The Code Style is available in XML format at [druid_intellij_formatting.xml](druid_intellij_formatting.xml) and can be [imported into IntelliJ](https://www.jetbrains.com/help/idea/2017.1/copying-code-style-settings.html).
The installation of a MySQL metadata store is outside the scope of this document, but instructions on setting up MySQL can be found at [docs/development/extensions-core/mysql.md](/docs/development/extensions-core/mysql.md). This assumes you followed the example there and have a database named `druid` with proper permissions for a user named `druid` and a password of `diurd`.
This also assumes you have [ZooKeeper](http://zookeeper.apache.org/releases.html) running locally, which usually just involves downloading the latest distribution of ZooKeeper, doing some minor configuration in ZooKeeper's `conf/` directory (most defaults are fine), then running `./bin/zkServer.sh start` in the ZooKeeper directory.
Before running or debugging the apps, you should do a `mvn clean install -Pdist -DskipTests` in the Druid source in order to make sure directories are populated correctly.
`-Pdist` is required because it puts all core extensions under `distribution\target\extensions` directory, where `runConfigurations` below could load extensions from.
You may also add `-Dweb.console.skip=true` to the command if you're focusing on backend servers instead of frontend project. This option saves great building time.
Intellij IDEA debugger can attach to a local or remote Java process (Druid process).
Follow these steps to debug a Druid process using the IntelliJ IDEA debugger.
1. Enable debugging in the Druid process
1. For Druid services (such as Overlord, Coordinator, etc), include the following as JVM config `-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=<PORT>` where `<PORT>` is any available port. Note that different port values should be chosen for each Druid service.
2. For the peons (workers on Middlemanager), include the following `agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=0` in runtime properties `druid.indexer.runner.javaOpts` of the Middle Manager. Note that `address=0` will tell the debugger to assign ephemeral port.
2. Find the port assigned to the Druid process.
1. For Druid services, the port value is what you chose in the JVM argument of step 1i above. The port value can also be found in the first line of each Druid service log.
2. For the peons (workers on Middlemanager), you can find the assigned ephemeral port by checking the first line of the task log.
3. Attach Intellij IDEA debugger to the running process
1. Create a Remote configuration in the Run/Debug Configurations dialog of Intellij (see: https://www.jetbrains.com/help/idea/tutorial-remote-debug.html#debugger_rc)
2. Set the port value using the value from step 2 for the Druid service and/or peon (worker on Middlemanager) that you want to debug
3. Start (debug) the above remote configuration
4. Repeat step 3i to 3iii for each Druid service and/or peon (worker on Middlemanager) that you want to debug
You can configure application definitions in XML for import into IntelliJ. Below are a few examples. These should be placed in an XML file in `.idea/runConfigurations` in the Druid source code.
For example, put a file named as `common.properties` under `.idea/conf` directory, then add `-Ddruid.properties.file=$PROJECT_DIR$/.idea/conf/common.properties` to `VM_PARAMETERS` in the App Def file.
