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