A node holds several thread pools in order to improve how threads are managed and memory consumption within a node. There are several thread pools, but the important ones include:
index: For index/delete/bulk operations (defaults tocachetype).search: For get/count/search operations (defaults tocachetype).
Changing a specific thread pool can be done by setting its type and specific type parameters, for example, changing the index thread pool to blocking type:
threadpool:
index:
type: blocking
min: 1
size: 30
wait_time: 30s
The following are the types of thread pools that can be used and their respective parameters:
cache
The cache thread pool is an unbounded thread pool that will spawn a thread if there are pending requests. Here is an example of how to set it:
threadpool:
index:
type: cached
fixed
The 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, the reject_policy parameter can control how it will behave. The default, abort, will simply fail the request. Setting it to caller will cause the request to execute on an IO thread allowing to throttle the execution on the networking layer.
threadpool:
index:
type: fixed
size: 30
queue: 1000
reject_policy: caller
blocking
The blocking pool allows to configure a min (defaults to 1) and size (defaults to the number of cores times 5) parameters for the number of threads.
It also has a backlog queue with a default queue_size of 1000. Once the queue is full, it will wait for the provided wait_time (defaults to 60s) on the calling IO thread, and fail if it has not been executed.
threadpool:
index:
type: blocking
min: 1
size: 30
wait_time: 30s
