29.12.16.1 The tp_connections Table

The tp_connections table contains one row per connection managed by the Thread Pool plugin. Each row provides information about the current state of a thread pool connection.

The tp_connections table contains the following rows:

• CONNECTION_ID

  The connection ID as reported by SELECT CONNECTION_ID().

• TP_GROUP_ID

  The index of the thread group in the global array. This column and TP_PROCESSING_THREAD_NUMBER serve as a foreign key into the tp_thread_state table.

• TP_PROCESSING_THREAD_NUMBER

  This may be NULL if no thread is currently attached to the connection.

• THREAD_ID

  The Performance Schema thread ID.

• STATE

  The connection state; this is one of Established, Armed, Queued, Waiting for Credit, Attached, Expired, or Killed.

• ACTIVE_FLAG

  When this is 0, the connection is not attached to any worker thread.

• KILLED_STATE

  Reports the current stage in the process of killing the connection.

• CLEANUP_STATE

  Reports the current stage in the cleanup process when closing the connection.

• TIME_OF_LAST_EVENT_COMPLETION

  Timestamp showing when the connection last processed a request.

• TIME_OF_EXPIRY

  Timestamp showing when an idle connection will expire if no new request arrives before then; this is NULL when the thread is currently processing a request.

• TIME_OF_ADD

  Timestamp showing when the connection was added to the thread pool's connection request queue.

• TIME_OF_POP

  Timestamp showing when the connection was dequeued (popped) from the queue by a connection handler thread.

• TIME_OF_ARM

  Timestamp showing when the connection file descriptor was last added to the set monitored by poll() or epoll().

• CONNECT_HANDLER_INDEX

  The index of the connection handler thread in the group which processed the connection request; a higher number means the connection load has triggered the creation of additional connection handler threads.

• TYPE

  The connection type; this is one of User, Admin_interface or Admin_privilege; Admin_privilege means that this connection had been using the normal interface, but was placed in the admin group due to the user having the TP_CONNECTION_ADMIN privilege.

• DIRECT_QUERY_EVENTS

  The number of queries executed directly by this connection.

• QUEUED_QUERY_EVENTS

  The number of queued queries executed by this connection.

• TIME_OF_EVENT_ARRIVAL

  A timestamp showing when poll_wait() returns with an event for the connection; this value is needed to calculate MANAGEMENT_TIME.

• MANAGEMENT_TIME

  The accumulated time between the return from waiting on file descriptors; this includes the time spent queued for queries which are not executed directly.