Exported utilities

QTopology exports several utility classes that are used internally, but can be used entirely on their own.

logger

Utility class and interface for logging output of the library.

cmdline

parseCommandLine function

Parses input array of strings (e.g. argv) and returns an object with colected values.

let data = ["--a", "1", "-b", "2", "some_value1", "some_value2", "-c"];
let res = qtopology.parseCommandLine(data);

The result is the following:

{
    a: "1",
    b: "2",
    c: true,
    _: ["some_value1", "some_value2"]
}

parseCommandLineEx function

The same as parseCommandLine with additional parameter that describes mapping:

let data = ["--a", "1", "-b", "2", "some_value1", "some_value2", "-c"];
let res = qtopology.parseCommandLineEx(data, { a: "action", c: "config" });

The result is the following:

{
    a: "1",
    action: "1",
    b: "2",
    c: true,
    config: true,
    _: ["some_value1", "some_value2"]
}

This way you can add shortcut names for longer names (e.g. -a for --append).

CmdLineParser object

Utility class for parsing command-line parameters.

let qtopology = require("qtopology");
let cmdl = new qtopology.CmdLineParser();
cmdl.define("n", "name", "default_name", "This parameter sets the name");
let res = cmdl.process(some_string_arry);

This code processes input array of string (most often this would be process.argv) and it would output an object with property name.

For instance, if command line would be any of the following:

node main.js -n my_name
node main.js --name my_name

The result would be

{
    name: "my_name"
}

pattern matcher

Simple pattern-matching class, used for instance in filtering and routing:

let data = { a: 4, b: "8ba" };
let data2 = { a: 4, b: "8b" };
let filter = { b: { $like: "$[0-5]b" } };
let target = new pm.PaternMatcher(filter);
target.isMatch(data); // returns false
target.isMatch(data2); // returns true

child process restarter

This class provides automatic restarting of given child process (similar to forever module). See demo for an example.

It comes in two flavors, one calls spawn and the other calls fork. The former one can call any executable and the latter one just need path to the javascript file.

Spawn

This one can call any executable:

const qtopology = require("qtopology");
let obj = new qtopology.ChildProcRestarterFork("child.js", []);
obj.start();

Fork

This one just executes given javascript file, no need to specify node as execution application:

const qtopology = require("qtopology");
let obj = new qtopology.ChildProcRestarterSpawn("node", ["child.js"]);
obj.start();

General

This class exposes the most options and is called by the other two:

const qtopology = require("qtopology");
let obj = new qtopology.ChildProcRestarter({
    cmd : "node",
    args: ["child.js"],
    args_restart: ["child.js", "-a"],
    use_fork: false,
    stop_score: 5
});
obj.start();

Parameter args_restart is optional and, when present, is used upon process restart. In that scenarion, the argument args is used only the first time.

If parameter args_restart is not provided, the argument args is used each time.

Minimal HTTP server

This utility class represents minimal HTTP server that serves simple REST requests as well as GET requests for static content. There is no:

CRON-like expression parser

This utility object support a subset of CRON expressions

*    *    *    *    *    *
┬    ┬    ┬    ┬    ┬    ┬
│    │    │    │    │    |
│    │    │    │    │    └ day of week (0 - 6) (also supports )
│    │    │    │    └───── month (1 - 12)
│    │    │    └────────── day of month (1 - 31)
│    │    └─────────────── hour (0 - 23)
│    └──────────────────── minute (0 - 59)
└───────────────────────── second (0 - 59)

Each spot can contain one of the following:

Examples

Usage

// import library
const parser = require('qtopology').CronTabParser;

// create instance
let target = new parser('* * * * * 4'); // allow only Thursdays

// query instance
console.log(target.isIncluded(new Date(2018, 0, 31, 6, 45, 13))); // false
console.log(target.isIncluded(new Date(2018, 1, 1, 6, 45, 12)));  // true
console.log(target.isIncluded(new Date(2018, 1, 2, 6, 45, 11)));  // false

stripJsonComments function

This utility function takes string containing JSON with non-standard comments and removes the comments. Very useful for processing the configuration files.

Supports both single-line (//) and start-end (/* and */) comments.

If your input string looks like this:

{
    // This is a comment
    "a": 12,
    /* This is another comment */
    "b": 45
}

Send this string through the utility function:

let qtopology = require("qtopology");
let output = qtopology.stripJsonComments(input_string);

The output will look like this:

{
    "a": 12,
    "b": 45
}

readJsonFileSync function

Utility function that: