Identify why Google app engine is slow

Question

I developed an application for client that uses Play framework 1.x and runs on GAE. The app works great, but sometimes is crazy slow. It takes around 30 seconds to load simp

Answer 1

Combining some answers and adding a few things to check:

1. Debug using app stats. Look for "staircase" situations and RPC calls. Maybe something in your app is triggering RPC calls at certain points that don't happen in your logic all the time.

2. Tweak your instance settings. Add some permanent/resident instances and see if that makes a difference. If you are spinning up new instances, things will be slow, for probably around the time frame (30 seconds or more) you describe. It will seem random. It's not just how many instances, but what combinations of the sliders you are using (you can actually hurt yourself with too little/many).

3. Look at your app itself. Are you doing lots of memory allocations in the JVM? Allocating/freeing memory is inherently a slow operation and can cause freezes. Are you sure your freezing is not a JVM issue? Try replicating the problem locally and tweak the JVM xmx and xms settings and see if you find similar behavior. Also profile your application locally for memory/performance issues. You can cut down on allocations using pooling, DI containers, etc.

4. Are you running any sort of cron jobs/processing on your front-end servers? Try to move as much as you can to background tasks such as sending emails. The intervals may seem random, but it can be a result of things happening depending on your job settings. 9 am every day may not mean what you think depending on the cron/task options. A corollary - move things to back-end servers and pull queues.

It's tough to give you a good answer without more information. The best someone here can do is give you a starting point, which pretty much every answer here already has.