Setting Thread Allocations

reference

The number of threads allocated per node is configurable.

HTTP method and URI

POST /pools/default/settings/memcached/global

Description

Couchbase Server allows the number of threads allocated per node for reading, writing, and for NonIO, and AuxIO thread-pools to be configured by the administrator.

A high thread-allocation may improve performance on systems whose hardware-resources are commensurately supportive (for example, where the number of CPU cores is high). In particular, a high number of writer threads on such systems may significantly optimize the performance of durable writes: see Durability, for information.

Note, however, that a high thread-allocation might impair some aspects of performance on less appropriately resourced nodes. Consequently, changes to the default thread-allocation should not be made to production systems without prior testing.

Curl Syntax

curl -X POST -d hostname=<ip-address-or-hostname>:8091
  -d num_reader_threads=<int>
  -d num_writer_threads=<int>
  -d num_nonio_threads=<int>
  -d num_auxio_threads=<int>
  -d password=<password>
  -u <administrator>:<password>
  http://<host>:<port>/pools/default/settings/memcached/global

Each key is specified optionally.

The keys num_reader_threads and num_writer_threads specify the number of threads that are to be used for reading and writing, respectively.

The keys num_nonio_threads and num_auxio_threads specify the number of threads that are to be used for NonIO and AuxIO thread pools, respectively. Note that:

The NonIO thread pool is used to run in memory tasks — for example, the durability timeout task.
The AuxIO thread pool is used to run auxiliary I/O tasks — for example, the access log task.

In all cases, the value of int should be an integer between 1 and 64, inclusive. If in any case the value default is specified (for example, -d num_reader_threads=default), Couchbase Server itself calculates and applies an appropriate number of threads.

Responses

Success returns an object whose values confirm the settings that have been made.

Examples

To set the numbers of reader, writer, NonIO, and AuxIO threads for Couchbase Server, use the POST /pools/default/settings/memcached/global http method and endpoint as follows:

curl -v -X POST -u Administrator:password \
http://10.144.220.101:8091/pools/default/settings/memcached/global \
-d num_reader_threads=12 \
-d num_writer_threads=8 \
-d num_nonio_threads=6 \
-d num_auxio_threads=6

This sets the number of reader threads to 12, the number of writer threads to 8, and the numbers of NonIO and AuxIO threads each to 6. If successful, the call returns an object whose values confirm the settings that have been made:

{"num_reader_threads":12,"num_writer_threads":8,"num_auxio_threads":6,"num_nonio_threads":6}