Introduction

Elasticsearch is quite a cool project. This post introduces how to setup Elasticsearch in IntelliJ Idea locally. After this, we are able to :

• read Elasticsearch source code within an IDE
• debug Elasticsearch
• modify & develop new features of Elasticsearch

Solution

Step 1

clone the code from github (https://github.com/elastic/elasticsearch)

$> git clone git@github.com:elastic/elasticsearch.git

Step 2

make sure you have IntelliJ Idea installed locally. Now let’s setup Elasticsearch project.

New a project from existing sources.

Use Gradle as the package management tool. (ES 5.X, 6.X are using Gradle instead of Maven)

Check Use auto-import. The Gradle project directory should be yours accordingly. Next click Finish.

Step 3

The Elasticsearch project might contain multiple branches. The master branch requires latest version of Gradle, Java, etc. I checkout to 5.6 branch in my case, since my current environment looks good to 5.6 branch.

$> git checkout 5.6

Have a try using the Gradle wrapper. The following will create a distribution of Elasticsearch with the source code. It could take a long time for downloading dependencies & building source codes (70 minutes on my computer).

./gradlew assemble

This generates a ES distribution locally.

Step 4

Now let’s begin to run & debug Elasticsearch source code. Directly running Elasticsearch within IntelliJ Idea is possible, but requires more extra effort. Let’s adopt Elastic's advices.

Run Elasticsearch

Set up a real Elasticsearch instance with ./gradlew run --debug-jvm

elastic@:~/Documents/elasticsearch (5.6)$ ./gradlew run --debug-jvm
To honour the JVM settings for this build a new JVM will be forked. Please consider using the daemon: https://docs.gradle.org/4.3/userguide/gradle_daemon.html.
Daemon will be stopped at the end of the build stopping after processing

> Configure project :benchmarks 
...
Note: /Users/shun.ni/Documents/hulu/elasticsearch/modules/transport-netty4/src/main/java/org/elasticsearch/http/netty4/Netty4HttpChannel.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

[elasticsearch] Listening for transport dt_socket at address: 8000

> Task :distribution:run#start 
Running elasticsearch in debug mode, suspending until connected on port 8000

This instances listens to remote IDE in a certain port: 8000. Remember this port.

Debug Elasticsearch remotely

Then use IntelliJ Idea to debug this instance remotely.
Set up Idea, click Run -> Edit Configurations. Setup a Remote Debugging.

Click OK, then we get a new icon like this.

Click Debug 'ES_remote', then IntelliJ Idea connects to ES.

Verify the debugging

Set a breakpoint in OsInfo.java

Access the local ES Restful API with a browser: http://localhost:9200/_nodes This should collect all nodes’ info, and it will invoke toXContent method in OsInfo.java. The program should be paused right at that line (shown in the above picture).

Also you get the response of the RESTful API like this:

This is the start, now we are good to go. Read the source code & develop new features!

Reference

• https://github.com/elastic/elasticsearch/blob/master/TESTING.asciidoc#debugging-from-an-ide

Contact me

If you get any question, you are welcome to contact me via:

• email: nisxiya@yeah.net
• wechat: nisxiya