tasksmith

A task automation workflow library for node.

task.series([
  task.shell("ping google.com"),
  task.shell("echo hello"),
  task.shell("echo world"),
  task.shell("npm install express")
]).run(task.debug)

overview

tasksmith is a control flow automation library for node built to help automate running command line processes in scenarios where workflows need to be executed in a sophisticated, potentially non linear fashion. tasksmith focuses on achieving this through various control flow constructs (series/parallel/loop/repeat/retry/trycatch/ifelse/etc) and supports both sequential and parallel execution of processes. tasksmith provides a number of looping constructs, task cancellation, delay / deferral and conditional branching, all of which composable through tasksmiths various task abstractions.

tasksmith tasks

The following table lists all the tasks built into tasksmith.

task	signature	description
task.cli	(argv:string[], options: {[name: string]: Task}) => Task	creates a task that provides a simple cli to run tasks from the command line
task.create	(name: string, (context: Context) => void) => Task	creates a user defined task.
task.delay	(ms: number, () => Task) => Task	creates a task that delays for the given number of milliseconds.
task.each	(elements: Array<T>, func: (element: T) => Task) : Task	creates a repeating task that enumerates each element in the given sequence.
task.fail	(reason:string) => Task	creates a task that fails immediately.
task.ifelse	(() => boolean, () => Task, () => Task)=> Task	creates a task that runs the left or right task based on a condition.
task.noop	() => Task	creates a noop task. same as task.core.ok() task.
task.ok	() => Task	creates a task that succeeds immediately.
task.parallel	(() => Array<Task>) => Task	creates a inner task runs its inner tasks in parallel.
task.repeat	(iterations: number, () => Task) => Task	creates a task that repeats for the given number of iterations.
task.retry	(attempts: number, () => Task) => Task	creates a task that retries up to the given number of attempts.
task.series	(() => Array<Task>) => Task	creates a task that runs its inner tasks in series.
task.shell	(command: string, exitcode: number): Task	runs the given shell command with the given expected exitcode.
task.timeout	(ms: number, () => Task) => Task	creates a task that fails if its inner task has not completed within the given millisecond timeout.
task.trycatch	(() => Task, () => Task) => Task	creates a task that attempts the left task, and defers to the right task on fail.
task.watch	(path: string, () => Task) => Task	creates a task that repeats its inner task on file system watch events.
task.file.append	(target: string, content: string) => Task	creates a task that appends the target file with the given content.
task.file.concat	(output: string, inputs: Array<string>) => Task	creates a task that concatinates the given input paths into the output path.
task.file.copy	(source: string, target: string) => Task	creates a task that copies the source file into the target directory.
task.file.create	(target: string) => Task	creates a task that creates the target file if it doesn't exist.
task.file.drop	(target: string) => Task	creates a task that deletes the target file if it exists.
task.file.move	(source: string, target: string) => Task	creates a task that moves the given source file into the given target directory.
task.file.read	(target: string, func: (content: string) => Task): Task	reads the given target and returns its contents.
task.file.rename	(target: string, newname: string): Task	creates a task that renames the given target file to the given new name.
task.file.replaceText	(target: string, token: string, replacement: string) => Task	creates a task that runs a token replacement for the given file.
task.file.truncate	(target: string, content: string): Task	creates a task that truncates the target file and writes the given content. if the target
task.folder.copy	(source: string, target: string) => Task	creates a task that copies the source directory into the target.
task.folder.create	(target: string) => Task	creates a task that creates the target directory if not exists.
task.folder.drop	(target: string) => Task	creates a task that deletes the target directory if not exists.
task.folder.merge	(source: string, target: string): Task	merges the contents from the source directory into the target directory.
task.folder.move	(source: string, target: string): Task	creates a task that moves the given source directory into the the given target directory.
task.folder.rename	(target: string, newname: string) => Task	creates a task that renames the target directory.
task.http.get	(endpoint: string, func: (content: string) => Task): Task	creates a task that gets the http content from the remote endpoint.

running tasks

To run a task, call a tasks run() method. this method returns a Promise which the caller can use to learn of the success or failure of the task. The run() method accepts a function to receive logging information from the task.

let mytask = () => task.ok()

mytask.run(console.log)
  .then(() => {...})
  .catch(e => {...})

debugging tasks

tasksmith tasks may emit a wealth of information about task. This information can be useful for debugging tasks, however by default, the logging information is emitted in a unformatted fashion which may become confusing for complex tasks. As such, tasksmith provides a debugging function available with task.debug which can be passed to the tasks run function.

let mytask = () => task.ok()

mytask.run(task.debug) // 
  .then(() => {...})
  .catch(e => {...})

cancelling tasks

tasksmith tasks support cancellation through a tasks cancel() method. task cancellation is non trivial in javascript, and some tasks may or may not be cancellable. In tasksmith, a call to cancel is a signal into the running task that the caller intended to cancel, but the task may or may not choose to honor that request for cancellation. Instances of tasks that may not cancel are tasks that complete synchronously, or complete immediately. In addition, task cancellation does not involve rollback. As a general rule, a user can expect a task to terminate gracefully on cancel().

let mytask = () => task.series(() => [
  task.delay(1000, () => task.file.create("./file1.dat")), // 1 second
  task.delay(1000, () => task.file.create("./file2.dat")), // 2 second
  task.delay(1000, () => task.file.create("./file3.dat")), // 3 second
])

task.run()

// may have created some files along the way.

task.cancel()

user defined tasks

user defined tasks can be created in the following way. note that the first parameter is used to scope the task with a given name, the convention type/action is used but not required. The create() function also takes a handler function which is passed a context for fulfilling this task, detailed below.

let mytask = () => task.create("custom/mytask", context => {
  //------------------------------------------------------------
  // context.ok()          - completes this task.
  // context.fail()        - fails this task.
  // context.log(message)  - logs a message for this task. 
  // context.abort(handle) - handles a signal for cancellation.
  //------------------------------------------------------------

  context.ok()

  context.abort(() => {
    // clean up the task.
    context.fail()
  })
})

The abort() function is optional and may be ignored if the task doesn't support cancellation, however if implementing cancellation, the task should clean up any resources created by the task and either ok() or fail() the task. Note, that the abort() function will only be called once, and only if the task is in a non completed or running state.

license

MIT