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[DOCS] Separate and reformat synced flush API docs (#46634) (#46839)

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James Rodewig 2019-09-19 08:22:37 -04:00 committed by GitHub
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4
client/rest-high-level/src/main/java/org/elasticsearch/client/IndicesClient.java
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@ -594,7 +594,7 @@ public final class IndicesClient {
/**
* Initiate a synced flush manually using the synced flush API.
* See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-flush.html#synced-flush-api">
* See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-synced-flush-api.html">
* Synced flush API on elastic.co</a>
* @param syncedFlushRequest the request
* @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
@ -608,7 +608,7 @@ public final class IndicesClient {
/**
* Asynchronously initiate a synced flush manually using the synced flush API.
* See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-flush.html#synced-flush-api">
* See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-synced-flush-api.html">
* Synced flush API on elastic.co</a>
* @param syncedFlushRequest the request
* @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized

3
docs/reference/indices.asciidoc
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@ -69,6 +69,7 @@ index settings, aliases, mappings, and index templates.
* <<indices-clearcache>>
* <<indices-refresh>>
* <<indices-flush>>
* <<indices-synced-flush-api>>
* <<indices-forcemerge>>
include::indices/create-index.asciidoc[]
@ -139,6 +140,8 @@ include::indices/clearcache.asciidoc[]
include::indices/flush.asciidoc[]
include::indices/synced-flush.asciidoc[]
include::indices/refresh.asciidoc[]
include::indices/forcemerge.asciidoc[]

198
docs/reference/indices/flush.asciidoc
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@ -60,201 +60,9 @@ POST _flush
--------------------------------------------------
// TEST[s/^/PUT kimchy\nPUT elasticsearch\n/]
[float]
[[synced-flush-api]]
==== Synced Flush
{es} keeps track of which shards have received indexing activity recently, and
considers shards that have not received any indexing operations for 5 minutes to
be inactive. When a shard becomes inactive {es} performs a special kind of flush
known as a _synced flush_. A synced flush performs a normal
<<indices-flush,flush>> on each copy of the shard, and then adds a marker known
as the `sync_id` to each copy to indicate that these copies have identical
Lucene indices. Comparing the `sync_id` markers of the two copies is a very
efficient way to check whether they have identical contents.
When allocating shard copies, {es} must ensure that each replica contains the
same data as the primary. If the shard copies have been synced-flushed and the
replica shares a `sync_id` with the primary then {es} knows that the two copies
have identical contents. This means there is no need to copy any segment files
from the primary to the replica, which saves a good deal of time during
recoveries and restarts.
This is particularly useful for clusters having lots of indices which are very
rarely updated, such as with time-based indices. Without the synced flush
marker, recovery of this kind of cluster would be much slower.
To check whether a shard has a `sync_id` marker or not, look for the `commit`
section of the shard stats returned by the <<indices-stats,indices stats>> API:
[source,console]
--------------------------------------------------
GET twitter/_stats?filter_path=**.commit&level=shards <1>
--------------------------------------------------
// TEST[s/^/PUT twitter\nPOST twitter\/_flush\/synced\n/]
<1> `filter_path` is used to reduce the verbosity of the response, but is entirely optional
which returns something similar to:
[source,console-result]
--------------------------------------------------
{
"indices": {
"twitter": {
"shards": {
"0": [
{
"commit" : {
"id" : "3M3zkw2GHMo2Y4h4/KFKCg==",
"generation" : 3,
"user_data" : {
"translog_uuid" : "hnOG3xFcTDeoI_kvvvOdNA",
"history_uuid" : "XP7KDJGiS1a2fHYiFL5TXQ",
"local_checkpoint" : "-1",
"translog_generation" : "2",
"max_seq_no" : "-1",
"sync_id" : "AVvFY-071siAOuFGEO9P", <1>
"max_unsafe_auto_id_timestamp" : "-1",
"min_retained_seq_no" : "0"
},
"num_docs" : 0
}
}
]
}
}
}
}
--------------------------------------------------
// TESTRESPONSE[s/"id" : "3M3zkw2GHMo2Y4h4\/KFKCg=="/"id": $body.indices.twitter.shards.0.0.commit.id/]
// TESTRESPONSE[s/"translog_uuid" : "hnOG3xFcTDeoI_kvvvOdNA"/"translog_uuid": $body.indices.twitter.shards.0.0.commit.user_data.translog_uuid/]
// TESTRESPONSE[s/"history_uuid" : "XP7KDJGiS1a2fHYiFL5TXQ"/"history_uuid": $body.indices.twitter.shards.0.0.commit.user_data.history_uuid/]
// TESTRESPONSE[s/"sync_id" : "AVvFY-071siAOuFGEO9P"/"sync_id": $body.indices.twitter.shards.0.0.commit.user_data.sync_id/]
<1> the `sync id` marker
NOTE: The `sync_id` marker is removed as soon as the shard is flushed again, and
{es} may trigger an automatic flush of a shard at any time if there are
unflushed operations in the shard's translog. In practice this means that one
should consider any indexing operation on an index as having removed its
`sync_id` markers.
[float]
==== Synced Flush API
The Synced Flush API allows an administrator to initiate a synced flush
manually. This can be particularly useful for a planned cluster restart where
you can stop indexing but don't want to wait for 5 minutes until all indices
are marked as inactive and automatically sync-flushed.
You can request a synced flush even if there is ongoing indexing activity, and
{es} will perform the synced flush on a "best-effort" basis: shards that do not
have any ongoing indexing activity will be successfully sync-flushed, and other
shards will fail to sync-flush. The successfully sync-flushed shards will have
faster recovery times as long as the `sync_id` marker is not removed by a
subsequent flush.
[source,console]
--------------------------------------------------
POST twitter/_flush/synced
--------------------------------------------------
// TEST[setup:twitter]
The response contains details about how many shards were successfully
sync-flushed and information about any failure.
Here is what it looks like when all shards of a two shards and one replica
index successfully sync-flushed:
[source,console-result]
--------------------------------------------------
{
"_shards": {
"total": 2,
"successful": 2,
"failed": 0
},
"twitter": {
"total": 2,
"successful": 2,
"failed": 0
}
}
--------------------------------------------------
// TESTRESPONSE[s/"successful": 2/"successful": 1/]
Here is what it looks like when one shard group failed due to pending
operations:
[source,js]
--------------------------------------------------
{
"_shards": {
"total": 4,
"successful": 2,
"failed": 2
},
"twitter": {
"total": 4,
"successful": 2,
"failed": 2,
"failures": [
{
"shard": 1,
"reason": "[2] ongoing operations on primary"
}
]
}
}
--------------------------------------------------
// NOTCONSOLE
NOTE: The above error is shown when the synced flush fails due to concurrent
indexing operations. The HTTP status code in that case will be `409 Conflict`.
Sometimes the failures are specific to a shard copy. The copies that failed
will not be eligible for fast recovery but those that succeeded still will be.
This case is reported as follows:
[source,js]
--------------------------------------------------
{
"_shards": {
"total": 4,
"successful": 1,
"failed": 1
},
"twitter": {
"total": 4,
"successful": 3,
"failed": 1,
"failures": [
{
"shard": 1,
"reason": "unexpected error",
"routing": {
"state": "STARTED",
"primary": false,
"node": "SZNr2J_ORxKTLUCydGX4zA",
"relocating_node": null,
"shard": 1,
"index": "twitter"
}
}
]
}
}
--------------------------------------------------
// NOTCONSOLE
NOTE: When a shard copy fails to sync-flush, the HTTP status code returned will
be `409 Conflict`.
The synced flush API can be applied to more than one index with a single call,
or even on `_all` the indices.
[source,console]
--------------------------------------------------
POST kimchy,elasticsearch/_flush/synced
POST _flush/synced
--------------------------------------------------
See <<indices-synced-flush-api>>.

281
docs/reference/indices/synced-flush.asciidoc Normal file
View File

@ -0,0 +1,281 @@
[[indices-synced-flush-api]]
=== Synced flush API
++++
<titleabbrev>Synced flush</titleabbrev>
++++
Performs a synced flush on one or more indices.
[source,console]
--------------------------------------------------
POST /twitter/_flush/synced
--------------------------------------------------
// TEST[setup:twitter]
[[synced-flush-api-request]]
==== {api-request-title}
`POST /<index>/flush/synced`
`GET /<index>/flush/synced`
`POST /flush/synced`
`GET /flush/synced`
[[synced-flush-api-desc]]
==== {api-description-title}
[[synced-flush-using-api]]
===== Use the synced flush API
Use the synced flush API to manually initiate a synced flush.
This can be useful for a planned cluster restart where
you can stop indexing but don't want to wait for 5 minutes until all indices
are marked as inactive and automatically sync-flushed.
You can request a synced flush even if there is ongoing indexing activity, and
{es} will perform the synced flush on a "best-effort" basis: shards that do not
have any ongoing indexing activity will be successfully sync-flushed, and other
shards will fail to sync-flush. The successfully sync-flushed shards will have
faster recovery times as long as the `sync_id` marker is not removed by a
subsequent flush.
[[synced-flush-overview]]
===== Synced flush overview
{es} keeps track of which shards have received indexing activity recently, and
considers shards that have not received any indexing operations for 5 minutes to
be inactive.
When a shard becomes inactive {es} performs a special kind of flush
known as a *synced flush*. A synced flush performs a normal
<<indices-flush,flush>> on each replica of the shard, and then adds a marker known
as the `sync_id` to each replica to indicate that these copies have identical
Lucene indices. Comparing the `sync_id` markers of the two copies is a very
efficient way to check whether they have identical contents.
When allocating shard replicas, {es} must ensure that each replica contains the
same data as the primary. If the shard copies have been synced-flushed and the
replica shares a `sync_id` with the primary then {es} knows that the two copies
have identical contents. This means there is no need to copy any segment files
from the primary to the replica, which saves a good deal of time during
recoveries and restarts.
This is particularly useful for clusters having lots of indices which are very
rarely updated, such as with time-based indices. Without the synced flush
marker, recovery of this kind of cluster would be much slower.
[[synced-flush-sync-id-markers]]
===== Check for `sync_id` markers
To check whether a shard has a `sync_id` marker or not, look for the `commit`
section of the shard stats returned by the <<indices-stats,indices stats>> API:
[source,console]
--------------------------------------------------
GET /twitter/_stats?filter_path=**.commit&level=shards <1>
--------------------------------------------------
// TEST[s/^/PUT twitter\nPOST twitter\/_flush\/synced\n/]
<1> `filter_path` is used to reduce the verbosity of the response, but is entirely optional
The API returns the following response:
[source,console-result]
--------------------------------------------------
{
"indices": {
"twitter": {
"shards": {
"0": [
{
"commit" : {
"id" : "3M3zkw2GHMo2Y4h4/KFKCg==",
"generation" : 3,
"user_data" : {
"translog_uuid" : "hnOG3xFcTDeoI_kvvvOdNA",
"history_uuid" : "XP7KDJGiS1a2fHYiFL5TXQ",
"local_checkpoint" : "-1",
"translog_generation" : "2",
"max_seq_no" : "-1",
"sync_id" : "AVvFY-071siAOuFGEO9P", <1>
"max_unsafe_auto_id_timestamp" : "-1",
"min_retained_seq_no" : "0"
},
"num_docs" : 0
}
}
]
}
}
}
}
--------------------------------------------------
// TESTRESPONSE[s/"id" : "3M3zkw2GHMo2Y4h4\/KFKCg=="/"id": $body.indices.twitter.shards.0.0.commit.id/]
// TESTRESPONSE[s/"translog_uuid" : "hnOG3xFcTDeoI_kvvvOdNA"/"translog_uuid": $body.indices.twitter.shards.0.0.commit.user_data.translog_uuid/]
// TESTRESPONSE[s/"history_uuid" : "XP7KDJGiS1a2fHYiFL5TXQ"/"history_uuid": $body.indices.twitter.shards.0.0.commit.user_data.history_uuid/]
// TESTRESPONSE[s/"sync_id" : "AVvFY-071siAOuFGEO9P"/"sync_id": $body.indices.twitter.shards.0.0.commit.user_data.sync_id/]
<1> the `sync id` marker
NOTE: The `sync_id` marker is removed as soon as the shard is flushed again, and
{es} may trigger an automatic flush of a shard at any time if there are
unflushed operations in the shard's translog. In practice this means that one
should consider any indexing operation on an index as having removed its
`sync_id` markers.
[[synced-flush-api-path-params]]
==== {api-path-parms-title}
include::{docdir}/rest-api/common-parms.asciidoc[tag=index]
+
To sync-flush all indices,
omit this parameter
or use a value of `_all` or `*`.
[[synced-flush-api-query-params]]
==== {api-query-parms-title}
include::{docdir}/rest-api/common-parms.asciidoc[tag=allow-no-indices]
include::{docdir}/rest-api/common-parms.asciidoc[tag=expand-wildcards]
+
Defaults to `open`.
include::{docdir}/rest-api/common-parms.asciidoc[tag=index-ignore-unavailable]
[[synced-flush-api-response-codes]]
==== {api-response-codes-title}
`200`::
All shards successfully sync-flushed.
`409`::
A replica shard failed to sync-flush.
[[synced-flush-api-example]]
==== {api-examples-title}
[[synced-flush-api-specific-ex]]
===== Sync-flush a specific index
[source,console]
----
POST /kimchy/_flush
----
// TEST[s/^/PUT kimchy\n/]
[[synced-flush-api-multi-ex]]
===== Synch-flush several indices
[source,console]
--------------------------------------------------
POST /kimchy,elasticsearch/_flush/synced
--------------------------------------------------
// TEST[s/^/PUT elasticsearch\n/]
// TEST[continued]
[[synced-flush-api-all-ex]]
===== Sync-flush all indices
[source,console]
--------------------------------------------------
POST /_flush/synced
--------------------------------------------------
// TEST[setup:twitter]
The response contains details about how many shards were successfully
sync-flushed and information about any failure.
The following response indicates two shards
and one replica shard
successfully sync-flushed:
[source,console-result]
--------------------------------------------------
{
"_shards": {
"total": 2,
"successful": 2,
"failed": 0
},
"twitter": {
"total": 2,
"successful": 2,
"failed": 0
}
}
--------------------------------------------------
// TESTRESPONSE[s/"successful": 2/"successful": 1/]
The following response indicates one shard group failed
due to pending operations:
[source,js]
--------------------------------------------------
{
"_shards": {
"total": 4,
"successful": 2,
"failed": 2
},
"twitter": {
"total": 4,
"successful": 2,
"failed": 2,
"failures": [
{
"shard": 1,
"reason": "[2] ongoing operations on primary"
}
]
}
}
--------------------------------------------------
// NOTCONSOLE
Sometimes the failures are specific to a shard replica. The copies that failed
will not be eligible for fast recovery but those that succeeded still will be.
This case is reported as follows:
[source,js]
--------------------------------------------------
{
"_shards": {
"total": 4,
"successful": 1,
"failed": 1
},
"twitter": {
"total": 4,
"successful": 3,
"failed": 1,
"failures": [
{
"shard": 1,
"reason": "unexpected error",
"routing": {
"state": "STARTED",
"primary": false,
"node": "SZNr2J_ORxKTLUCydGX4zA",
"relocating_node": null,
"shard": 1,
"index": "twitter"
}
}
]
}
}
--------------------------------------------------
// NOTCONSOLE

2
rest-api-spec/src/main/resources/rest-api-spec/api/indices.flush_synced.json
View File

@ -1,7 +1,7 @@
{
"indices.flush_synced":{
"documentation":{
"url":"https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-flush.html#synced-flush-api",
"url":"https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-synced-flush-api.html",
"description":"Performs a synced flush operation on one or more indices."
},
"stability":"stable",