WARNING: Version 2.2 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 (defaults to five minutes). 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. Sometimes, the number of processors
are wrongly detected, in such cases, the number of processors can be
explicitly set using the processors
setting.
In order to check the number of processors detected, use the nodes info
API with the os
flag.