310 lines
15 KiB
Plaintext
310 lines
15 KiB
Plaintext
[[modules-snapshots]]
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== Snapshot And Restore
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The snapshot and restore module allows to create snapshots of individual indices or an entire cluster into a remote
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repository. At the time of the initial release only shared file system repository was supported, but now a range of
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backends are available via officially supported repository plugins.
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[float]
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=== Repositories
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Before any snapshot or restore operation can be performed a snapshot repository should be registered in
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Elasticsearch. The following command registers a shared file system repository with the name `my_backup` that
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will use location `/mount/backups/my_backup` to store snapshots.
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[source,js]
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-----------------------------------
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$ curl -XPUT 'http://localhost:9200/_snapshot/my_backup' -d '{
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"type": "fs",
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"settings": {
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"location": "/mount/backups/my_backup",
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"compress": true
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}
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}'
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-----------------------------------
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Once repository is registered, its information can be obtained using the following command:
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[source,js]
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-----------------------------------
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$ curl -XGET 'http://localhost:9200/_snapshot/my_backup?pretty'
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-----------------------------------
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[source,js]
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-----------------------------------
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{
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"my_backup" : {
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"type" : "fs",
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"settings" : {
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"compress" : "true",
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"location" : "/mount/backups/my_backup"
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}
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}
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}
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-----------------------------------
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If a repository name is not specified, or `_all` is used as repository name Elasticsearch will return information about
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all repositories currently registered in the cluster:
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[source,js]
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-----------------------------------
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$ curl -XGET 'http://localhost:9200/_snapshot'
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-----------------------------------
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or
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[source,js]
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-----------------------------------
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$ curl -XGET 'http://localhost:9200/_snapshot/_all'
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-----------------------------------
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[float]
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===== Shared File System Repository
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The shared file system repository (`"type": "fs"`) is using shared file system to store snapshot. The path
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specified in the `location` parameter should point to the same location in the shared filesystem and be accessible
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on all data and master nodes. The following settings are supported:
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[horizontal]
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`location`:: Location of the snapshots. Mandatory.
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`compress`:: Turns on compression of the snapshot files. Defaults to `true`.
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`chunk_size`:: Big files can be broken down into chunks during snapshotting if needed. The chunk size can be specified in bytes or by
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using size value notation, i.e. 1g, 10m, 5k. Defaults to `null` (unlimited chunk size).
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`max_restore_bytes_per_sec`:: Throttles per node restore rate. Defaults to `20mb` per second.
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`max_snapshot_bytes_per_sec`:: Throttles per node snapshot rate. Defaults to `20mb` per second.
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[float]
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===== Read-only URL Repository
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The URL repository (`"type": "url"`) can be used as an alternative read-only way to access data created by shared file
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system repository is using shared file system to store snapshot. The URL specified in the `url` parameter should
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point to the root of the shared filesystem repository. The following settings are supported:
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[horizontal]
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`url`:: Location of the snapshots. Mandatory.
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[float]
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===== Repository plugins
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Other repository backends are available in these official plugins:
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* https://github.com/elasticsearch/elasticsearch-cloud-aws#s3-repository[AWS Cloud Plugin] for S3 repositories
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* https://github.com/elasticsearch/elasticsearch-hadoop/tree/master/repository-hdfs[HDFS Plugin] for Hadoop environments
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* https://github.com/elasticsearch/elasticsearch-cloud-azure#azure-repository[Azure Cloud Plugin] for Azure storage repositories
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[float]
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=== Snapshot
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A repository can contain multiple snapshots of the same cluster. Snapshot are identified by unique names within the
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cluster. A snapshot with the name `snapshot_1` in the repository `my_backup` can be created by executing the following
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command:
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[source,js]
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-----------------------------------
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$ curl -XPUT "localhost:9200/_snapshot/my_backup/snapshot_1?wait_for_completion=true"
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-----------------------------------
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The `wait_for_completion` parameter specifies whether or not the request should return immediately or wait for snapshot
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completion. By default snapshot of all open and started indices in the cluster is created. This behavior can be changed
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by specifying the list of indices in the body of the snapshot request.
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[source,js]
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-----------------------------------
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$ curl -XPUT "localhost:9200/_snapshot/my_backup/snapshot_1" -d '{
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"indices": "index_1,index_2",
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"ignore_unavailable": "true",
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"include_global_state": false
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}'
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-----------------------------------
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The list of indices that should be included into the snapshot can be specified using the `indices` parameter that
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supports <<search-multi-index-type,multi index syntax>>. The snapshot request also supports the
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`ignore_unavailable` option. Setting it to `true` will cause indices that do not exist to be ignored during snapshot
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creation. By default, when `ignore_unavailable` option is not set and an index is missing the snapshot request will fail.
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By setting `include_global_state` to false it's possible to prevent the cluster global state to be stored as part of
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the snapshot. By default, entire snapshot will fail if one or more indices participating in the snapshot don't have
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all primary shards available. This behaviour can be changed by setting `partial` to `true`.
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The index snapshot process is incremental. In the process of making the index snapshot Elasticsearch analyses
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the list of the index files that are already stored in the repository and copies only files that were created or
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changed since the last snapshot. That allows multiple snapshots to be preserved in the repository in a compact form.
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Snapshotting process is executed in non-blocking fashion. All indexing and searching operation can continue to be
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executed against the index that is being snapshotted. However, a snapshot represents the point-in-time view of the index
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at the moment when snapshot was created, so no records that were added to the index after snapshot process had started
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will be present in the snapshot. The snapshot process starts immediately for the primary shards that has been started
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and are not relocating at the moment. Before version 1.2.0, the snapshot operation fails if the cluster has any relocating or
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initializing primaries of indices participating in the snapshot. Starting with version 1.2.0, Elasticsearch waits for
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relocation or initialization of shards to complete before snapshotting them.
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Besides creating a copy of each index the snapshot process can also store global cluster metadata, which includes persistent
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cluster settings and templates. The transient settings and registered snapshot repositories are not stored as part of
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the snapshot.
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Only one snapshot process can be executed in the cluster at any time. While snapshot of a particular shard is being
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created this shard cannot be moved to another node, which can interfere with rebalancing process and allocation
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filtering. Once snapshot of the shard is finished Elasticsearch will be able to move shard to another node according
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to the current allocation filtering settings and rebalancing algorithm.
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Once a snapshot is created information about this snapshot can be obtained using the following command:
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[source,shell]
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-----------------------------------
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$ curl -XGET "localhost:9200/_snapshot/my_backup/snapshot_1"
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-----------------------------------
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All snapshots currently stored in the repository can be listed using the following command:
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[source,shell]
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-----------------------------------
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$ curl -XGET "localhost:9200/_snapshot/my_backup/_all"
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-----------------------------------
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A snapshot can be deleted from the repository using the following command:
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[source,shell]
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-----------------------------------
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$ curl -XDELETE "localhost:9200/_snapshot/my_backup/snapshot_1"
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-----------------------------------
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When a snapshot is deleted from a repository, Elasticsearch deletes all files that are associated with the deleted
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snapshot and not used by any other snapshots. If the deleted snapshot operation is executed while the snapshot is being
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created the snapshotting process will be aborted and all files created as part of the snapshotting process will be
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cleaned. Therefore, the delete snapshot operation can be used to cancel long running snapshot operations that were
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started by mistake.
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[float]
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=== Restore
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A snapshot can be restored using the following command:
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[source,shell]
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-----------------------------------
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$ curl -XPOST "localhost:9200/_snapshot/my_backup/snapshot_1/_restore"
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-----------------------------------
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By default, all indices in the snapshot as well as cluster state are restored. It's possible to select indices that
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should be restored as well as prevent global cluster state from being restored by using `indices` and
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`include_global_state` options in the restore request body. The list of indices supports
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<<search-multi-index-type,multi index syntax>>. The `rename_pattern` and `rename_replacement` options can be also used to
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rename index on restore using regular expression that supports referencing the original text as explained
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http://docs.oracle.com/javase/6/docs/api/java/util/regex/Matcher.html#appendReplacement(java.lang.StringBuffer,%20java.lang.String)[here].
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Set `include_aliases` to `false` to prevent aliases from being restored together with associated indices coming[1.3.0].
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[source,js]
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-----------------------------------
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$ curl -XPOST "localhost:9200/_snapshot/my_backup/snapshot_1/_restore" -d '{
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"indices": "index_1,index_2",
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"ignore_unavailable": "true",
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"include_global_state": false,
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"rename_pattern": "index_(.+)",
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"rename_replacement": "restored_index_$1"
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}'
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-----------------------------------
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The restore operation can be performed on a functioning cluster. However, an existing index can be only restored if it's
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closed. The restore operation automatically opens restored indices if they were closed and creates new indices if they
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didn't exist in the cluster. If cluster state is restored, the restored templates that don't currently exist in the
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cluster are added and existing templates with the same name are replaced by the restored templates. The restored
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persistent settings are added to the existing persistent settings.
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[float]
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=== Partial restore
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coming[1.3.0]
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By default, entire restore operation will fail if one or more indices participating in the operation don't have
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snapshots of all shards available. It can occur if some shards failed to snapshot for example. It is still possible to
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restore such indices by setting `partial` to `true`. Please note, that only successfully snapshotted shards will be
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restored in this case and all missing shards will be recreated empty.
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[float]
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=== Snapshot status
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added[1.1.0]
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A list of currently running snapshots with their detailed status information can be obtained using the following command:
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[source,shell]
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-----------------------------------
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$ curl -XGET "localhost:9200/_snapshot/_status"
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-----------------------------------
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In this format, the command will return information about all currently running snapshots. By specifying a repository name, it's possible
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to limit the results to a particular repository:
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[source,shell]
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-----------------------------------
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$ curl -XGET "localhost:9200/_snapshot/my_backup/_status"
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-----------------------------------
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If both repository name and snapshot id are specified, this command will return detailed status information for the given snapshot even
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if it's not currently running:
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[source,shell]
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-----------------------------------
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$ curl -XGET "localhost:9200/_snapshot/my_backup/snapshot_1/_status"
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-----------------------------------
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Multiple ids are also supported:
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[source,shell]
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-----------------------------------
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$ curl -XGET "localhost:9200/_snapshot/my_backup/snapshot_1,snapshot_2/_status"
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-----------------------------------
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[float]
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=== Monitoring snapshot/restore progress
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There are several ways to monitor the progress of the snapshot and restores processes while they are running. Both
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operations support `wait_for_completion` parameter that would block client until the operation is completed. This is
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the simplest method that can be used to get notified about operation completion.
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The snapshot operation can be also monitored by periodic calls to the snapshot info:
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[source,shell]
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-----------------------------------
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$ curl -XGET "localhost:9200/_snapshot/my_backup/snapshot_1"
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-----------------------------------
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Please note that snapshot info operation is using the same resources and thread pool as the snapshot operation. So,
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executing snapshot info operation while large shards are being snapshotted can cause the snapshot info operation to wait
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for available resources before returning the result. On very large shards the wait time can be significant.
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To get more immediate and complete information about snapshots the snapshot status command can be used instead:
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[source,shell]
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-----------------------------------
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$ curl -XGET "localhost:9200/_snapshot/my_backup/snapshot_1/_status"
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-----------------------------------
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While snapshot info method returns only basic information about the snapshot in progress, the snapshot status returns
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complete breakdown of the current state for each shard participating in the snapshot.
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The restore process piggybacks on the standard recovery mechanism of the Elasticsearch. As a result, standard recovery
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monitoring services can be used to monitor the state of restore. When restore operation is executed the cluster
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typically goes into `red` state. It happens because the restore operation starts with "recovering" primary shards of the
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restored indices. During this operation the primary shards become unavailable which manifests itself in the `red` cluster
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state. Once recovery of primary shards is completed Elasticsearch is switching to standard replication process that
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creates the required number of replicas at this moment cluster switches to the `yellow` state. Once all required replicas
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are created, the cluster switches to the `green` states.
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The cluster health operation provides only a high level status of the restore process. It’s possible to get more
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detailed insight into the current state of the recovery process by using <<indices-recovery, indices recovery>> and
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<<cat-recovery, cat recovery>> APIs.
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[float]
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=== Stopping currently running snapshot and restore operations
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The snapshot and restore framework allows running only one snapshot or one restore operation at time. If currently
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running snapshot was executed by mistake or takes unusually long, it can be terminated using snapshot delete operation.
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The snapshot delete operation checks if deleted snapshot is currently running and if it does, the delete operation stops
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such snapshot before deleting the snapshot data from the repository.
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The restore operation is using standard shard recovery mechanism. Therefore, any currently running restore operation can
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be canceled by deleting indices that are being restored. Please note that data for all deleted indices will be removed
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from the cluster as a result of this operation.
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