The middle manager node is a worker node that executes submitted tasks. Middle Managers forward tasks to peons that run in separate JVMs. The reason we have separate JVMs for tasks is for log isolation. Each Peon is capable of running only one task at a time, however, a middle manager may have multiple peons.
io.druid.cli.Main server middleManager
With the following JVM configuration:
-Duser.timezone=UTC -Dfile.encoding=UTF-8 -Ddruid.host=localhost -Ddruid.port=8091 -Ddruid.service=middleManager -Ddruid.zk.service.host=localhost -Ddruid.db.connector.connectURI=jdbc:mysql://localhost:3306/druid -Ddruid.db.connector.user=druid -Ddruid.db.connector.password=diurd -Ddruid.selectors.indexing.serviceName=overlord -Ddruid.indexer.runner.startPort=8092 -Ddruid.indexer.fork.property.druid.computation.buffer.size=268435456
Middle managers pass their configurations down to their child peons. The middle manager module requires the following configs:
| Property | Description | Default |
|---|---|---|
druid.worker.ip | The IP of the worker. | localhost |
druid.worker.version | Version identifier for the middle manager. | 0 |
druid.worker.capacity | Maximum number of tasks the middle manager can accept. | Number of available processors - 1 |
druid.indexer.runner.compressZnodes | Indicates whether or not the middle managers should compress Znodes. | false |
druid.indexer.runner.maxZnodeBytes | The maximum size Znode in bytes that can be created in Zookeeper. | 524288 |
druid.indexer.runner.taskDir | Temporary intermediate directory used during task execution. | /tmp/persistent |
druid.indexer.runner.javaCommand | Command required to execute java. | java |
druid.indexer.runner.javaOpts | -X Java options to run the peon in its own JVM. | "" |
druid.indexer.runner.classpath | Java classpath for the peon. | System.getProperty(“java.class.path”) |
druid.indexer.runner.startPort | The port that peons begin running on. | 8080 |
druid.indexer.runner.allowedPrefixes | Whitelist of prefixes for configs that can be passed down to child peons. | “com.metamx”, “druid”, “io.druid”, “user.timezone”,“file.encoding” |