A Note About keepAlive in Mongoose | Rustcode

A Note About keepAlive in Mongoose

Before Mongoose version 5.2.0, enabling the keepAlive option in the MongoDB connection was necessary to initiate TCP keepalive messages. These messages help prevent connections from being closed prematurely due to network inactivity, which can cause errors like "connection closed".

Changes in KeepAlive Behavior

Since Mongoose 5.2.0, keepAlive has been enabled by default, significantly reducing the need for manual setting. Furthermore, as of Mongoose version 7.2.0, the keepAlive option and its associated keepAliveInitialDelay option have been deprecated. It is now recommended to remove these options from your connection configurations to avoid confusion and potential deprecation warnings.

What Does keepAlive Do?

The keepAlive option sends periodic TCP keepalive packets on the socket to maintain the connection to MongoDB even during periods of inactivity. This helps prevent the connection from being closed by network intermediaries like routers or firewalls due to inactivity timeouts.

Modern Mongoose Connection Setup

With recent Mongoose versions, you don’t need to specify keepAlive explicitly. The MongoDB driver and Mongoose handle keepalive internally for you.

mongoose.connect('mongodb://localhost:27017/mydb', {
  useNewUrlParser: true,
  useUnifiedTopology: true
});

Advice for Long Running Applications

Long-running applications, such as web servers or real-time APIs, benefit from persistent connections. The built-in keepalive mechanisms ensure stable connections without the need for manual keepAlive configuration.

Summary Table

Option	Status	Notes
`keepAlive`	Enabled by default since Mongoose 5.2.0	Deprecated as of Mongoose 7.2.0; no manual setting needed
`keepAliveInitialDelay`	Was configurable for initial delay	Also deprecated with keepAlive option

Best Practices

Remove keepAlive and keepAliveInitialDelay from your connection options if you are using Mongoose 7.2.0 or later.
Rely on the MongoDB driver’s default TCP keepalive behavior for connection stability.
Monitor application logs for connection issues unrelated to keepalive configuration.

Conclusion

The keepAlive option was once critical for maintaining MongoDB connections but has been managed automatically by Mongoose in recent versions. Understanding this evolution helps you keep your Node.js apps clean and up-to-date with modern best practices.