onion-config: layer-based config/data manager

Provides object storage with layers overlapping and dynamic update support.

Usage

npm install --save onion-config

const Onion = require('onion-config');

const onion = new Onion();
// ENV contains value like some_foo = '{bar: 12345}'
await onion.addLayer(new Onion.LAYERS.Env({ prefix: 'some_', json: true, }));
onion.get('foo.bar'); // => '12345'

await onion.addLayer(new Onion.LAYERS.SimpleObject({
  data: {
    foo: {
        bar: 'baz'
      },
  },
}));
onion.get('foo.bar') // => 'baz'

Idea of layers

Every next added layer merges over previous just in moment of build, on first access (.get()) or
on explicit build call (.compile, .recompile()).

Value .get() method uses path notation like some.thing.here to access inner parts of stored data. After building
.get() works just with merged .data object until next .recompile() call.

Links

To reuse big parts of your configs, you can use links. Just add value with path to other key, prefixed with @:

const onion = new Onion({ links: true });
await onion.addLayer(new Onion.LAYERS.SimpleObject({
  data: {
    resources: {
      databases: {
        MySQL: {
          host: 'localhost',
        },
      },
    },
    services: {
      login: '@resources.databases.MySQL',
    },
  }
}));
onion.get('services.login') // => { 'host': 'localhost' }

Supported config sources (Layers)

Simple object

In-code storage, not recommended. Just keeps data from given data option.

await onion.addLayer(new Onion.LAYERS.SimpleObject({
  data: {
    foo: {
      bar: 12345
    },
  },
}));
onion.get('foo.bar') // => 12345

Env parser

It parses environment variables, filtering it by prefix and supports JSON-serialized values if json option is true.
In addition, possible to change parsing with parsingSeparator option.

Warning: prefix option is just a filter for keys while parsing and it will not appear in the parsing results!

await onion.addLayer(new Onion.LAYERS.Env({ prefix: 'some_', json: true, }));

Hashicorp Vault KV2 storage

HashiCorp Vault layer, now just with kv2 engine support.
Loads all keys in basePath and stores it. Useful for micro services. Keys version support in process.
If renewInterval set above 0, then layer will renew token TTL above minTtl value periodically (every renewInterval
seconds)

await onion.addLayer(new Onion.LAYERS.Vault({
  url: env.VAULT_URL,
  token: env.VAULT_TOKEN,
  basePath,
  renewInterval: 0,
  minTtl: 7200,
}));

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