NAME

dbslower - Trace MySQL/PostgreSQL server queries slower than a threshold.

SYNOPSIS

dbslower [-v] [-p PID [PID ...]] [-x PATH] [-m THRESHOLD] {mysql,postgres}

DESCRIPTION

This traces queries served by a MySQL or PostgreSQL server, and prints those that exceed a latency (query time) threshold. By default a threshold of 1 ms is used.

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. Alternatively, MySQL queries can be traced without the USDT support using the -x option.

Since this uses BPF, only the root user can use this tool.

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).

OPTIONS

-h Print usage message.

-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.
-x PATH: Path to MySQL binary. This option allow to MySQL queries even when USDT probes aren't enabled on the MySQL server.
-m THRESHOLD: Minimum query latency (duration) to trace, in milliseconds. Default is 1 ms.
{mysql,postgres}: The database engine to trace.

EXAMPLES

Trace MySQL server queries slower than 1 ms:: # dbslower mysql
Trace slower than 10 ms for PostgreSQL in process 408:: # dbslower postgres -p 408 -m 10

FIELDS

TIME(s): Time of query start, in seconds.
PID: Process ID of the traced server.
MS: Milliseconds for the query, from start to end.
QUERY: Query string, truncated to 256 characters.

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.

SOURCE

This is from bcc.

: https://github.com/iovisor/bcc

Also look in the bcc distribution for a companion _examples.txt file containing example usage, output, and commentary for this tool.

OS

Linux

STABILITY

Unstable - in development.

AUTHOR

Sasha Goldshtein, Brendan Gregg