- Elasticsearch Guide: other versions:
- Getting Started
- Setup
- Breaking changes
- Breaking changes in 2.4
- 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
- Dots in field names
- 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
- 2.4.6 Release Notes
- 2.4.5 Release Notes
- 2.4.4 Release Notes
- 2.4.3 Release Notes
- 2.4.2 Release Notes
- 2.4.1 Release Notes
- 2.4.0 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 2.4 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.
Thread Pool
editThread Pool
editA node holds several thread pools in order to improve how threads memory consumption are managed within a node. Many of these pools also have queues associated with them, which allow pending requests to be held instead of discarded.
There are several thread pools, but the important ones include:
-
generic
-
For generic operations (e.g., background node discovery).
Thread pool type is
cached
. -
index
-
For index/delete operations. Thread pool type is
fixed
with a size of# of available processors
, queue_size of200
. -
search
-
For count/search operations. Thread pool type is
fixed
with a size ofint((# of available_processors * 3) / 2) + 1
, queue_size of1000
. -
suggest
-
For suggest operations. Thread pool type is
fixed
with a size of# of available processors
, queue_size of1000
. -
get
-
For get operations. Thread pool type is
fixed
with a size of# of available processors
, queue_size of1000
. -
bulk
-
For bulk operations. Thread pool type is
fixed
with a size of# of available processors
, queue_size of50
. -
percolate
-
For percolate operations. Thread pool type is
fixed
with a size of# of available processors
, queue_size of1000
. -
snapshot
-
For snapshot/restore operations. Thread pool type is
scaling
with a keep-alive of5m
and a size ofmin(5, (# of available processors)/2)
. -
warmer
-
For segment warm-up operations. Thread pool type is
scaling
with a keep-alive of5m
and a size ofmin(5, (# of available processors)/2)
. -
refresh
-
For refresh operations. Thread pool type is
scaling
with a keep-alive of5m
and a size ofmin(10, (# of available processors)/2)
. -
listener
-
Mainly for java client executing of action when listener threaded is set to true.
Thread pool type is
scaling
with a default size ofmin(10, (# of available processors)/2)
.
Changing a specific thread pool can be done by setting its type-specific parameters; for example, changing the index
thread pool to have more threads:
threadpool: index: size: 30
you can update thread pool settings dynamically using Cluster Update Settings.
Thread pool types
editThe following are the types of thread pools and their respective parameters:
cached
editThe cached
thread pool is an unbounded thread pool that will spawn a
thread if there are pending requests. This thread pool is used to
prevent requests submitted to this pool from blocking or being
rejected. Unused threads in this thread pool will be terminated after
a keep alive expires. The cached
thread pool is reserved for
the generic
thread pool.
The keep_alive
parameter determines how long a thread should be kept
around in the thread pool without doing any work.
threadpool: generic: keep_alive: 2m
fixed
editThe fixed
thread pool holds a fixed size of threads to handle the
requests with a queue (optionally bounded) for pending requests that
have no threads to service them.
The size
parameter controls the number of threads, and defaults to the
number of cores times 5.
The queue_size
allows to control the size of the queue of pending
requests that have no threads to execute them. By default, it is set to
-1
which means its unbounded. When a request comes in and the queue is
full, it will abort the request.
threadpool: index: size: 30 queue_size: 1000
scaling
editThe scaling
thread pool holds a dynamic number of threads. This number is
proportional to the workload and varies between 1 and the value of the
size
parameter.
The keep_alive
parameter determines how long a thread should be kept
around in the thread pool without it doing any work.
threadpool: warmer: size: 8 keep_alive: 2m
Processors setting
editThe number of processors is automatically detected, and the thread pool
settings are automatically set based on it. In some cases it can be
useful to override the number of detected processors. This can be done
by explicitly setting the processors
setting.
processors: 2
There are a few use-cases for explicitly overriding the processors
setting:
-
If you are running multiple instances of Elasticsearch on the same
host but want Elasticsearch to size its thread pools as if it only has a
fraction of the CPU, you should override the
processors
setting to the desired fraction (e.g., if you’re running two instances of Elasticsearch on a 16-core machine, setprocessors
to 8). Note that this is an expert-level use-case and there’s a lot more involved than just setting theprocessors
setting as there are other considerations like changing the number of garbage collector threads, pinning processes to cores, etc. -
The number of processors is by default bounded to 32. This means that
on systems that have more than 32 processors, Elasticsearch will size
its thread pools as if there are only 32 processors present. This
limitation was added to avoid creating too many threads on systems that
have not properly adjusted the
ulimit
for max number of processes. In cases where you’ve adjusted theulimit
appropriately, you can override this bound by explicitly setting theprocessors
setting. -
Sometimes the number of processors is wrongly detected and in such
cases explicitly setting the
processors
setting will workaround such issues.
In order to check the number of processors detected, use the nodes info
API with the os
flag.