elasticsearch/docs/reference/ccr/remote-recovery.asciidoc

[role="xpack"]
[testenv="platinum"]
[[remote-recovery]]
=== Remote recovery

When you create a follower index, you cannot use it until it is fully initialized.
The _remote recovery_ process builds a new copy of a shard on a follower node by
copying data from the primary shard in the leader cluster. {es} uses this remote
recovery process to bootstrap a follower index using the data from the leader index.
This process provides the follower with a copy of the current state of the leader index,
even if a complete history of changes is not available on the leader due to Lucene
segment merging.

Remote recovery is a network intensive process that transfers all of the Lucene
segment files from the leader cluster to the follower cluster. The follower
requests that a recovery session be initiated on the primary shard in the leader
cluster. The follower then requests file chunks concurrently from the leader. By
default, the process concurrently requests `5` large `1mb` file chunks. This default
behavior is designed to support leader and follower clusters with high network latency
between them.

There are dynamic settings that you can use to rate-limit the transmitted data
and manage the resources consumed by remote recoveries. See
{ref}/ccr-settings.html[{ccr-cap} settings].

You can obtain information about an in-progress remote recovery by using the
{ref}/cat-recovery.html[recovery API] on the follower cluster. Remote recoveries
are implemented using the {ref}/modules-snapshots.html[snapshot and restore] infrastructure. This means that on-going remote recoveries are labelled as type
`snapshot` in the recovery API.