NodeJS Tutorial

NodeJS Tutorial

1601583660

TypeScript Native Prometheus Client for Deno

promts

promts is a native TypeScript based implementation of promclient. Create Prometheus compatible metrics for your TypeScript/Deno Service.

Pronounced: Prom-tsss

Background

Since no current TypeScript Native implementation for Node.JS or Deno seemed to exist, promts fills the gap. This allows for your TypeScript code to have type checking on the promclient types.

Install

Usage from Deno

    import { MetricsManager } from 'https://deno.land/x/promts@v0.1.4

Usage

Counters

Counters are monotonically increasing–counters never go down. Think http request.

    import { MetricsManager } from 'https://deno.land/x/promts@v0.1.4
    const httpTotalRequests = MetricsManager.getCounter("http_requests_total")
      .with({ service: "web" });
    httpTotalRequests.inc();

Gauges

Gauges can go up and down… Think water levels, temperature, thread counts.

    import { MetricsManager } from 'https://deno.land/x/promts@v0.1.4
    const processCount = MetricsManager.getGauge("process_count").with({app:"server"});
    processCount.inc(); // 1
    processCount.inc(3);
    processCount.dec();
    processCount.getTotal(); // 3

Histogram

Histograms can be though of as a list of counters. These counters each represent a bucket. Buckets have a label le which denotes the upper bound. Histograms also contain their sum and count.

    import { Histogram } from 'https://deno.land/x/promts@v0.1.4
    const histogram = new Histogram("http_request_duration");
    histogram.observe(0.01);
    histogram.observe(0.1);
    histogram.observe(5);
    histogram.observe(5);
    histogram.getCount(); // 4
    histogram.getSum();   // 10.11
    histogram.toString(); // dump to string

Pushgateway

    const pushgateway = new PushGateway("test_job");
    pushgateway.sendOnInterval(MetricsManager);

Dumping the metrics in prometheus format

    import { MetricsManager } from 'https://deno.land/x/promts@v0.1.4
    const metricsData = MetricsManager.toString();

Contribute

Please refer to CONTRIBUTIONS.md for information about how to get involved. We welcome issues, questions, and pull requests.

Maintainers

License

  • This project is licensed under the terms of the MIT open source license. Please refer to LICENSE for the full terms.

Future Roadmap

  • Add support for configurable histogram buckets.
  • Add the summary metric type.

Download Details:

Author: base698

Source Code: https://github.com/base698/promts

#deno #nodejs #node #javascript

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TypeScript Native Prometheus Client for Deno
Autumn Blick

Autumn Blick

1598839687

How native is React Native? | React Native vs Native App Development

If you are undertaking a mobile app development for your start-up or enterprise, you are likely wondering whether to use React Native. As a popular development framework, React Native helps you to develop near-native mobile apps. However, you are probably also wondering how close you can get to a native app by using React Native. How native is React Native?

In the article, we discuss the similarities between native mobile development and development using React Native. We also touch upon where they differ and how to bridge the gaps. Read on.

A brief introduction to React Native

Let’s briefly set the context first. We will briefly touch upon what React Native is and how it differs from earlier hybrid frameworks.

React Native is a popular JavaScript framework that Facebook has created. You can use this open-source framework to code natively rendering Android and iOS mobile apps. You can use it to develop web apps too.

Facebook has developed React Native based on React, its JavaScript library. The first release of React Native came in March 2015. At the time of writing this article, the latest stable release of React Native is 0.62.0, and it was released in March 2020.

Although relatively new, React Native has acquired a high degree of popularity. The “Stack Overflow Developer Survey 2019” report identifies it as the 8th most loved framework. Facebook, Walmart, and Bloomberg are some of the top companies that use React Native.

The popularity of React Native comes from its advantages. Some of its advantages are as follows:

  • Performance: It delivers optimal performance.
  • Cross-platform development: You can develop both Android and iOS apps with it. The reuse of code expedites development and reduces costs.
  • UI design: React Native enables you to design simple and responsive UI for your mobile app.
  • 3rd party plugins: This framework supports 3rd party plugins.
  • Developer community: A vibrant community of developers support React Native.

Why React Native is fundamentally different from earlier hybrid frameworks

Are you wondering whether React Native is just another of those hybrid frameworks like Ionic or Cordova? It’s not! React Native is fundamentally different from these earlier hybrid frameworks.

React Native is very close to native. Consider the following aspects as described on the React Native website:

  • Access to many native platforms features: The primitives of React Native render to native platform UI. This means that your React Native app will use many native platform APIs as native apps would do.
  • Near-native user experience: React Native provides several native components, and these are platform agnostic.
  • The ease of accessing native APIs: React Native uses a declarative UI paradigm. This enables React Native to interact easily with native platform APIs since React Native wraps existing native code.

Due to these factors, React Native offers many more advantages compared to those earlier hybrid frameworks. We now review them.

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TypeScript — Compilation & the TypeScript Compiler

TypeScript provides a command-line utility tsc that compiles (transpiles) TypeScript files (_.ts_) into JavaScript. However, the tsc compiler (short for TypeScript compiler) needs a JSON configuration file to look for TypeScript files in the project and generate valid output files at a correct location.

When you run tsc command in a directory, TypeScript compiler looks for the tsconfig.json file in the current directory and if it doesn’t find one, then it keeps looking up the directory tree until it finds one. The directory where the tsconfig.json is located is considered as the root of the project.

You can manually provide a path to the tsconfig.json file using --project or -p command-line flag. This file doesn’t need to have the tsconfig.json filename if you are using this flag with the exact file path. However, you can also provide the directory path that contains the tsconfig.json file.

$ tsc -p /proj/x/tsconfig.dev.json

If the TypeScript compiler fails to locate this configuration file, you would get an error. But you can provide settings enlisted in this file through the equivalent command-line options which we will cover in the next lesson.

Structure of tsconfig.json

So what does this file contain and what exactly it controls?

{
  "files": [
    "src/lib/person.ts",
    "src/lib/student.ts",
    "src/main.ts"
  ],
  "compilerOptions": {
    "target": "ES6",
    "module": "CommonJS",
    "outDir": "./dist/development"
  }
}

The tsconfig.json file is a standard JSON file, however, it supports JSON5 specifications, so you can use comments, single quotes, and more. It contains some root-level options and some compiler options. The root-level options are options that are outside of the compilerOptions object, so in the above example, files is a root-level option.

The root-level options control how the project is presented to the TypeScript compiler, such as which TypeScript files to consider for the compilation. The compiler options contain settings for the TypeScript compiler such as where to output the compiled JavaScript files in the project directory.

ROOT-LEVEL OPTIONS

These options control how the project is presented to the TypeScript compiler for the compilation and static type analysis. These options must be kept outside compilerOptions object of the tsconfig.json file.

● files

The files array contains the location of the TypeScript files to consider for the compilation. These can be either relative paths or absolute paths on the disk. A relative path is located relative to the location of the tsconfig.json file (AKA root of the project).

/projects/sample/
├── a.ts
├── src/
|  ├── b.ts
|  ├── c.ts
|  ├── ignore.ts
|  └── lib/
|     ├── d.ts
|     └── e.ts
└── tsconfig.json

Let’s consider that we have the above directory structure in our project. As you can see, the TypeScript files (.ts) are located in multiple directories. We want to compile all the .ts files except the ignore.ts file. Hence we would provide relative paths of these files in the files options of tsconfig.json.

// tsconfig.json

{
    "files": [
        "a.ts",
        "src/b.ts",
        "./src/c.ts",
        "src/lib/d.ts",
        "./src/lib/e.ts"
    ]
}

You can also provide absolute paths of these files but relative paths are most recommended since they would be consistent on all the systems. All the relative paths are resolved against the path of tsconfig.json file in the project. You can optionally provide ./ or ../ prefix to locate the file.

Since we haven’t provided any compilerOptions values, all the default values for the compiler options are used which we will talk about in a bit. The TypeScript compiler compiles these files and outputs the JavaScript with .js extension by keeping the same file name as the individual input file.

The TypeScript compiler also preserves the original file path, hence the .js output file will be generated where the input file was in the directory structure. When you run the tsc command from the directory where your tsconfig.json file is located, you are going to see the result below.

/projects/sample/
├── a.js
├── a.ts
├── src/
|  ├── b.js
|  ├── b.ts
|  ├── c.js
|  ├── c.ts
|  ├── ignore.ts
|  └── lib/
|     ├── d.js
|     ├── d.ts
|     ├── e.js
|     └── e.ts
└── tsconfig.json

As you can see, the TypeScript compiler compiled all the input TypeScript files listed inside files array of tsconfig.json. You can’t see the ignore.js file since ignore.ts file was not included in the files array.

The directory where the tsconfig.json file is located is considered as the root of the project, AKA the root directory. You can also include a file from outside this root directory, such by including "../x.ts" in the files array where x would be in the parent directory of the root directory. Since the TypeScript compiler preserves the input file path, it will generate x.js in the parent directory of the root directory.

● include & exclude

The files option is great when you have relatively few files to work with. But when your project is big and contains hundreds of source files located in a nested directory structure, then handpicking file paths is not practical.

To solve this issue, we can use include option. This option is just like files, however, we can optionally provide glob patterns to locate input files. The exclude options behave the same, except it removes the files from the compilation that may have been included by the include option.

// tsconfig.json

{
    "include": [
        "a.ts",
        "src/**/*.ts"
    ],
    "exclude": [
        "./**/*/ignore.ts"
    ]
}

In the above tsconfig.json, we have removed the files option and added include which adds a.ts file from the root directory and all the .ts file from the src directory. Since this would also include any ignore.ts from the src directory, we have provided the exclude option that excludes any ignore.ts file from the compilation if located inside the src directory.

When we run the tsc command now, results won’t be any different since the files considered for the compilation both in the previous example and this example are the same.

/projects/sample/
├── a.js
├── a.ts
├── src/
|  ├── b.js
|  ├── b.ts
|  ├── c.js
|  ├── c.ts
|  ├── ignore.ts
|  └── lib/
|     ├── d.js
|     ├── d.ts
|     ├── e.js
|     └── e.ts
└── tsconfig.json

The TypeScript compiler automatically excludes files from the "node_modules", "bower_components", "jspm_packages" and "<outDir>" directories, where <outDir> is the value of outDir compiler-option provided by you. This prevents any .ts file from these directories getting included in the compilation process by accident.

#nodejs #typescript #deno #programming #javascript #deno

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