Google App Engine /_ah/health

Question

I've set up my Node.js app to log any request that returns 404. Like this:

console.error("404: " + req.url);

Now when debugging other issue, I found out that my log is flooded with these:

404: /_ah/health
404: /_ah/health
404: /_ah/health

There are countless number of them and they aren't even 1ms apart.

What are they? Who sent them? Is it from GAE? Some sort of health check polling or something? Should I serve that URL? What should I serve in that URL?

Answer 1

Serve anything that returns a 200 response. It is health check polling. BTW, you can turn that off:

https://cloud.google.com/appengine/docs/flexible/nodejs/how-instances-are-managed

https://cloud.google.com/appengine/docs/flexible/nodejs/configuring-your-app-with-app-yaml#health_checks

Answer 2

For example when using nodejs with express you can do something like:

app.get('/_ah/health', function(req, res) {
  res.type('text').send('ok');
});