The thread pool feature comprises these components:
A plugin library object file contains a plugin for the thread pool code and plugins for several
For a detailed description of how the thread pool works, see Section 126.96.36.199, “Thread Pool Operation”.
INFORMATION_SCHEMAtables are named
TP_THREAD_GROUP_STATS. These tables provide information about thread pool operation. For more information, see Section 21.30, “Thread Pool INFORMATION_SCHEMA Tables”.
Several system variables are related to the thread pool. The
thread_handlingsystem variable has a value of
loaded-dynamicallywhen the server successfully loads the thread pool plugin.
The other related variables are implemented by the thread pool plugin; they are not available unless it is enabled:
thread_pool_algorithm: The concurrency algorithm to use for scheduling.
thread_pool_high_priority_connection: How to schedule statement execution for a session.
thread_pool_prio_kickup_timer: How long before the thread pool moves a statement awaiting execution from the low-priority queue to the high-priority queue.
thread_pool_max_unused_threads: How many sleeping threads to permit.
thread_pool_size: The number of thread groups in the thread pool. This is the most important parameter controlling thread pool performance.
thread_pool_stall_limit: The time before an executing statement is considered to be stalled.
If any variable implemented by the plugin is set to an illegal value at startup, plugin initialization fails and the plugin does not load.
For information about setting thread pool parameters, see Section 188.8.131.52, “Thread Pool Tuning”.
The Performance Schema exposes information about the thread pool and may be used to investigate operational performance. For more information, see Chapter 22, MySQL Performance Schema.
To be usable by the server, the thread pool library object
file must be located in the MySQL plugin directory (the
directory named by the
plugin_dir system variable).
To enable thread pool capability, load the plugins to be used
by starting the server with the
--plugin-load option. For
example, if you name just the plugin object file, the server
loads all plugins that it contains (that is, the thread pool
plugin and all the
tables). To do this, put these lines in your
That is equivalent to loading all thread pool plugins by naming them individually:
[mysqld] plugin-load=thread_pool.so plugin-load=thread_pool=thread_pool.so;tp_thread_state=thread_pool.so;tp_thread_group_state=thread_pool.so;tp_thread_group_stats=thread_pool.so
If object files have a suffix different from
.so on your system, substitute the
correct suffix (for example,
If necessary, set the value of the
plugin_dir system variable to
tell the server the location of the plugin directory.
If desired, you can load individual plugins from the library
file. To load the thread pool plugin but not the
INFORMATION_SCHEMA tables, use an option
To load the thread pool plugin and only the
INFORMATION_SCHEMA table, use an option
However, if you do not load all the
INFORMATION_SCHEMA tables, some or all
MySQL Enterprise Monitor thread pool graphs will be empty.
To verify plugin installation, examine the
or use the
statement. See Section 184.108.40.206, “Obtaining Server Plugin Information”.
If the server loads the thread plugin successfully, it sets
thread_handling system variable to
dynamically-loaded. If the plugin fails to
load, the server writes a message to the error log.