EC
3099
MySQLERRORNotableReplicationHIGH confidence

Incorrect or missing replication slave configuration

Production Risk

High — replication does not start until the configuration is corrected.

What this means

The replication slave is not properly configured. Required configuration options are missing or inconsistent.

Why it happens
  1. 1Missing MASTER_HOST, MASTER_USER, or MASTER_PASSWORD in CHANGE MASTER TO.
  2. 2Conflicting replication options (e.g., mixing GTID and file-based position).
How to reproduce
trigger — this will error
trigger — this will error
START SLAVE;  -- without CHANGE MASTER TO having been run

expected output

ERROR 3099 (HY000): Slave configuration error.

Fix

Run CHANGE MASTER TO with all required parameters

Run CHANGE MASTER TO with all required parameters
CHANGE MASTER TO
  MASTER_HOST='source_host',
  MASTER_USER='repl_user',
  MASTER_PASSWORD='repl_pass',
  MASTER_AUTO_POSITION=1;
START SLAVE;

Why this works

Provides all necessary configuration for replication to start.

What not to do

✕

Sources
Official documentation ↗

MySQL 8.0 — 3099 ER_SLAVE_CONFIGURATION2

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