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