EC
2003
MySQLERRORCommonConnectionHIGH confidence

Too many connections for this user

Production Risk

High — application connections are refused.

What this means

The user account has reached the per-user connection limit set by MAX_USER_CONNECTIONS. New connections from this user are refused until existing ones are closed.

Why it happens
  1. 1MAX_USER_CONNECTIONS limit set on the user account has been reached.
  2. 2Connection pooling misconfiguration causing connection leaks.
  3. 3Application not closing connections after use.
How to reproduce
trigger — this will error
trigger — this will error
-- Occurs at connection time; check: SELECT * FROM information_schema.PROCESSLIST WHERE USER='app_user';

expected output

ERROR 2003 (HY000): User 'app_user' has exceeded the 'max_user_connections' resource (current value: 50).

Fix 1

Increase or remove the per-user connection limit

Increase or remove the per-user connection limit
ALTER USER 'app_user'@'%' WITH MAX_USER_CONNECTIONS 200;
-- Or remove: ALTER USER 'app_user'@'%' WITH MAX_USER_CONNECTIONS 0;

Why this works

Setting MAX_USER_CONNECTIONS to 0 removes the per-user limit (global limit still applies).

Fix 2

Fix connection leaks in the application

Fix connection leaks in the application
-- Ensure every connection is closed after use; use a connection pool

Why this works

Properly managed pools limit the number of simultaneous connections.

What not to do

✕

Version notes

Sources
Official documentation ↗

MySQL 8.0 — 2003 ER_TOO_MANY_USER_CONNECTIONS

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