151 lines
5.7 KiB
Plaintext
151 lines
5.7 KiB
Plaintext
[[indices-shrink-index]]
|
|
== Shrink Index
|
|
|
|
The shrink index API allows you to shrink an existing index into a new index
|
|
with fewer primary shards. The requested number of primary shards in the target index
|
|
must be a factor of the number of shards in the source index. For example an index with
|
|
`8` primary shards can be shrunk into `4`, `2` or `1` primary shards or an index
|
|
with `15` primary shards can be shrunk into `5`, `3` or `1`. If the number
|
|
of shards in the index is a prime number it can only be shrunk into a single
|
|
primary shard. Before shrinking, a (primary or replica) copy of every shard
|
|
in the index must be present on the same node.
|
|
|
|
Shrinking works as follows:
|
|
|
|
* First, it creates a new target index with the same definition as the source
|
|
index, but with a smaller number of primary shards.
|
|
|
|
* Then it hard-links segments from the source index into the target index. (If
|
|
the file system doesn't support hard-linking, then all segments are copied
|
|
into the new index, which is a much more time consuming process.)
|
|
|
|
* Finally, it recovers the target index as though it were a closed index which
|
|
had just been re-opened.
|
|
|
|
[float]
|
|
=== Preparing an index for shrinking
|
|
|
|
In order to shrink an index, the index must be marked as read-only, and a
|
|
(primary or replica) copy of every shard in the index must be relocated to the
|
|
same node and have <<cluster-health,health>> `green`.
|
|
|
|
These two conditions can be achieved with the following request:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
PUT /my_source_index/_settings
|
|
{
|
|
"settings": {
|
|
"index.routing.allocation.require._name": "shrink_node_name", <1>
|
|
"index.blocks.write": true <2>
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
// CONSOLE
|
|
// TEST[s/^/PUT my_source_index\n/]
|
|
<1> Forces the relocation of a copy of each shard to the node with name
|
|
`shrink_node_name`. See <<shard-allocation-filtering>> for more options.
|
|
|
|
<2> Prevents write operations to this index while still allowing metadata
|
|
changes like deleting the index.
|
|
|
|
It can take a while to relocate the source index. Progress can be tracked
|
|
with the <<cat-recovery,`_cat recovery` API>>, or the <<cluster-health,
|
|
`cluster health` API>> can be used to wait until all shards have relocated
|
|
with the `wait_for_no_relocating_shards` parameter.
|
|
|
|
[float]
|
|
=== Shrinking an index
|
|
|
|
To shrink `my_source_index` into a new index called `my_target_index`, issue
|
|
the following request:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
POST my_source_index/_shrink/my_target_index
|
|
--------------------------------------------------
|
|
// CONSOLE
|
|
// TEST[continued]
|
|
|
|
The above request returns immediately once the target index has been added to
|
|
the cluster state -- it doesn't wait for the shrink operation to start.
|
|
|
|
[IMPORTANT]
|
|
=====================================
|
|
|
|
Indices can only be shrunk if they satisfy the following requirements:
|
|
|
|
* the target index must not exist
|
|
|
|
* The index must have more primary shards than the target index.
|
|
|
|
* The number of primary shards in the target index must be a factor of the
|
|
number of primary shards in the source index. The source index must have
|
|
more primary shards than the target index.
|
|
|
|
* The index must not contain more than `2,147,483,519` documents in total
|
|
across all shards that will be shrunk into a single shard on the target index
|
|
as this is the maximum number of docs that can fit into a single shard.
|
|
|
|
* The node handling the shrink process must have sufficient free disk space to
|
|
accommodate a second copy of the existing index.
|
|
|
|
=====================================
|
|
|
|
The `_shrink` API is similar to the <<indices-create-index, `create index` API>>
|
|
and accepts `settings` and `aliases` parameters for the target index:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
POST my_source_index/_shrink/my_target_index
|
|
{
|
|
"settings": {
|
|
"index.number_of_replicas": 1,
|
|
"index.number_of_shards": 1, <1>
|
|
"index.codec": "best_compression" <2>
|
|
},
|
|
"aliases": {
|
|
"my_search_indices": {}
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
// CONSOLE
|
|
// TEST[s/^/PUT my_source_index\n{"settings": {"index.blocks.write": true}}\n/]
|
|
|
|
<1> The number of shards in the target index. This must be a factor of the
|
|
number of shards in the source index.
|
|
<2> Best compression will only take affect when new writes are made to the
|
|
index, such as when <<indices-forcemerge,force-merging>> the shard to a single
|
|
segment.
|
|
|
|
|
|
NOTE: Mappings may not be specified in the `_shrink` request, and all
|
|
`index.analysis.*` and `index.similarity.*` settings will be overwritten with
|
|
the settings from the source index.
|
|
|
|
[float]
|
|
=== Monitoring the shrink process
|
|
|
|
The shrink process can be monitored with the <<cat-recovery,`_cat recovery`
|
|
API>>, or the <<cluster-health, `cluster health` API>> can be used to wait
|
|
until all primary shards have been allocated by setting the `wait_for_status`
|
|
parameter to `yellow`.
|
|
|
|
The `_shrink` API returns as soon as the target index has been added to the
|
|
cluster state, before any shards have been allocated. At this point, all
|
|
shards are in the state `unassigned`. If, for any reason, the target index
|
|
can't be allocated on the shrink node, its primary shard will remain
|
|
`unassigned` until it can be allocated on that node.
|
|
|
|
Once the primary shard is allocated, it moves to state `initializing`, and the
|
|
shrink process begins. When the shrink operation completes, the shard will
|
|
become `active`. At that point, Elasticsearch will try to allocate any
|
|
replicas and may decide to relocate the primary shard to another node.
|
|
|
|
[float]
|
|
=== Wait For Active Shards
|
|
|
|
Because the shrink operation creates a new index to shrink the shards to,
|
|
the <<create-index-wait-for-active-shards,wait for active shards>> setting
|
|
on index creation applies to the shrink index action as well.
|