A Minion is a standby component that leverages the Helix Task Framework to offload computationally intensive tasks from other components.
It can be attached to an existing Pinot cluster and then execute tasks as provided by the controller. Custom tasks can be plugged via annotations into the cluster. Some typical minion tasks are:
Segment creation
Segment purge
Segment merge
Starting a Minion
Make sure you've . If you're using docker, make sure to . To start a minion
Interfaces
PinotTaskGenerator
PinotTaskGenerator interface defines the APIs for the controller to generate tasks for minions to execute.
PinotTaskExecutorFactory
Factory for PinotTaskExecutor which defines the APIs for Minion to execute the tasks.
MinionEventObserverFactory
Factory for MinionEventObserver which defines the APIs for task event callbacks on minion.
Built-in Tasks
SegmentGenerationAndPushTask
To be added
RealtimeToOfflineSegmentsTask
See for details.
MergeRollupTask
See for details.
ConvertToRawIndexTask
To be added
Enable Tasks
Tasks are enabled on a per-table basis. To enable a certain task type (e.g. myTask) on a table, update the table config to include the task type:
Under each enable task type, custom properties can be configured for the task type.
Schedule Tasks
Auto-Schedule
Tasks can be scheduled periodically for all task types on all enabled tables. Enable auto task scheduling by configuring the schedule frequency in the controller config with the key controller.task.frequencyInSeconds.
Tasks can also be scheduled based on cron expressions. The cron expression is set in the schedule config for each task type separately. Thie optioncontroller.task.scheduler.enabled should be set to true to enable cron scheduling.
As shown below, the RealtimeToOfflineSegmentsTask will be scheduled at the first second of every minute (following the syntax ).
Manual Schedule
Tasks can be manually scheduled using the following controller rest APIs:
Rest API
Description
Plug-in Custom Tasks
To plug in a custom task, implement PinotTaskGenerator, PinotTaskExecutorFactory and MinionEventObserverFactory (optional) for the task type (all of them should return the same string for getTaskType()), and annotate them with the following annotations:
Implementation
Annotation
After annotating the classes, put them under the package of name org.apache.pinot.*.plugin.minion.tasks.*, then they will be auto-registered by the controller and minion.
Example
See where the TestTask is plugged-in.
Task-related metrics
There is a controller job that runs every 5 minutes by default and emits metrics about Minion tasks scheduled in Pinot. The following metrics are emitted for each task type:
NumMinionTasksInProgress: Number of running tasks
NumMinionSubtasksRunning: Number of running sub-tasks
NumMinionSubtasksWaiting: Number of waiting sub-tasks (unassigned to a minion as yet)
For each task, the Minion will emit these metrics:
TASK_QUEUEING: Task queueing time (task_dequeue_time - task_inqueue_time), assuming the time drift between helix controller and pinot minion is minor, otherwise the value may be negative
TASK_EXECUTION: Task execution time, which is the time spent on executing the task
NUMBER_OF_TASKS: number of tasks in progress on that minion. Whenever a Minion starts a task, increase the Gauge by 1, whenever a Minion completes (either succeeded or failed) a task, decrease it by 1
NumMinionSubtasksError: Number of error sub-tasks (completed with an error/exception)
PercentMinionSubtasksInQueue: Percent of sub-tasks in waiting or running states
PercentMinionSubtasksInError: Percent of sub-tasks in error
POST /tasks/schedule
Schedule tasks for all task types on all enabled tables
POST /tasks/schedule?taskType=myTask
Schedule tasks for the given task type on all enabled tables
POST /tasks/schedule?tableName=myTable_OFFLINE
Schedule tasks for all task types on the given table
POST /tasks/schedule?taskType=myTask&tableName=myTable_OFFLINE
Schedule tasks for the given task type on the given table
Usage: StartMinion
-help : Print this message. (required=false)
-minionHost <String> : Host name for minion. (required=false)
-minionPort <int> : Port number to start the minion at. (required=false)
-zkAddress <http> : HTTP address of Zookeeper. (required=false)
-clusterName <String> : Pinot cluster name. (required=false)
-configFileName <Config File Name> : Minion Starter Config file. (required=false)
public interface PinotTaskGenerator {
/**
* Initializes the task generator.
*/
void init(ClusterInfoAccessor clusterInfoAccessor);
/**
* Returns the task type of the generator.
*/
String getTaskType();
/**
* Generates a list of tasks to schedule based on the given table configs.
*/
List<PinotTaskConfig> generateTasks(List<TableConfig> tableConfigs);
/**
* Returns the timeout in milliseconds for each task, 3600000 (1 hour) by default.
*/
default long getTaskTimeoutMs() {
return JobConfig.DEFAULT_TIMEOUT_PER_TASK;
}
/**
* Returns the maximum number of concurrent tasks allowed per instance, 1 by default.
*/
default int getNumConcurrentTasksPerInstance() {
return JobConfig.DEFAULT_NUM_CONCURRENT_TASKS_PER_INSTANCE;
}
/**
* Performs necessary cleanups (e.g. remove metrics) when the controller leadership changes.
*/
default void nonLeaderCleanUp() {
}
}
public interface PinotTaskExecutorFactory {
/**
* Initializes the task executor factory.
*/
void init(MinionTaskZkMetadataManager zkMetadataManager);
/**
* Returns the task type of the executor.
*/
String getTaskType();
/**
* Creates a new task executor.
*/
PinotTaskExecutor create();
}
public interface PinotTaskExecutor {
/**
* Executes the task based on the given task config and returns the execution result.
*/
Object executeTask(PinotTaskConfig pinotTaskConfig)
throws Exception;
/**
* Tries to cancel the task.
*/
void cancel();
}
public interface MinionEventObserverFactory {
/**
* Initializes the task executor factory.
*/
void init(MinionTaskZkMetadataManager zkMetadataManager);
/**
* Returns the task type of the event observer.
*/
String getTaskType();
/**
* Creates a new task event observer.
*/
MinionEventObserver create();
}
public interface MinionEventObserver {
/**
* Invoked when a minion task starts.
*
* @param pinotTaskConfig Pinot task config
*/
void notifyTaskStart(PinotTaskConfig pinotTaskConfig);
/**
* Invoked when a minion task succeeds.
*
* @param pinotTaskConfig Pinot task config
* @param executionResult Execution result
*/
void notifyTaskSuccess(PinotTaskConfig pinotTaskConfig, @Nullable Object executionResult);
/**
* Invoked when a minion task gets cancelled.
*
* @param pinotTaskConfig Pinot task config
*/
void notifyTaskCancelled(PinotTaskConfig pinotTaskConfig);
/**
* Invoked when a minion task encounters exception.
*
* @param pinotTaskConfig Pinot task config
* @param exception Exception encountered during execution
*/
void notifyTaskError(PinotTaskConfig pinotTaskConfig, Exception exception);
}
