Legman-Logstash

Legman-Logstash is a writeable stream build for sending messages from a Legman stream into a Logstash instance.

How to use in NodeJS

At first you have to install this module and Legman into your application:

npm i --save legman legman-logstash
# OR
yarn add legman legman-logstash

After that you can import and use LegmanLogstash in your code.

Using Legman with Logstash in TypeScript

import Legman from "legman";
import LegmanLogstash from "legman-logstash";

const logstashPort: number = 9500;
const logstashHostname: string | undefined = "logstash";
const logstash = new LegmanLogstash(logstashPort, logstashHostname);

const loggerLeg = new Legman({app: "Identifier for my application"});
loggerLeg
    .filter((message) => ["error", "warn", "info"].includes(message.loglevel)) // pre-filter messages for Logstash
    .pipe(logstash);
const httpLogger = loggerLeg.influx({context: "http"}, true);

app.get("/example", (req, res, next) => {
    httpLogger.write({
        msg: "Incoming request",
        loglevel: "info",
        path: req.url,
        method: req.method,
    });
    // ...
});

Using Legman with Logstash in JavaScript

const Legman = require("legman");
const LegmanLogstash = require("legman-logstash");

const logstashPort = 9500;
const logstashHostname = "logstash";
const logstash = new LegmanLogstash(logstashPort, logstashHostname);

const loggerLeg = new Legman({app: "Identifier for my application"});
loggerLeg
    .filter((message) => ["error", "warn", "info"].includes(message.loglevel)) // pre-filter messages for Logstash
    .pipe(logstash);
const httpLogger = loggerLeg.influx({context: "http"}, true);

app.get("/example", (req, res, next) => {
    httpLogger.write({
        msg: "Incoming request",
        loglevel: "info",
        path: req.url,
        method: req.method,
    });
    // ...
});

How to configure Logstash

Logstash should use the tcp input with json_lines codec. Take a look at the example and the docker-compose.yml.

Example configuration:

input { tcp { port => 9500 codec => json_lines } } output { elasticsearch { index => "example" hosts => ["elasticsearch:9200"] } }

Example

You can run a full integrated example with the ELK complete stack by running npm run docker:example. After that you can open Kibana with your browser on its default port 5601 on your docker host.

On your first visit you have to create an index for Elasticsearch with the help of Kibana. Click on Management and take the link to Index Patterns on the Kibana tab. Input example as index pattern and click next step. Select a timestamp from the dropdown menu. @timestamp is the one from Logstash and timestamp is the one from your application. I would recommend the timestamp property, because it is the timestamp when the message was emitted and not the timestamp when the message was received by Logstash.

The example will log random messages from NodeJS to Logstash to ElasticSearch to Kibana. The source code of the example is located at the ./example folder.

Script tasks

transpile: Transpiles the library from TypeScript into JavaScript with type declarations
lint: Lints your code against the recommend TSLint ruleset.
test: Transpiles, lints and runs software-tests with coverage.
leakage: Transpiles, lints and runs software-tests with leakage tests.
docker:lint: Runs the lint task in a docker environment.
docker:test: Runs the test task in a docker environment.
docker:leakage: Runs the leakage task in a docker environment.
docker:example: Runs an example within the docker environment.

atd-schubert/legman-logstash