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# MySQL Performance and Administration Guide for DevOps
This document covers essential MySQL configuration parameters, monitoring practices, data integrity checks, slow query tuning, and useful command-line tools for database administration.
## Table of Contents
- [MySQL Performance and Administration Guide for DevOps](#mysql-performance-and-administration-guide-for-devops)
- [Table of Contents](#table-of-contents)
- [Configuration Parameters](#configuration-parameters)
- [max\_allowed\_packet](#max_allowed_packet)
- [Error and Slow Query Logs](#error-and-slow-query-logs)
- [skip\_name\_resolve](#skip_name_resolve)
- [Initial Root Password and Access Control](#initial-root-password-and-access-control)
- [Monitoring](#monitoring)
- [Performance Schema and Information Schema](#performance-schema-and-information-schema)
- [Percona Monitoring and Management (PMM)](#percona-monitoring-and-management-pmm)
- [Data Corruption Checking](#data-corruption-checking)
- [Slow Query Configuration Details](#slow-query-configuration-details)
- [Tools](#tools)
- [pt-stalk](#pt-stalk)
- [pt-diskstats](#pt-diskstats)
- [pt-summary](#pt-summary)
- [mysqlcheck](#mysqlcheck)
---
## Configuration Parameters
### max_allowed_packet
```ini
max_allowed_packet = 128M
```
- **Purpose**: Defines the maximum size of a single communication packet between the MySQL client and server.
- **Best Practice**: For large BLOB/ TEXT fields or large dumps, set to `1G`. Adjust according to workload and available memory.
### Error and Slow Query Logs
Place these directives under the `[mysqld]` section:
```ini
[mysqld]
log-error = /var/log/mysql/error.log
slow_query_log = 1
slow_query_log_file = /var/log/mysql/slow.log
```
- `log-error`: Location of the error log file.
- `slow_query_log`: Enables slow query logging.
- `slow_query_log_file`: Path to the slow query log file.
### skip_name_resolve
```ini
skip_name_resolve
```
- **Effect**: Disables resolution of client hostnames to IP addresses.
- **Benefit**: Improves connection speed and reduces DNS overhead. Use when all users connect via IP addresses or CIDR ranges.
---
## Initial Root Password and Access Control
After the first initialization of MySQL, the temporary root password is stored in `/var/log/mysqld.log`. Use it to log in and change the password.
**Change root password:**
```sql
ALTER USER 'root'@'%' IDENTIFIED BY '123';
```
**Restrict access to a specific IP or range** (e.g., 192.168.1.0/24):
```sql
ALTER USER 'root'@'192.168.1.0/24' IDENTIFIED BY '123';
```
> Replace `'123'` with a strong password and adjust the subnet as needed.
---
## Monitoring
### Performance Schema and Information Schema
MySQL provides two built-in schemas for monitoring:
- **performance_schema**: Tracks server execution details at a low level (waits, events, statements, etc.).
- **information_schema**: Provides metadata about database objects (tables, columns, privileges, etc.).
### Percona Monitoring and Management (PMM)
PMM is an open-source monitoring solution that integrates with **Grafana** for dashboards and visualization. It collects metrics from MySQL, PostgreSQL, MongoDB, and system hosts.
**Key features**:
- Query analytics and slow query tracking.
- Real‑time performance dashboards.
- Historical data retention.
**How to use**:
1. Install PMM Server (Docker or package) on a dedicated host.
2. Install PMM Client on each MySQL host.
3. Connect the client to the server:
`pmm-admin config --server-url=https://<pmm-server-ip>:443`
4. Add MySQL service:
`pmm-admin add mysql --username=root --password=<pwd>`
---
## Data Corruption Checking
Use `mysqlcheck` to verify table integrity.
**Check all databases:**
```bash
mysqlcheck --check --all-databases -u root -p
```
**Check a specific database:**
```bash
mysqlcheck --check <database_name> -u root -p
```
The command will report any corrupted tables. For deeper repair, use `--repair` after verifying the need.
---
## Slow Query Configuration Details
Extended slow query log configuration:
```ini
slow_query_log = 1
slow_query_log_file = /var/log/mysql/mysql-slow.log
long_query_time = 2
```
- `long_query_time`: Queries that take more than `2` seconds are logged. Fractional seconds allowed (e.g., `0.5`).
- Additional useful parameters:
- `log_queries_not_using_indexes = 1` – logs queries that do not utilise indexes.
- `log_slow_admin_statements = 1` – logs slow administrative statements (OPTIMIZE, ANALYZE, ALTER).
After changes, restart MySQL: `sudo systemctl restart mysql`
---
## Tools
This section covers command-line tools from the **Percona Toolkit** (commonly used by DBAs and DevOps). The names in the original notes (`py-stals`, `py-disktats`, `pt-summery`) likely refer to `pt-stalk`, `pt-diskstats`, and `pt-summary`.
### pt-stalk
**Description**: Watches for a MySQL problem (e.g., high load, long lock wait) and collects diagnostic data when the problem occurs.
**Installation** (Ubuntu/Debian):
```bash
sudo apt-get install percona-toolkit
```
**Basic usage**:
```bash
pt-stalk --user=root --password=<pwd> --dest=/var/log/pt-stalk -- --defaults-file=/etc/mysql/my.cnf
```
- `--user`, `--password`: MySQL credentials.
- `--dest`: Directory where collected data will be stored.
- The `--` separates pt-stalk options from MySQL options.
- By default, the script runs as a daemon. Use `--run-time=30s` for a single collection cycle.
**How to use**:
1. Configure thresholds (disk free, processlist size, etc.) to trigger data collection.
2. Review collected files (tarballs) after an incident to diagnose root causes.
### pt-diskstats
**Description**: Analyzes disk I/O performance interactively, similar to `iostat`, but with more detailed per‑device statistics and latency histograms.
**Basic usage**:
```bash
pt-diskstats --interval=5 --iterations=10
```
- `--interval`: Seconds between samples.
- `--iterations`: Number of samples (omit for infinite).
- You can specify devices: `pt-diskstats --devices=sda,sdb`
**How to use**:
- Monitor disk latency and IOPS in real time to identify storage bottlenecks for MySQL.
- Redirect output to a file for later analysis: `pt-diskstats --interval=2 > /tmp/io.log`.
### pt-summary
**Description**: Collects and prints a system overview – CPU, memory, disk, network, and MySQL configuration.
**Basic usage**:
```bash
pt-summary
```
**How to use**:
- Run before and after changes to capture baseline system state.
- Combine with `pt-mysql-summary` for MySQL‑specific detail.
- The output helps quickly understand the environment when debugging performance issues.
### mysqlcheck
Already covered in the [Data Corruption Checking](#data-corruption-checking) section.