Increasing the size of the queue in Elasticsearch? - exception

Question

Ive been looking at my elasticsearch logs, and I came across the error
rejected execution (queue capacity 1000) on org.elasticsearch.search.action.SearchServiceTransportAction$23#6d32fa18
After looking up the error, the general and consensus was to increase the size of the queue as talked about here - https://www.elastic.co/guide/en/elasticsearch/reference/current/modules-threadpool.html
The question I have is how to do I actually do this? Is there aconfiguration file somewhere that I am missing?

Answer 1

From Elasticsearch 5 onward you cannot use the API to update the threadpool search queue size. It is now a node-level settings. See this.
Thread pool settings are now node-level settings. As such, it is not possible to update thread pool settings via the cluster settings API.
To update the threadpool you have to add thread_pool.search.queue_size : <New size> in elasticsearch.yml file of each node and then restart elasticsearch.

Answer 2

To change the queue size one could add it in the config file for each of the nodes as follows:
threadpool.search.queue_size: <new queue size> .
However this would also require a cluster restart.
Up to Elasticsearch 2.x, you can update via the cluster-setting api and this would not require a cluster restart, however this option is gone with Elasticsearch 5.x and newer.
curl -XPUT _cluster/settings -d '{
"persistent" : {
"threadpool.search.queue_size" : <new_size>
}
}'
You can query the queue size as follows:
curl <server>/_cat/thread_pool?v&h=search.queueSize

Answer 3

As of Elasticsearch 6 the type of the search thread pool has changed to fixed_auto_queue_size, which means setting threadpool.search.queue_size in elasticsearch.yml is not enough, you have to control the min_queue_size and max_queue_size parameters as well, like this:
thread_pool.search.queue_size: <new_size>
thread_pool.search.min_queue_size: <new_size>
thread_pool.search.max_queue_size: <new_size>
I recommend using _cluster/settings?include_defaults=true to view the current thread pool settings in your nodes before making any changes. For more information about the fixed_auto_queue_size thread pool read the docs.