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baron@percona.com
2012-01-21 09:15:45 -05:00
parent 51b93a6235
commit 63ea85e755
1 changed files with 87 additions and 43 deletions
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bin/pt-stalk
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@@ -926,7 +926,7 @@ main() {
RAN_WITH="--function=$OPT_FUNCTION --variable=$OPT_VARIABLE --threshold=$OPT_THRESHOLD --match=$OPT_MATCH --cycles=$OPT_CYCLES --interval=$OPT_INTERVAL --iterations=$OPT_ITERATIONS --run-time=$OPT_RUN_TIME --sleep=$OPT_SLEEP --dest=$OPT_DEST --prefix=$OPT_PREFIX --notify-by-email=$OPT_NOTIFY_BY_EMAIL --log=$OPT_LOG --pid=$OPT_PID"
log "Starting $0 $RAN_WITH"
# Make the collection dir exists.
# Make sure the collection dir exists.
if [ ! -d "$OPT_DEST" ]; then
mkdir -p "$OPT_DEST" || die "Cannot make --dest $OPT_DEST"
fi
@@ -1033,16 +1033,17 @@ fi
=head1 NAME
pt-stalk - Wait for a condition to occur then begin collecting data.
pt-stalk - Gather forensic data about MySQL when a problem occurs.
=head1 SYNOPSIS
Usage: pt-stalk [OPTIONS] [-- MYSQL OPTIONS]
pt-stalk watches for a condition to become true, and when it does, executes
a script. By default it executes L<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.
pt-stalk watches for a trigger condition to become true, and then collects data
to help in diagnosing problems. It is designed to run as a daemon so that you
can diagnose intermittent problems that you cannot observe directly. You can
also use it to execute a custom command, or to gather the data on demand without
waiting for the trigger to happen.
=head1 RISKS
@@ -1051,7 +1052,9 @@ 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.
pt-stalk is a read-only tool. It should be very low-risk. Some of the options
can cause intrusive data collection to be performed, however, so if you enable
any non-default options, you should read their documentation carefully.
At the time of this release, we know of no bugs that could cause serious harm
to users.
@@ -1065,37 +1068,42 @@ See also L<"BUGS"> for more information on filing bugs and getting help.
=head1 DESCRIPTION
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:
Sometimes a problem happens infrequently and for a short time, giving you no
chance to see the system when it happens. How do you solve intermittent MySQL
problems when you can't observe them? That's why pt-stalk exists. In addition to
using it when there's a known problem on your servers, it is a good idea to run
pt-stalk all the time, even when you think nothing is wrong. You will
appreciate the data it gathers when a problem occurs, because problems such as
MySQL lockups or spikes of activity typically leave no evidence to use in root
cause analysis.
=over
This tool does two things: it watches a server (typically MySQL) for a trigger
to occur, and it gathers diagnostic data. To use it effectively, you need to
define a good trigger condition. A good trigger is sensitive enough to fire
reliably when a problem occurs, so that you don't miss a chance to solve
problems. On the other hand, a good trigger isn't prone to false positives, so
you don't gather information when the server is functioning normally.
=item 1.
The most reliable triggers for MySQL tend to be the number of connections to the
server, and the number of queries running concurrently. These are available in
the SHOW GLOBAL STATUS command as Threads_connected and Threads_running.
Sometimes Threads_connected is not a reliable indicator of trouble, but
Threads_running usually is. Your job, as the tool's user, is to define an
appropriate trigger condition for the tool. Choose carefully, because the
quality of your results will depend on the trigger you choose.
Loop infinitely, sleeping between iterations.
The pt-stalk tool, by default, simply watches MySQL repeatedly until the trigger
becomes true. It then gathers diagnostics for a while, and sleeps afterwards for
some time to prevent repeatedly gathering data if the condition remains true.
=item 2.
The diagnostic data is written to files whose names begin with a timestamp, so
you can distinguish samples from each other in case the tool collects data
multiple times. The pt-sift tool is designed to help you browse and analyze the
resulting samples of data.
In each iteration, run some command and get the output.
=item 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.
=back
By default, the tool is configured to execute mysqladmin extended-status and
extract the value of the Threads_running variable; if this is greater than
25, 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.
Although this sounds simple enough, in practice there are a number of
subtleties, such as detecting when the disk is beginning to fill up so that the
tool doesn't cause the server to run out of disk space.
=head1 CONFIGURING
@@ -1109,51 +1117,87 @@ TODO
default: yes; negatable: yes
Collect system information.
Collect system information. You can negate this option to make the tool watch
the system but not actually gather any diagnostic data.
=item --collect-gdb
Collect GDB stacktraces.
Collect GDB stacktraces. This is achieved by attaching to MySQL and printing
stack traces from all threads. This will freeze the server for some period of
time, ranging from a second or so to much longer on very busy systems with a lot
of memory and many threads in the server. For this reason, it is disabled by
default. However, if you are trying to diagnose a server stall or lockup,
freezing the server causes no additional harm, and the stack traces can be vital
for diagnosis.
In addition to freezing the server, there is also some risk of the server
crashing or performing badly after GDB detaches from it.
=item --collect-oprofile
Collect oprofile data.
Collect oprofile data. This is achieved by starting an oprofile session,
letting it run for the collection time, and then stopping and saving the
resulting profile data in the system's default location. Please read your
system's oprofile documentation to learn more about this.
=item --collect-strace
Collect strace data.
Collect strace data. This is achieved by attaching strace to the server, which
will make it run very slowly until strace detaches. The same cautions apply as
those listed in --collect-gdb. You should not enable this option together with
--collect-gdb, because GDB and strace can't attach to the server process
simultaneously.
=item --collect-tcpdump
Collect tcpdump data.
Collect tcpdump data. This option causes tcpdump to capture all traffic on all
interfaces for the port on which MySQL is listening. You can later use
pt-query-digest to decode the MySQL protocol and extract a log of query traffic
from it.
=item --cycles
type: int; default: 5
Number of times condition must be met before triggering collection.
The number of times the trigger condition must be true before collecting data.
This helps prevent false positives and make the trigger condition less
susceptible to firing when the condition recovers quickly.
=item --daemonize
Daemonize the tool.
Daemonize the tool. This causes the tool to fork into the background and log
its output as specified in --log.
=item --dest
type: string; default: ${HOME}/collected
Where to store collected data.
Where to store the diagnostic data. Each time the tool collects data, it writes
to a new set of files, which are named with the current system timestamp.
=item --disk-byte-limit
type: int; default: 100
Exit if the disk has less than this many MB free.
Don't collect data unless the destination disk has this much free space. This
prevents the tool from filling up the disk with diagnostic data.
If the destination directory contains a previously captured sample of data, the
tool will measure its size and use that as an estimate of how much data is
likely to be gathered this time, too. It will then be even more pessimistic,
and will refuse to collect data unless the disk has enough free space to hold
the sample and still have the desired amount of free space. For example, if
you'd like 100MB of free space and the previous diagnostic sample consumed
100MB, the tool won't collect any data unless the disk has 200MB free.
=item --disk-pct-limit
type: int; default: 5
Exit if the disk is less than this %full.
Don't collect data unless the disk has at least this percent free space. This
option works similarly to --disk-byte-limit, but specifies a percentage margin
of safety instead of a byte margin of safety. The tool honors both options, and
will not collect any data unless both margins are satisfied.
=item --function