1.0 and later:

	curl -XPUT localhost:9200/_cluster/settings -d '{
     		"persistent" : {
		"cluster.routing.allocation.disable_allocation": false,
         	"cluster.routing.allocation.enable" : "all"
     		}
 	}'

The cluster upgrade can be streamlined by installing the software before stopping cluster services. If this is done, testing must be performed to ensure that no production data or configuration files are overwritten prior to restart.