332 lines
16 KiB
Plaintext
332 lines
16 KiB
Plaintext
[[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"`) is using shared file system to store snapshot. 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 shared file
|
||
system repository is using shared file system to store snapshot. 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 <<search-multi-index-type,multi index syntax>>. 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
|
||
<<search-multi-index-type,multi index syntax>>. 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
|
||
<<indices-open-close,closed>>. 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 is using the same resources and thread pool as the snapshot operation. So,
|
||
executing 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 <<indices-recovery, indices recovery>> and
|
||
<<cat-recovery, cat recovery>> 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 is using 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.
|
||
|
||
|