pt-stalk - Wait for a condition to occur then begin collecting data.


Usage: pt-stalk

pt-stalk watches for a condition to become true, and when it does, executes a script. By default it executes pt-collect, but that can be customized. This tool is useful for gathering diagnostic data when an infrequent event occurs, so an expert person can review the data later.


The following section is included to inform users about the potential risks, whether known or unknown, of using this tool. The two main categories of risks are those created by the nature of the tool (e.g. read-only tools vs. read-write tools) and those created by bugs.

pt-stalk is a read-only tool. It should be very low-risk.

At the time of this release, we know of no bugs that could cause serious harm to users.

The authoritative source for updated information is always the online issue tracking system. Issues that affect this tool will be marked as such. You can see a list of such issues at the following URL:

See also “BUGS” for more information on filing bugs and getting help.


Although pt-stalk comes pre-configured to do a specific thing, in general this tool is just a skeleton script for the following flow of actions:

  1. Loop infinitely, sleeping between iterations.
  2. In each iteration, run some command and get the output.
  3. If the command fails or the output is larger than the threshold, execute the collection script; but do not execute if the destination disk is too full.

By default, the tool is configured to execute mysqladmin extended-status and extract the value of the Threads_connected variable; if this is greater than 100, it runs the collection script. This is really just placeholder code, and almost certainly needs to be customized!

If the tool does execute the collection script, it will wait for a while before checking and executing again. This is to prevent a continuous condition from causing a huge number of executions to fire off.

The name ‘stalk’ is because ‘watch’ is already taken, and ‘stalk’ is fun.


If the file pt-stalk.conf exists in the current working directory, then “ENVIRONMENT” variables are imported from it. For example, the config file has the format:




This tool does not have any command-line options, but see “ENVIRONMENT” and “CONFIGURING”.


The following environment variables configure how, what, and when the tool runs. They are all optional and can be specified either on the command line or in the pt-stalk.conf config file (see “CONFIGURING”).

THRESHOLD (default 100)

This is the max number of <whatever> we want to tolerate.

VARIABLE (default Threads_connected}

This is the thing to check for.

CYCLES (default 1)

How many times must the condition be met before the script will fire?

GDB (default no)

Collect GDB stacktraces?

OPROFILE (default yes)

Collect oprofile data?

STRACE (default no)

Collect strace data?

TCPDUMP (default yes)

Collect tcpdump data?


Send mail to this list of addresses when the script triggers.


Any options to pass to mysql/mysqladmin, such as -u, -p, etc

INTERVAL (default 30)

This is the interval between checks.

MAYBE_EMPTY (default no)

If the command you’re running to detect the condition is allowed to return nothing (e.g. a grep line that might not even exist if there’s no problem), then set this to “yes”.

COLLECT (default ${HOME}/bin/pt-collect)

This is the location of the ‘collect’ script.

DEST (default ${HOME}/collected/)

This is where to store the collected data.

DURATION (default 30)

How long to collect statistics data for? Make sure that this isn’t longer than SLEEP.

SLEEP (default DURATION * 10)

How long to sleep after collecting?

PCT_THRESHOLD (default 95)

Bail out if the disk is more than this %full.

MB_THRESHOLD (default 100)

Bail out if the disk has less than this many MB free.

PURGE (default 30)

Remove samples after this many days.


This tool requires Bash v3 or newer.


For a list of known bugs, see

Please report bugs at Include the following information in your bug report:

* Complete command-line used to run the tool

* Tool “–version”

* MySQL version of all servers involved

* Output from the tool including STDERR

* Input files (log/dump/config files, etc.)

If possible, include debugging output by running the tool with PTDEBUG; see “ENVIRONMENT”.


Visit to download the latest release of Percona Toolkit. Or, get the latest release from the command line:




You can also get individual tools from the latest release:


Replace TOOL with the name of any tool.


Baron Schwartz, Justin Swanhart, and Fernando Ipar


This tool is part of Percona Toolkit, a collection of advanced command-line tools developed by Percona for MySQL support and consulting. Percona Toolkit was forked from two projects in June, 2011: Maatkit and Aspersa. Those projects were created by Baron Schwartz and developed primarily by him and Daniel Nichter, both of whom are employed by Percona. Visit for more software developed by Percona.


pt-stalk 1.0.2

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