Configuration

This section explains Kronos configuration.

Scheduler Configuration

Scheduler configuration is defined in scheduler.yaml file and is picked by the Kronos from classpath to initialize and start the scheduler.

Task Definition Reader

The user can define custom reader to read task definitions from an external source. The user can define multiple task definition readers. The task definition readers are configured in the scheduler.yaml file under taskReaderConfig section. The user can also define a custom reader.

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
readerClass	fully qualified class name of the TaskDefinitionReader implementation	string	None	yes
schedule	A cron schedule to refresh the task definitions from the source	string	None	yes
config	additional configuration required by the reader during instantiation	objectnode	None	no

Sample configuration

taskReaderConfig:
  # name to be assigned to the reader
  filereader:
    # fully qualified classname of the TaskDefinitionReader.java implementation
    readerClass: com.cognitree.kronos.scheduler.readers.FileTaskDefinitionReader
    # additional configuration
    config:
      source: task-definitions.yaml
    # interval in cron to look for changes in the task definition file
    schedule: 0 0/1 * 1/1 * ? *

In the above sample, a file reader is configured.

Task Execution Config

A set of configuration required by scheduler per task type, defines max execution time and policy to apply on task in case of timeout.

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
maxExecutionTime	max allowed time for the task to finish execution if not explicitly specified by task	string	1d	no
timeoutPolicy	policy to apply in case of timeout if not explicitly specified by task	string	None	no

taskExecutionConfig:
  # task type
  shellCommand:
    # max execution time per task
    maxExecutionTime: 10m
    # policy to apply on task in case of timeout
    timeoutPolicy: notifyOnTimeout

In the above sample, max exection time is set to 10m and a notifyOnTimeout policy is configured for task type shellCommand. The above configuration is applied on all task of type shellCommand if not explicitly configured at a task level. Check out Task Definition section for more details.

Task Store

A task store is used to store the current state of the Kronos application. A task store is configured in the scheduler.yaml file under storeProvider section. The user can provide a custom implementation of task store.

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
taskStoreClass	fully qualified class name of the TaskStore implementation	string	None	yes
config	additional configuration required by the task store during instantiation	objectnode	None	no

taskStoreConfig:
  taskStoreClass: com.cognitree.kronos.store.SQLiteTaskStore
  config:
    connectionURL: jdbc:sqlite:kronos.db
    username:
    password:

In the above sample, a sqlite task store is configured.

Timeout Policy

Define policies to apply in case of task timeout. A timeout policy is configured in the scheduler.yaml file under timeoutPolicyConfig section. The user can provide implementation of timeout policy.

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
policyClass	fully qualified class name of the TimeoutPolicy implementation	string	None	yes
config	additional configuration required by the timeout policy during instantiation	objectnode	None	no

timeoutPolicyConfig:
  notifyOnTimeout:
    policyClass: com.cognitree.examples.tasks.scheduler.policies.NotifyOnTimeoutPolicy
    config:
      smtp.host: "smtp.gmail.com"
      smtp.port: 587
      sender.name:
      sender.email:
      sender.password:
      email.subject: "Task Timeout notification"
      recipient.name:
      recipient.email:

In the above sample, notifyOnTimeout is the policy identifier that is to be used while defining the task definition and/or task handler as the timeout policy.

Task Purge Interval

Periodically, tasks older than the specified interval and status in one of the final state are purged from memory. The task purge interval is configured in the scheduler.yaml file under taskPurgeInterval section.

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
taskPurgeInterval	purge interval (1d, 1h 15m etc)	string	1d	no

taskPurgeInterval: 6h

In the above sample, the task purge interval period is configured as 6 hours.

Executor

Executor configuration is defined in executor.yaml file and is picked by the Kronos from classpath to initialize and start the executor.

Task Handler

For each type of task, a handler needs to be configured to execute the task. A handler is configured in the executor.yaml file under handlerConfig section. The user can also define a custom handler.

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
handlerClass	fully qualified class name of the TaskHandler implementation	string	None	yes
config	additional configuration required by the handler during instantiation	objectnode	None	no
maxParallelTasks	max number of tasks allowed to be executed in parallel	string	max cores/2	no

# configure task handlers
taskHandlerConfig:
  # type of task to be handled by handler
  shellCommand:
    # handler implementation used to handle task of type shellCommand
    handlerClass: com.cognitree.kronos.executor.handlers.ShellCommandHandler
    # max parallel tasks handler is allowed to execute at any point of time
    maxParallelTasks: 4

In the above sample, Shell Command Handler is configured to handle tasks of type shellCommand.

Queue

Queue is used by the scheduler and executor to exchange messages. A producer and a consumer for the queue is to be configured in queue.yaml. The user can provide a custom implementation of queue.

Producer

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
producerClass	fully qualified class name of the Producer implementation	string	None	yes
config	additional configuration required by the producer during instantiation	objectnode	None	no

Consumer

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
consumerClass	fully qualified class name of the Consumer implementation	string	None	yes
config	additional configuration required by the consumer during instantiation	objectnode	None	no

# configure producer and consumer for the queue
producerConfig:
  producerClass: com.cognitree.kronos.queue.producer.InMemoryProducer
consumerConfig:
  consumerClass: com.cognitree.kronos.queue.consumer.InMemoryConsumer
  pollInterval: 100
# topic to use to publish task status reported by executor and consumed by scheduler
taskStatusQueue: taskstatus

In the above sample, an in-memory queue is configured.