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.TH dbstat 8 "2017-02-15" "USER COMMANDS"
.SH NAME
dbstat \- Collect histograms of MySQL/PostgreSQL query latencies.
.SH SYNOPSIS
. B dbstat [-v] [-p PID [PID ...]] [-m THRESHOLD] [-u] [-i INTERVAL] {mysql,postgres}
.SH DESCRIPTION
This traces queries served by a MySQL or PostgreSQL server, and collects a
histogram of query latencies. The histogram is printed at the end of collection,
or at specified intervals.
This uses User Statically-Defined Tracing (USDT) probes, a feature added to
MySQL and PostgreSQL for DTrace support, but which may not be enabled on a
given installation. See requirements.
Since this uses BPF, only the root user can use this tool.
.SH REQUIREMENTS
CONFIG_BPF, bcc, and MySQL server with USDT probe support (when configuring
the build: \-DENABLE_DTRACE=1) or PostgreSQL server with USDT probe support
(when configuring the build: \-\-enable-dtrace).
.SH OPTIONS
\-h
Print usage message.
.TP
\-p PID
Trace this PID. If no PID is specified, the tool will attempt to automatically
detect the MySQL or PostgreSQL processes running on the system.
.TP
\-m THRESHOLD
Minimum query latency (duration) to trace, in milliseconds.
Default is all queries.
.TP
\-u
Display query latencies in microseconds (default: milliseconds).
.TP
\-i INTERVAL
Print summaries (histograms) at this interval, specified in seconds.
.TP
{mysql,postgres}
The database engine to trace.
.SH EXAMPLES
.TP
Display histogram of MySQL query latencies:
#
.B dbstat mysql
.TP
Display histogram of PostgreSQL query latencies slower than 10ms in pid 408:
#
.B dbstat postgres -p 408 -m 10
.TP
Display histogram of PostgreSQL query latencies at 3-second intervals:
#
.B dbstat postgres -i 3
.SH OVERHEAD
This adds low-overhead instrumentation to queries, and only emits output
data from kernel to user-level if they query exceeds the threshold. If the
server query rate is less than 1,000/sec, the overhead is expected to be
negligible. If the query rate is higher, test to gauge overhead.
.SH SOURCE
This is from bcc.
.IP
https://github.com/iovisor/bcc
.PP
Also look in the bcc distribution for a companion _examples.txt file containing
example usage, output, and commentary for this tool.
.SH OS
Linux
.SH STABILITY
Unstable - in development.
.SH AUTHOR
Sasha Goldshtein
.SH SEE ALSO
dbslower(8)