How can I resolve ActiveRecord::ConnectionTimeoutError in a Ruby on Rails application?

Resolving ActiveRecord::ConnectionTimeoutError in Rails

The ActiveRecord::ConnectionTimeoutError occurs in a Ruby on Rails application when the database connection pool is exhausted. This can happen due to long-running queries, insufficient connection pool size, or unclosed connections. Here are the steps to resolve this issue.

1. Increase Connection Pool Size

Cause: The connection pool size is too small to handle the number of concurrent database connections.

Fix: Increase the connection pool size in the config/database.yml file. Adjust the pool setting under your environment (e.g., development, production).

production:
  adapter: postgresql
  encoding: unicode
  pool: 10
  username: your_username
  password: your_password
  database: your_database

2. Optimize Database Queries

Cause: Long-running or inefficient queries can hold onto database connections for too long.

Fix: Optimize your database queries to be more efficient. Use indexes, avoid unnecessary joins, and use query optimization techniques to reduce query execution time.

3. Ensure Connections are Closed

Cause: Connections are not being properly closed, leading to a buildup of open connections.

Fix: Ensure that connections are properly closed after they are no longer needed. This is typically handled by Rails, but custom database connections should be explicitly closed.

4. Monitor and Scale

Cause: High traffic or increased load on the application causing more connections than the pool can handle.

Fix: Monitor your application's database connection usage and scale your infrastructure accordingly. Use tools like New Relic, Datadog, or custom monitoring solutions to track and manage database connections.

5. Use Connection Pool Management

Cause: Inefficient connection pool management.

Fix: Use gems or libraries that help manage the connection pool more efficiently. For example, the connection_pool gem can help manage and reuse connections effectively.

Additional Resources

For more detailed guidance, check out these resources: