node-microsvc-lib

node-microsvc-lib

Installation

npm install node-microsvc-lib --save

Usage

Creating a microservice app:

app.ts

"use strict";

import {Microservice, ConsoleLogger} from "node-microsvc-lib";

// factories/modules
import {RequestLogger} from "./factories/request_logger";
import {HealthCheck} from "./factories/health_check";
import {TestRestCtrl} from "./factories/rest_service";

// configs
import configs = require("./config/config");

const logger = new ConsoleLogger();

// create microservice appv
const app = new Microservice(configs, logger);

app.register_dependency("logger", logger);

app.register_factory("request_logger", RequestLogger);
app.register_factory("test_rest_ctrl", TestRestCtrl);
app.register_factory("health_check", HealthCheck);

process.on("uncaughtException", (err:Error)=>{
  logger.fatal(err);
});

app.init().catch((err) => {
   return logger.error(err);
}).then(()=> {
   logger.info("APP STARTED");
});

How configuration works

The Microservice instance expects a ServiceConfigs instance. This ServiceConfigs instance requires the base dir __dirname, an instance of AppBaseConfigs and an (optional) instance of IConfigsProvider.

Three sets of configuration values exist:

• Parameters - values can be of type STRING, BOOL, INT_NUMBER or FLOAT_NUMBER;
• Feature Flags - values are always of boolean type;
• Secrets - values are always of string type.

ServiceConfigs (Required for Microservice obj instantiation)

This is the object that the Microservice requires to source all its runtime configurations.

IConfigsProvider (Optional)

Optional instance that fetches all config values from an external service such as consul or hashicorp vault.

Load order / precedence

The order of loading:

• params.js file - ServiceParams instance gets loaded along with the default values;
• params.ENV_NAME.js file - the one that overrides values in ServiceParams per env;
• IConfigsProvider - if a correspondent key name exists the value from the provider overrides the current one (after app/microservice init);
• Environment vars - all parameters can be overridden by passing an uppercase env var with the param key name (after app/microservice init)

In summary, env vars always win (if defined).

Minimum config structure

src/config/config.ts (main config object) 
src/config/param.ts (default params definition)

Example of config code structure

See the ref implementaion

config/config.ts

"use strict";

import {ServiceConfigs, AppBaseConfigs} from "node-microsvc-lib";

let app_base_confs = new AppBaseConfigs();
app_base_confs.env = process.env.APP_ENV || 'dev_local';
app_base_confs.solution_name = "my_solution";
app_base_confs.app_name = "my_app";
app_base_confs.app_version = "0.0.1";
app_base_confs.app_api_prefix = "";
app_base_confs.app_api_version = "1";

export = new ServiceConfigs(__dirname, app_base_confs, null);

config/params.ts

"use strict";

import {ParamTypes, ServiceParams} from "node-microsvc-lib";
let params = new ServiceParams();

params.add_param(
	"test_param",
	ParamTypes.STRING, 
	"default_val",
	"test param to be overridden by env_var"
);
 
params.add_feature_flag(
	"RUN_EXPRESS_APP",
	true, 
	"start the express application"
);

params.add_secret(
	"secret1", 
	null, // secrets should be loaded from an IServiceProvider or a non-github-tracked per env override file 
	"db password example"
);

export = params;

config/overrides.stage.ts (optional file see step 2 above - where "stage" comes from APP_ENV)

"use strict";

import {ServiceParams} from "node-microsvc-lib";

module.exports = function(configs:ServiceConfigs){
	// override params, feature_flags or secrets values'

	configs.override_param_value("kafka_conn_string", "stage:9092");

};

Pre-requisites for contributing

NVM - Node Version Manager - https://github.com/creationix/nvm

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash

After NVM is installed, go to the proect directory and execute this to download and install the correct node version:

nvm install -s