alexxnica / arsenal

Common utilities for the open-source Scality S3 project components

Arsenal

Common utilities for the S3 project components

Within this repository, you will be able to find the shared libraries for the multiple components making up the whole Project.

• Guidelines
• Shuffle to shuffle an array.
• Errors load an object of errors instances.
  • errors/arsenalErrors.json

Guidelines

Please read our coding and workflow guidelines at scality/Guidelines.

Contributing

In order to contribute, please follow the Contributing Guidelines.

Shuffle

Usage

import { shuffle } from 'arsenal';

let array = [1, 2, 3, 4, 5];

shuffle(array);

console.log(array);

//[5, 3, 1, 2, 4]

Errors

Usage

import { errors } from 'arsenal';

console.log(errors.AccessDenied);

//{ [Error: AccessDenied]
//    code: 403,
//    description: 'Access Denied',
//    AccessDenied: true }

Clustering

The clustering class can be used to set up a cluster of workers. The class will create at least 1 worker, will log any worker event (started, exited). The class also provides a watchdog which restarts the workers in case of failure until the stop() method is called.

Usage

Simple

import { Clustering } from 'arsenal';

const cluster = new Clustering(clusterSize, logger);
cluster.start(current => {
    // Put here the logic of every worker.
    // 'current' is the Clustering instance, worker id is accessible by
    // current.getIndex()
});

The callback will be called every time a worker is started/restarted.

Handle exit

import { Clustering } from 'arsenal';

const cluster = new Clustering(clusterSize, logger);
cluster.start(current => {
    // Put here the logic of every worker.
    // 'current' is the Clustering instance, worker id is accessible by
    // current.getIndex()
}).onExit(current => {
    if (current.isMaster()) {
        // Master process exiting
    } else {
        const id = current.getIndex();
        // Worker (id) exiting
    }
});

You can handle exit event on both master and workers by calling the 'onExit' method and setting the callback. This allows release of resources or save state before exiting the process.

Silencing a signal

import { Clustering } from 'arsenal';

const cluster = new Clustering(clusterSize, logger);
cluster.start(current => {
    // Put here the logic of every worker.
    // 'current' is the Clustering instance, worker id is accessible by
    // current.getIndex()
}).onExit((current, signal) => {
    if (signal !== 'SIGTERM') {
        process.exit(current.getStatus());
    }
});

You can silence stop signals, by simply not exiting on the exit callback

Shutdown timeout

import { Clustering } from 'arsenal';

const cluster = new Clustering(clusterSize, logger, 1000);
cluster.start(current => {
    // Put here the logic of every worker.
    // 'current' is the Clustering instance, worker id is accessible by
    // current.getIndex()
}).onExit((current, signal) => {
    if (signal === 'SIGTERM') {
        // releasing resources
    }
});

By default, the shutdown timeout is set to 5000 milliseconds. This timeout is used only when you explicitly call the stop() method. This window is used to let the application release its resources, but if timeout occurs before the application has finished it's cleanup, a 'SIGKILL' signal is send to the process (which results in an immediate termination, and this signal can't be caught).