1. Guide

1.1. Mission

The goal of this project is to provide a high-performance and intuitive job scheduling framework in the Dart language ecosystem that anyone can use in the world.

And the development concept of this framework is “DRY“, “KISS” and “YAGNI“, which has been said in software engineering circles for a long time.

1.2. Features

• Easy and intuitive job scheduling.
• No complicated configuration files.
• Supports scheduling in Cron format.
• Supports powerful logging feature and it’s customizable.
• Supports easily define parallel processes.
• Supports conditional branching of jobs and steps.
• Supports extensive callback functions at each event.
• Supports skipping and retrying according to user defined conditions.

1.3. Getting Started

1.3.1. Install Library

 dart pub add batch

Note:
In Pub.dev, the automatic determination at the time of release of this library labels it as usable in Flutter, but it is not suitable by any stretch of the imagination.

1.3.2. Import

The following import will provide all the materials for developing job scheduling using Batch.dart.

import 'package:batch/batch.dart';

1.3.3. Basic Concept

Batch.dart represents the unit of scheduled processing as an Event.
And Event is composed of the following elements.

	Description
Job	This Job event is a unit of batch processing in the broad sense. And Job has multiple Step events.
ScheduledJob	It represents a scheduled job. And ScheduledJob has multiple Step events.
Step	This event expresses the sequential processing. Each Step has a Task that defines one specific process.
ParallelStep	This event expresses the parallel processing. Each ParallelStep has ParallelTasks that define specific processes.

1.3.4. Schedule Jobs

1.3.4.1. Sequential Process

When defining a simple sequential process, all that is required is to define a class that extends Task and implements the execute method.

It is also easy to define a scheduled job: define a process to generate a ScheduledJob in a class that implements ScheduledJobBuilder and pass it to the jobs argument of BatchApplication.

Example

import 'package:batch/batch.dart';

void main() => BatchApplication(
      jobs: [SayHelloWorldJob()],
    )..run();


class SayHelloWorldJob implements ScheduledJobBuilder {
  @override
  ScheduledJob build() => ScheduledJob(
        name: 'Test Job',
        schedule: CronParser('*/2 * * * *'), // Execute every 2 minutes
        steps: [
          Step(
            name: 'Test Step',
            task: SayHelloWorldTask(),
          )
        ],
      );
}

class SayHelloWorldTask extends Task<SayHelloWorldTask> {
  @override
  void execute(ExecutionContext context) {
    log.info('Hello, World!');
  }
}

You can see more examples at Official Examples.

1.3.4.2. Parallel Process

Batch.dart supports powerful parallel processing and is easy to define.

When defining parallel processing, all you have to do is just inherit from ParallelTask and describe the process you want to parallelize in the execute method.

SharedParameters and JobParameters set in the main thread can be referenced through ExecutionContext. However, note that under the current specification, changes to the ExecutionContext value during parallel processing are not reflected in the main thread’s ExecutionContext.

Example

import 'dart:async';

import 'package:batch/batch.dart';

void main() => BatchApplication(
      jobs: [DoHeavyProcessJob()],
    )..run();

class DoHeavyProcessJob implements ScheduledJobBuilder {
  @override
  ScheduledJob build() => ScheduledJob(
        name: 'Job',
        schedule: CronParser('*/2 * * * *'), // Execute every 2 minutes
        steps: [
          ParallelStep(
            name: 'Parallel Step',
            tasks: [
              DoHeavyTask(),
              DoHeavyTask(),
              DoHeavyTask(),
              DoHeavyTask(),
            ],
          )
        ],
      );
}


class DoHeavyTask extends ParallelTask<DoHeavyTask> {
  @override
  FutureOr<void> execute(ExecutionContext context) {
    int i = 0;
    while (i < 10000000000) {
      i++;
    }
  }
}

1.3.5. Logging

The Batch.dart provides the following well-known logging features as a standard.
And the default log level is trace.

• trace
• debug
• info
• warn
• error
• fatal

The logging feature provided by Batch.dart has extensive customization options. For more information, you can refer to the Official Documents describing logging on Batch.dart.

1.3.5.1. On Sequential Process

It’s very easy to use logging functions on sequential process.

The logging methods provided by the Batch.dart can be used from any class that imports batch.dart. So no need to instantiate any Loggers by yourself!

All you need to specify about logging in Batch.dart is the configuration of the log before run BatchApplication, and the Logger is provided safely under the lifecycle of the Batch.dart.

Example

import 'package:batch/batch.dart';

class TestLogTask extends Task<TestLogTask> {
  @override
  void execute() {
    log.trace('Test trace');
    log.debug('Test debug');
    log.info('Test info');
    log.warn('Test warning');
    log.error('Test error');
    log.fatal('Test fatal');
  }
}

For example, if you run example, you can get the following log output.

yyyy-MM-dd 19:25:10.575109 [info ] (_BatchApplication.run:129:11  ) - ??????? The batch process has started! ???????
yyyy-MM-dd 19:25:10.579318 [info ] (_BatchApplication.run:130:11  ) - Logger instance has completed loading
yyyy-MM-dd 19:25:10.580177 [info ] (_BootDiagnostics.run:32:9     ) - Batch application diagnostics have been started
yyyy-MM-dd 19:25:10.583234 [info ] (_BootDiagnostics.run:46:9     ) - Batch application diagnostics have been completed
yyyy-MM-dd 19:25:10.583344 [info ] (_BootDiagnostics.run:47:9     ) - Batch applications can be started securely
yyyy-MM-dd 19:25:10.585729 [info ] (JobScheduler.run:37:9         ) - Started Job scheduling on startup
yyyy-MM-dd 19:25:10.585921 [info ] (JobScheduler.run:38:9         ) - Detected 3 Jobs on the root
yyyy-MM-dd 19:25:10.586023 [info ] (JobScheduler.run:41:11        ) - Scheduling Job [name=Job1]
yyyy-MM-dd 19:25:10.595706 [info ] (JobScheduler.run:41:11        ) - Scheduling Job [name=Job2]
yyyy-MM-dd 19:25:10.597471 [info ] (JobScheduler.run:41:11        ) - Scheduling Job [name=Job4]
yyyy-MM-dd 19:25:10.597692 [info ] (JobScheduler.run:56:9         ) - Job scheduling has been completed and the batch application is now running

Note:
The setup of the logger is done when executing the method run in BatchApplication.
If you want to use the logging feature outside the life cycle of this library,
be sure to do so after executing the run method of the BatchApplication.

1.3.5.2. On Parallel Process

Parallel processing cannot directly use the convenient logging features described above. This is because parallel processing in the Dart language does not share any instances.

Instead, use the following methods in classes that extend ParallelTask for parallel processing.

• sendMessageAsTrace
• sendMessageAsDebug
• sendMessageAsInfo
• sendMessageAsWarn
• sendMessageAsError
• sendMessageAsFatal

Example

class TestParallelTask extends ParallelTask<TestParallelTask> {
  @override
  FutureOr<void> invoke() {
    super.sendMessageAsTrace('Trace');
    super.sendMessageAsDebug('Debug');
    super.sendMessageAsInfo('Info');
    super.sendMessageAsWarn('Warn');
    super.sendMessageAsError('Error');
    super.sendMessageAsFatal('Fatal');
  }
}

It should be noted that log output does not occur at the moment the above sendMessageAsX method is used.

This is only a function that simulates log output in parallel processing, and all messages are output at once when all parallel processing included in Parallel is completed.

And you can get the following log output from parallel processes.

yyyy-MM-dd 10:05:06.662561 [trace] (solatedLogMessage.output:36:13) - Received from the isolated thread [message=Trace]
yyyy-MM-dd 10:05:06.662666 [debug] (solatedLogMessage.output:39:13) - Received from the isolated thread [message=Debug]
yyyy-MM-dd 10:05:06.662760 [info ] (solatedLogMessage.output:42:13) - Received from the isolated thread [message=Info]
yyyy-MM-dd 10:05:06.662856 [warn ] (solatedLogMessage.output:45:13) - Received from the isolated thread [message=Warn]
yyyy-MM-dd 10:05:06.662947 [error] (solatedLogMessage.output:48:13) - Received from the isolated thread [message=Error]
yyyy-MM-dd 10:05:06.663039 [fatal] (solatedLogMessage.output:51:13) - Received from the isolated thread [message=Fatal]

1.3.6. Branch

Batch.dart supports conditional branching for each scheduled event (it’s just called “Branch” in Batch.dart).

Branch is designed to be derived from each event, such as Job and Step. There is no limit to the number of branches that can be set up, and a recursive nesting structure is also possible.

Creating a branch for each event is very easy.

To create branch

    Step(
      name: 'Step',
      task: SwitchBranchStatusTask(),

      // Each branch can be multiple and nested
      branchesOnSucceeded: [Step(name: 'Step on succeeded', task: doSomethingTask)],
      branchesOnFailed: [Step(name: 'Step on failed', task: doSomethingTask)],
      branchesOnCompleted: [Step(name: 'Step on completed', task: doSomethingTask)],
    );

And the conditional branching of Batch.dart is controlled by switching the BranchStatus of each Executions that can be referenced from the ExecutionContext.
The default branch status is “completed“.

To manage branch

class SwitchBranchStatusTask extends Task<SwitchBranchStatusTask> {
  @override
  void execute(ExecutionContext context) {
    // You can easily manage branch status through methods as below.
    context.jobExecution!.switchBranchToSucceeded();
    context.stepExecution!.switchBranchToFailed();
  }
}

1.4. More Examples

• Create a minimal and basic batch application
• Create a batch application consisting of multiple job nets
• Create a parallel processing tasks
• Pass command line arguments to batch application
• Create a branch and switch
• Use callback functions
• Define skippable exceptions
• Define retry processing

You can check more at Official Examples.

1.5. Contribution

If you would like to contribute to Batch.dart, please create an issue or create a Pull Request.

Owner will respond to issues and review pull requests as quickly as possible.

1.6. Support

The simplest way to show us your support is by giving the project a star at here.

And I’m always looking for sponsors to support this project. I’m not asking for royalties for use in providing this framework, but I do need support to continue ongoing open source development.

Sponsors can be individuals or corporations, and the amount is optional.

1.7. License

All resources of Batch.dart is provided under the BSD-3 license.

Note:
License notices in the source are strictly validated based on .github/header-checker-lint.yml. Please check header-checker-lint.yml for the permitted standards.

1.8. More Information

Batch.dart was designed and implemented by Kato Shinya.

• Creator Profile
• License
• API Document
• Official Documents
• Official Examples
• Wikipedia
• Release Note
• Bug Report