- Elasticsearch Guide: other versions:
- Getting Started
- Setup
- Breaking changes
- Breaking changes in 2.3
- Breaking changes in 2.2
- Breaking changes in 2.1
- Breaking changes in 2.0
- Removed features
- Network changes
- Multiple
path.data
striping - Mapping changes
- CRUD and routing changes
- Query DSL changes
- Search changes
- Aggregation changes
- Parent/Child changes
- Scripting changes
- Index API changes
- Snapshot and Restore changes
- Plugin and packaging changes
- Setting changes
- Stats, info, and
cat
changes - Java API changes
- API Conventions
- Document APIs
- Search APIs
- Aggregations
- Metrics Aggregations
- Avg Aggregation
- Cardinality Aggregation
- Extended Stats Aggregation
- Geo Bounds Aggregation
- Geo Centroid Aggregation
- Max Aggregation
- Min Aggregation
- Percentiles Aggregation
- Percentile Ranks Aggregation
- Scripted Metric Aggregation
- Stats Aggregation
- Sum Aggregation
- Top hits Aggregation
- Value Count Aggregation
- Bucket Aggregations
- Children Aggregation
- Date Histogram Aggregation
- Date Range Aggregation
- Filter Aggregation
- Filters Aggregation
- Geo Distance Aggregation
- GeoHash grid Aggregation
- Global Aggregation
- Histogram Aggregation
- IPv4 Range Aggregation
- Missing Aggregation
- Nested Aggregation
- Range Aggregation
- Reverse nested Aggregation
- Sampler Aggregation
- Significant Terms Aggregation
- Terms Aggregation
- Pipeline Aggregations
- Avg Bucket Aggregation
- Derivative Aggregation
- Max Bucket Aggregation
- Min Bucket Aggregation
- Sum Bucket Aggregation
- Stats Bucket Aggregation
- Extended Stats Bucket Aggregation
- Percentiles Bucket Aggregation
- Moving Average Aggregation
- Cumulative Sum Aggregation
- Bucket Script Aggregation
- Bucket Selector Aggregation
- Serial Differencing Aggregation
- Caching heavy aggregations
- Returning only aggregation results
- Aggregation Metadata
- Metrics Aggregations
- Indices APIs
- Create Index
- Delete Index
- Get Index
- Indices Exists
- Open / Close Index API
- Put Mapping
- Get Mapping
- Get Field Mapping
- Types Exists
- Index Aliases
- Update Indices Settings
- Get Settings
- Analyze
- Index Templates
- Warmers
- Shadow replica indices
- Indices Stats
- Indices Segments
- Indices Recovery
- Indices Shard Stores
- Clear Cache
- Flush
- Refresh
- Force Merge
- Optimize
- Upgrade
- cat APIs
- Cluster APIs
- Query DSL
- Mapping
- Field datatypes
- Meta-Fields
- Mapping parameters
analyzer
boost
coerce
copy_to
doc_values
dynamic
enabled
fielddata
format
geohash
geohash_precision
geohash_prefix
ignore_above
ignore_malformed
include_in_all
index
index_options
lat_lon
fields
norms
null_value
position_increment_gap
precision_step
properties
search_analyzer
similarity
store
term_vector
- Dynamic Mapping
- Transform
- Analysis
- Analyzers
- Tokenizers
- Token Filters
- Standard Token Filter
- ASCII Folding Token Filter
- Length Token Filter
- Lowercase Token Filter
- Uppercase Token Filter
- NGram Token Filter
- Edge NGram Token Filter
- Porter Stem Token Filter
- Shingle Token Filter
- Stop Token Filter
- Word Delimiter Token Filter
- Stemmer Token Filter
- Stemmer Override Token Filter
- Keyword Marker Token Filter
- Keyword Repeat Token Filter
- KStem Token Filter
- Snowball Token Filter
- Phonetic Token Filter
- Synonym Token Filter
- Compound Word Token Filter
- Reverse Token Filter
- Elision Token Filter
- Truncate Token Filter
- Unique Token Filter
- Pattern Capture Token Filter
- Pattern Replace Token Filter
- Trim Token Filter
- Limit Token Count Token Filter
- Hunspell Token Filter
- Common Grams Token Filter
- Normalization Token Filter
- CJK Width Token Filter
- CJK Bigram Token Filter
- Delimited Payload Token Filter
- Keep Words Token Filter
- Keep Types Token Filter
- Classic Token Filter
- Apostrophe Token Filter
- Decimal Digit Token Filter
- Character Filters
- Modules
- Index Modules
- Testing
- Glossary of terms
- Release Notes
- 2.3.5 Release Notes
- 2.3.4 Release Notes
- 2.3.3 Release Notes
- 2.3.2 Release Notes
- 2.3.1 Release Notes
- 2.3.0 Release Notes
- 2.2.2 Release Notes
- 2.2.1 Release Notes
- 2.2.0 Release Notes
- 2.1.2 Release Notes
- 2.1.1 Release Notes
- 2.1.0 Release Notes
- 2.0.2 Release Notes
- 2.0.1 Release Notes
- 2.0.0 Release Notes
- 2.0.0-rc1 Release Notes
- 2.0.0-beta2 Release Notes
- 2.0.0-beta1 Release Notes
WARNING: Version 2.3 of Elasticsearch has passed its EOL date.
This documentation is no longer being maintained and may be removed. If you are running this version, we strongly advise you to upgrade. For the latest information, see the current release documentation.
Synced Flush
editSynced Flush
editElasticsearch tracks the indexing activity of each shard. Shards that have not
received any indexing operations for 5 minutes are automatically marked as inactive. This presents
an opportunity for Elasticsearch to reduce shard resources and also perform
a special kind of flush, called synced flush
. A synced flush performs a normal flush, then adds
a generated unique marker (sync_id) to all shards.
Since the sync id marker was added when there were no ongoing indexing operations, it can be used as a quick way to check if the two shards' lucene indices are identical. This quick sync id comparison (if present) is used during recovery or restarts to skip the first and most costly phase of the process. In that case, no segment files need to be copied and the transaction log replay phase of the recovery can start immediately. Note that since the sync id marker was applied together with a flush, it is very likely that the transaction log will be empty, speeding up recoveries even more.
This is particularly useful for use cases having lots of indices which are never or very rarely updated, such as time based data. This use case typically generates lots of indices whose recovery without the synced flush marker would take a long time.
To check whether a shard has a marker or not, look for the commit
section of shard stats returned by
the indices stats API:
GET /twitter/_stats/commit?level=shards
which returns something similar to:
{ ... "indices": { "twitter": { "primaries": {}, "total": {}, "shards": { "0": [ { "routing": { ... }, "commit": { "id": "te7zF7C4UsirqvL6jp/vUg==", "generation": 2, "user_data": { "sync_id": "AU2VU0meX-VX2aNbEUsD" , ... }, "num_docs": 0 } } ... ], ... } } } }
Synced Flush API
editThe Synced Flush API allows an administrator to initiate a synced flush manually. This can be particularly useful for a planned (rolling) cluster restart where you can stop indexing and don’t want to wait the default 5 minutes for idle indices to be sync-flushed automatically.
While handy, there are a couple of caveats for this API:
- Synced flush is a best effort operation. Any ongoing indexing operations will cause the synced flush to fail on that shard. This means that some shards may be synced flushed while others aren’t. See below for more.
-
The
sync_id
marker is removed as soon as the shard is flushed again. That is because a flush replaces the low level lucene commit point where the marker is stored. Uncommitted operations in the transaction log do not remove the marker. In practice, one should consider any indexing operation on an index as removing the marker as a flush can be triggered by Elasticsearch at any time.
It is harmless to request a synced flush while there is ongoing indexing. Shards that are idle will succeed and shards that are not will fail. Any shards that succeeded will have faster recovery times.
POST /twitter/_flush/synced
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:
{ "_shards": { "total": 4, "successful": 4, "failed": 0 }, "twitter": { "total": 4, "successful": 4, "failed": 0 } }
Here is what it looks like when one shard group failed due to pending operations:
{ "_shards": { "total": 4, "successful": 2, "failed": 2 }, "twitter": { "total": 4, "successful": 2, "failed": 2, "failures": [ { "shard": 1, "reason": "[2] ongoing operations on primary" } ] } }
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:
{ "_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" } } ] } }
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.
POST /kimchy,elasticsearch/_flush/synced POST /_flush/synced
On this page