poc-java-dump-analysis

Some code samples to force errors - and then generate memory/thread dumps to analyse

Application

A simple Spring Boot REST App is provided with two endpoints

• doStore
• doThread

You can start the application by running make build then make run

** This requires java sdk 1.8 and mvn installed.

doStore

This endpoint adds a big map to in memory storage. Use make load-heap to run it.

doThread

This endpoint generates a big number (1000) of threads, sleeping for 1 minutes. Use make load-thread to run it. Running it a couple of times will provide enough number of threads!

Exploring the heap

Use make load-heap up to 5 times. This will use doStore endpoint, storing a relatively big amount of data in memory. Then, to generate a heap dump, use make heapdump This will generate a heapdump.hprof file that an be analysed by your favourite tool.

Use make heapdump-ci when using the ci (dockerized)version.This will generate a hprof file in your/tmpfolder. Note : be sure to chmod the resulting/tmp/heapdump.hprof` file so your user can read it.

Exploring the threads

Use make load-thread up to 3 times. This will use doThread endpoint, creating 1000 threads sleeping 1 minute each. Then, obtain thread dumps using make threaddump. This will generate threaddump_[1..5].tdump files you can analyse later.

Nice online tool : https://jstack.review/ you can upload multiple thread dump files, and compare in pairs.

Use make threaddump-ci when using the ci version. This will generate a .tdump file in your tmp folder.

CI

Travis-ci is used to demonstrate how this all works. It will use make ci , that includes:

• build app and docker container
• start container (naugthy slepp to wait for it to start, but hey, this works!)
• hit the doStore endpoint several times so there's some heap info available
• generate heap and thread dumps
• check (ls to the rescue) dump files are generated in /tmp folder

You can use make ci locally to quickly get some dumps to explore.