Nostradamus Predicting Maelstroms


    2.1.12 • Public • Published


    Why ?

    We have implemented the Task class in order to :

    1. construct scientific pipelines,
    2. manage data for scientific calculations (inputs and outputs),
    3. submit scientific jobs to a JM (= Job Manager, more info in the Job Manager section).

    What is a Task ?

    A Task is a class inherited from the Readable Stream class. Thus, it can contain data and do stuff with it. It can also use the method pipe like : mytask.pipe(writableStream) and transfer its data to a writable Stream. The output data is always in JSON format.

    What are Slots ?

    A Task contains Slots (mytask.myslot). These are objects inherited from the Writable Stream class. Thus, we can push data on them like : readableStream.pipe(mytask.myslot). Each input needed to run a Task calculation is associated to one unique Slot (so each Slot is created to receive only one unique input). As a consequence, a Task must have at least one Slot. The input data must be pushed in a JSON format.

    Construct pipelines

    Regarding the two previous parts, we can easily construct a pipeline :

    task_a.pipe(task_c.slot_1) // a -> c.1
    task_b.pipe(task_c.slot_2) // b -> c.2
    task_c.pipe(task_d.slot_1) // c -> d.1
    task_d.pipe(task_e.slot_1) // d -> e.1

    Here task_c contains two Slots : slot_1 and slot_2. The slot_1 takes data from task_a, and the slot_2 takes data from task_b. Then, task_c push its results into the slot_1 of task_d. Finally, results of task_d are pushed into the slot_1 of task_e.

    Note that even if the task_d has only one input, it is pushed on a Slot and not on the Task itself (same for task_e).

    If you want to learn more about pipelines, see our pipelineobject project (GitHub repo, NPM package).

    Remarks about Tasks

    • for the constistency of the pipeline, data exchanged between Tasks and Slots are in JSON format.
    • a Task depends on a JM to run the calculations.
    • a Task always provide a bash script (named CoreScript) that will be passed to the JM (with the inputs and the settings) to run the job. It is the core of the job.


    In your project repository :

    npm install taskobject

    Usage : tests

    This module can be used only with the test modes. In fact, the taskobject is an abstract class created as a base to implement bioinformatic tasks, using inheritance.
    Two test modes are available. Each one is based on a child class of the taskobject :

    • the simple test : uses the simpletask (more info in the SimpleTask section)
    • the dual test : uses the dualtask (more info in the DualTask section)
      You can either make a test in your proper JS file or use one of the test files we provide.

    Your proper test

    In your JS script, import the test file :

    var tkTest = require('./node_modules/taskobject/test/test');

    Then you have to start and set up a JM. We provide a method that takes care of that :


    JMsetup returns an object instance of EventEmitter. It emits "ready" when the JM is ready to receive jobs, and provide the JM object. Then, you can run the simpleTest method (or the dualTest method) :

    tkTest.JMsetup().on('ready', function (JMobject) {
        tkTest.simpleTest(inputFile, management);
        tkTest.dualTest(inputFile1, inputFile2, management);
    • inputFile are absolute path to your input file(s). No specific format needed.
    • management is a literal like :
    let management = {
        'jobManager' : JMobject // provided by the JMsetup method

    The simpleTest method :

    1. instantiates a simpletask (more info in the SimpleTask section),
    2. creates a stream (Readable) with your inputFile content (in a JSON),
    3. pipes the stream on the simpleTask.input slot,
    4. pipes the simpletask object on process.stdout, so you can watch the results in your console.

    The dualTest method :

    1. instantiates a dualtask (more info in the DualTask section),
    2. creates two streams (Readable) each one containing a JSON with an input content (inputFile1 and inputFile2),
    3. pipes the stream of inputFile1 on the simpleTask.input1 slot,
    4. pipes the stream of inputFile2 on the simpleTask.input2 slot,
    5. pipes the dualtask object on process.stdout, so you can watch the results in your console.

    The test file

    The previous tests are already implemented in the ./node_modules/taskobject/test/ directory. To use it :

    node ./node_modules/taskobject/test.js

    This script needs some command line options. You can use option -h to display the help.

    Task developer

    To read before beginning :

    • The development of a Task should be done in TypeScript. Here the examples are in TS, and are all related to each other.
    • Each task class must be developp as a unique NPM package.
    • The name of your class must be exactly the same as the name of your NPM package. You cannot choose a name with special characters or capital letters.
    • A Task object must be used for only one job. Each Task instance is meant to run once and can't be reused.

    Project initialization

    In your project directory :

    tsc --init # initialize a TS project (tsconfig.json) 
    npm init # say yes to all 
    npm install --save taskobject # we need the taskobject package 
    npm install --save-dev @types/node # in TS you need node types 

    Directory tree

    Your directories must be organized like the following directory tree :

    ├── data
    │   └──
    ├── index.js
    ├── node_modules
    │   ├── @types
    │   │   └── node
    │   └── taskobject
    ├── package.json
    ├── test
    │   └── test.js
    ├── ts
    │   └── src
    │       ├── index.ts
    │       ├── test
    │       │   └── test.ts
    │       └── types
    │           └── index.ts
    ├── tsconfig.json
    └── types
        └── index.js

    The tsconfig

        "compilerOptions": {
            "allowJs" : true,
            "baseUrl": ".",
            "lib": [ "dom", "es7" ],
            "listEmittedFiles" : true,
            "listFiles" : false,
            "maxNodeModuleJsDepth" : 10,
            "module": "commonjs",
            "moduleResolution" : "node",
            "outDir" : "./",
            "paths": {
                "*": [ "node_modules/" ]
            "preserveConstEnums" : true,
            "removeComments" : false,
            "target": "ES6"
        "files": [ // path to the files to compile

    The core script

    Every Task must have a bash script which runs the calculations. We named it the core script.

    In your core script, you can access to :

    1. the inputs you defined thanks to the Slots (in the slotSymbols array, see The constructor part),
    2. the modules you gave to the options literal (see Options Literal part),
    3. the variables you gave to the options literal (see Options Literal part).

    Warning : the standard output of the core script must be only JSON containing the results. Otherwise, your Task will crash.

    Example :

    # Take the content of myInputA : 
    contentInputA=`cat $myinputA` # (1) 
    # Run myModule1 with myInputB as a parameter : 
    myModule1 $myInputB > /dev/null # (2) 
    # Run myModule2 with the options : ' -ncpu 16 -file /path/toto.txt ' : 
    myModule2 $myVar_module2 > /dev/null # (3) 
    # Create the JSON as output : 
    echo "\"pathOfCurrentDir\" : \""
    echo $(pwd) # the path of the current directory 
    echo "\" }"

    Remark : the key used in the stdout JSON is important during the implementation of the method "prepareResults" (see the The methods to implement section).

    The task class

    In the current directory (see the Directory tree section), yous have to create a JavaScript file named index.js, where you will create your task class.

    Remark : do not forget to export your class !


    Your class must inherit from the taskobject (in TS you have to declare all the slots before writing the constructor) :

    import tk = require('taskobject');
    declare var __dirname; // mandatory
    class my_custom_task extends tk.Task {
        public readonly myInputA;
        public readonly myInputB;

    The constructor

    1. call the parent class constructor,
    2. take the current directory of your Task class,
    3. construct the path to the bash script of your Task with this.rootdir,
    4. define the Slot names of your Task, one for each input (in the slotSymbols array),
    5. initialize the Slots.

    Example :

    constructor(management, options) {
        super(management, options); // (1)
        this.rootdir = __dirname; // (2)
        this.coreScript = this.rootdir + '/data/'; // (3)
        this.slotSymbols = ['myInputA', 'myInputB']; // (4)
        super.initSlots(); // (5)

    Note : management (see the Management Literal part) and options (see the Options Literal part) are literals.

    The methods to implement

    You have to override two methods :

    prepareJob (inputs) {
        return super.configJob(inputs);
    /* REMARK : 'pathOfCurrentDir' is the key you gave in your core script as JSON output */
    prepareResults (chunkJson) {
        return {
            [this.outKey] : chunkJson.pathOfCurrentDir 

    These examples can be simply copied-pasted as it for your usage but you have to change the "pathOfCurrentDir". You must replace it by the key used in the stdout JSON of your core script (see the example in The core script part).

    Test your task

    In a directory named ./test/ (see the Directory tree section), you have to create a JavaScript file to test your task :

    import customTask = require('../index')
    let aTaskInstance = new customTask.my_custom_task(myManagement, myOptions);

    Management Literal

    The management literal can contain 2 keys :

    • jobManager (required module = "ms-jobmanager/build/nativeJS/job-manager-client") : an instance of a JM client (see the Job Manager section) [mandatory].
    • jobProfile (string) : the profile to run the job [optional]. This profile will be passed to the JM and will define the running settings for the job (nodes, queues, users, groups, etc.).

    Example :

    let myManagement = {
        'jobManager' : JMobject,
        'jobProfile' : 'default'

    Options Literal

    The options literal can contain 3 keys :

    • logLevel (string) : specify a verbose level [optional]. Choose between debug, info, success, warning, error and critical.
    • modules ([string]) : an array of modules to load before the run of the core script [optional].
    • exportVar (literal) : a dictionary of the variable to export before the run of the core script [optional]. Each key is the name of the variable and each value is its content.

    Example :

    let myOptions = {
        'logLevel': 'debug',
        'modules' : ['myModule1', 'myModule2'],
        'exportVar' : { 'myVar1' : '/an/awesome/path/to/a/file.exe',
         'myVar_module2' : ' -ncpu 16 -file /path/toto.txt ' }

    Push an input

    Still in your test file, create a Readable Stream with your input (in JSON format), an pipe it on the task instance :

    let aFirstInput = 'hello world';
    let rs = new stream.Readable();
    rs.push('{ "' + myInputA + '" : "' + aFirstInput + '" }'); // JSON format

    Warning : the key in the JSON must be the name of the Slot you push your data on.

    Task events

    Your task can emit events since it is a Readable Stream. When you listen these following events, the callback give you some arguments :

    • "processed" : when the task is successfully finished ; [arguments] : the results in JSON format.
    • "err" : when an error occured with the task or the JM ; [arguments] : the error.
    • "stderrContent" : when an error occured with the coreScript ; [arguments] : the error.
    • "lostJob" : when the JM has lost the job ; [arguments] : the message and the job id.

    As example :

    aTaskInstance.on('processed', res => {
        console.log("I have my results :");


    Job Manager

    A Job Manager (JM) is a MicroService necessary to run a Task. In our case, we use the ms-jobmanager package (GitHub repo), adapted for SLURM, SGE and your proper machine.


    The simpletask has been implemented only for the tests. It contains only one slot (input) :

    1. simpletask.input takes a JSON containing an "input" key (via a pipe, like x.pipe(simpleTask)).
    2. the simpletask reverses the text of the value corresponding to the "input" key.
    3. the simpletask creates a new JSON with a "reverse" key, the value being the reversed text.
    4. the simpletask pushes this new JSON on its Readable interface. Then we can use a pipe on it, like simpleTask.pipe(y).


    The dualtask has been implemented only to test the task with two slots (input1 and input2) :

    1. dualtask.input1 takes a JSON containing an "input1" key (via a pipe, like x.pipe(dualtask.input1)). Same for "input2" (y.pipe(dualtask.input2)).
    2. the dualtask concatenates the content of input1 with the content of input2.
    3. the dualtask creates a new JSON with a "concatenated" key, the value being the concatenated text.
    4. the dualtask pushes this new JSON on the Readable interface of the dualtask. Then we can use a pipe on it, like dualtask.pipe(z.slot).




    npm i taskobject

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