5.7.1.1. Connection Probes

The connection-start and connection-done probes enclose a connection from a client, regardless of whether the connection is through a socket or network connection.

connection-start(connectionid, user, host)connection-done(status, connectionid)

connection-start: Triggered after a connection and successful login/authentication have been completed by a client. The arguments contain the connection information:
- connectionid: An unsigned long containing the connection ID. This is the same as the process ID shown as the Id value in the output from SHOW PROCESSLIST.
- user: The username used when authenticating. The value will be blank for the anonymous user.
- host: The host of the client connection. For a connection made using UNIX sockets, the value will be blank.
connection-done: Triggered just as the connection to the client has been closed. The arguments are:
- status: The status of the connection when it was closed. A logout operation will have a value of 0; any other termination of the connection has a nonzero value.
- connectionid: The connection ID of the connection that was closed.

The following D script will quantify and summarize the average duration of individual connections, and provide a count, dumping the information every 60 seconds:

#!/usr/sbin/dtrace -smysql*:::connection-start{  self->start = timestamp;}mysql*:::connection-done/self->start/{  @ = quantize(((timestamp - self->start)/1000000));  self->start = 0;}tick-60s{  printa(@);}

When executed on a server with a large number of clients you might see output similar to this:

  1  57413                        :tick-60s           value  ------------- Distribution ------------- count              -1 |                                         0               0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 30011               1 |                                         59               2 |                                         5               4 |                                         20               8 |                                         29              16 |                                         18              32 |                                         27              64 |                                         30             128 |                                         11             256 |                                         10             512 |                                         1            1024 |                                         6            2048 |                                         8            4096 |                                         9            8192 |                                         8           16384 |                                         2           32768 |                                         1           65536 |                                         1          131072 |                                         0          262144 |                                         1524288 |                                         0