node-microsvc-lib


Installation

``bash
npm install node-microsvc-lib --save
`

Usage

Creating a microservice app:

app.ts
`javascript
"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:
1. params.js file - ServiceParams instance gets loaded along with the default values;
2. params.ENV_NAME.js file - the one that overrides values in ServiceParams per env;
3. IConfigsProvider - if a correspondent key name exists the value from the provider overrides the current one (after app/microservice init);
4. 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).

$3

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

$3

See the ref implementaion

config/config.ts
`javascript
"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
`javascript
"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)
`javascript
"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
`bash
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:
`bash
nvm install -s
``