MySQL Capture

A simple tool for capturing MySQL/MariaDB state information at regular intervals. Useful for troubleshooting performance issues or investigating incidents after the fact.

What it does

Connects to your MySQL database and continuously captures:

• Process list
• InnoDB engine status
• RocksDB engine status (when the engine is available)
• Global status variables

Everything gets written to compressed, hourly-rotated log files organized by date.

Database Permissions

Your database user needs the PROCESS privilege:

GRANT PROCESS ON *.* TO 'monitor'@'localhost';

PROCESS is required to see other users' threads in the process list and to run SHOW ENGINE <engine> STATUS commands.

Building

make

Two environment variables can be overridden:

Variable	Default	Description
GOARCH	host arch	Target architecture for cross-compilation (e.g. amd64, arm64)
CGO_ENABLED	1	Set to 0 to produce a fully static binary

Example:

CGO_ENABLED=0 GOARCH=arm64 make

Quick Start

Run:

# Connect and start capturing (default: 5 second intervals)
./capture --username monitor --ask-pass

# Specify output directory and interval
./capture --username monitor --password secret --path ./logs --interval 10s

Press Ctrl+C to stop.

Connection Options

Connect via TCP:

./capture --hostname 192.168.1.100 --port 3306 --username monitor --password secret

Connect via Unix socket (default for localhost):

./capture --username monitor --ask-pass

Use a MySQL config file:

./capture --defaults-file ~/.my.cnf

Output

Files are organized like this:

logs/
└── 20260216/
    ├── innodb.202602161500.gz
    ├── processlist.202602161500.gz
    └── status.202602161500.gz

A new file is started every hour, and the name holds the date and time of the hour it covers.

Each file contains timestamped snapshots that you can analyze later:

zcat logs/20260216/processlist.*.gz | grep "SELECT"

Retention

Old logs are kept until you delete them. Use --retention to delete them automatically:

./capture --username monitor --ask-pass --path ./logs --retention 168h

The check runs at start and then once an hour. It deletes capture files that are older than the given duration, and removes the date directory once it is empty. A directory that holds other files is kept. The shortest retention is 1 hour.