How to fix ERR max number of clients reached in Redis

Connect to Redis and view the current limit:

redis-cli config get maxclients

This will show your current setting. The default is 10,000.

Increase the limit at runtime using:

redis-cli config set maxclients 50000

Replace 50000 with your desired limit. This takes effect immediately but will not persist after Redis restart.

Edit your Redis configuration file (usually /etc/redis/redis.conf) and find the maxclients directive:

maxclients 50000

Uncomment or modify the line to your desired value, then save the file.

Redis needs sufficient file descriptors at the OS level. Check and increase the limit:

ulimit -n
ulimit -Sn 100000

For permanent changes, edit /etc/systemd/system/redis.service:

[Service]
LimitNOFILE=100000

Then reload and restart:

sudo systemctl daemon-reload
sudo systemctl restart redis

After editing redis.conf, restart the Redis service:

sudo systemctl restart redis

Or if using Docker:

docker restart <container_id>

Review your application code for missing connection cleanup. Ensure all Redis connections are properly closed:

Node.js/TypeScript:

const redis = require('redis');
const client = redis.createClient();

try {
  // Use client
} finally {
  await client.quit(); // Explicitly close
}

Python:

import redis
client = redis.Redis()
try:
    # Use client
finally:
    client.close()

Go:

client := redis.NewClient(&redis.Options{Addr: "localhost:6379"})
defer client.Close()

Use connection pooling to reuse connections instead of creating new ones:

Node.js with redis-pool:

const pool = new Pool({
  max: 20,
  min: 5,
  idleTimeoutMillis: 30000
});

Python with redis-py:

from redis import ConnectionPool, Redis
pool = ConnectionPool.from_url('redis://localhost')
client = Redis(connection_pool=pool)