Goroutines in Google App Engine: Why are Long-Running Goroutines a Bad Idea?

Goroutines in Google App Engine: Limitations and Alternatives

In Google App Engine Standard Environment, goroutines are supported but with certain limitations. While the example you provided may seem to work, it's not recommended to use goroutines that outlive the request.

Why is it not safe?

Goroutines that continue to run after the request has finished can lead to memory leaks and resource starvation in the application instance. This is because the goroutine's lifetime is not tied to the request's lifecycle.

Alternative: runtime.RunInBackground

To execute code in a background goroutine safely, you can use the runtime.RunInBackground function. This function executes the provided function in a background context, which is distinct from the request's context.

<code class="go">func MyHandler(w http.ResponseWriter, r *http.Request) {

  err := runtime.RunInBackground(c, func(c appengine.Context) {
    // Do something...
  })

  // Return 200 status code
}</code>

Limitations of Runtime.RunInBackground

Note that there is a limit of 10 simultaneous background requests per instance. Exceeding this limit can cause performance issues or even application errors.

Goroutines within Request Context

Goroutines that live within the context of a request are supported. This means you can use goroutines to handle tasks that are part of the request's processing. However, these goroutines must finish before the request does.

Summary

While goroutines are supported in Google App Engine Standard Environment, it's important to be aware of the limitations. For safe and efficient background processing, use runtime.RunInBackground and ensure that background tasks complete before the request ends.

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