elency-config

elency-config-node-client

This is a node client for the elency-config-server.

Table of contents

• Prerequisites
• Install
• Use
  • Initialising the client
  • Initialisation/Retrieved
  • Refresh Failure
• License

---

Prerequisites

elency-config-node-client is built with nodejs and has the following dependencies.

• nodejs, the minimum supported LTS version is 8.9.0.

---

Install

npm install `elency-config` --save

or

1. Download elency-config-node-client.

2. Extract the above tar.gz file into a desired location on your machine.

tar xzf ./elency-config-node-client-0.0.11-beta.tar.gz

---

Initialising the client

Firstly the client needs initialising. It is advised that this would be done as part of your application startup. If the required configuration could not be retrieved it may be appropriate to kill your application and log a relevant error message.

It is also advised that any keys or secure data is not stored in your code base and is retrieved and provided to your application following best practises.

When creating a client it is advised that the HMACAuthorizationKey and configEncryptionKey would need to be read from environment variables injected into your application and not hard coded in your code bases.

To create a client execute the following:

const elencyConfig = require('elency-config');

const appId = 'awesome-app';
const environment = 'prod';
const HMACAuthorizationKey = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';
const configEncryptionKey = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';

const elencyConfigInstance = elencyConfig({
    uri: 'https://192.155.1.22:3000',
    appId,
    appVersion: '2.0.0',
    environment,
    refreshInterval: 10000,
    HMACAuthorizationKey,
    configEncryptionKey,
    retrieved: () => {},
    refreshFailure: () => {}
  });

The options provided to the client are below.

options

• uri: Defines the elency-config-server url.
• appId: Defines the application id.
• appVersion Defines the application version.
• environment Defines the environment.
• refreshInterval Defines in milliseconds whether the configuration should be refreshed on a timered basis. If the value is 0 the configuration will not be refreshed.
• HMACAuthorizationKey A 32 character (base64 encoded) string used for authorization tokens. This should match the server HMACAuthorizationKey.
• configEncryptionKey A 32 character (base64 encoded) string used to decrypt secure configuration variables. This is the value of the key associated with an application environment.
• retrieved Defines a function fired when the configuration is retrieved.
• refreshFailure Defines a function fired when a configuration refresh fails.
• localConfiguration Defines a local configuration environment. In development environments you may not want to communicate with a real elency-config-server.
• configurationMapping An optional array that defines mapping for typed configuration.

An example using localConfiguration is below:

elencyConfigInstance.localConfiguration = {
    appVersion: "1.1.2",
    environment: "production",
    configurationId: '9b386d19-fa7a-40ba-b794-f961e56ffe08',
    configurationData: {
        LOG_LEVEL: 'INFO'
    }
};

Once the client instance has been created with valid options. You can call the init function which will attempt to communicate with the elency-config-server and pull down a configuration.

try {
  await elencyConfigInstance.init();
}
catch (err) {
  console.log('An error occurred while initialising elencyConfig client', err));
  process.exit(1);
}

An example of using configurationMapping for typed configuration is below:

const elencyConfig = require('elency-config');

const appId = 'awesome-app';
const environment = 'prod';
const HMACAuthorizationKey = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';
const configEncryptionKey = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';

const elencyConfigInstance = elencyConfig({
    uri: 'https://192.155.1.22:3000',
    appId,
    appVersion: '2.0.0',
    environment,
    refreshInterval: 10000,
    HMACAuthorizationKey,
    configEncryptionKey,
    retrieved: () => {},
    refreshFailure: () => {},
    configurationMapping: [
      { configurationPropertyName: 'KeyOne', propertyName: 'KeyOneRenamed' },
      { configurationPropertyName: 'Bool', type: 'Boolean' },
      { configurationPropertyName: 'Date', type: 'Date' },
      { configurationPropertyName: 'Int', propertyName: 'int', type: 'Int' },
      { configurationPropertyName: 'Float', type: 'Float' },
      { configurationPropertyName: 'Object', type: 'Object' },
      { configurationPropertyName: 'NonExistant', type: 'int' },
      { configurationPropertyName: 'NonExistantWithFallback', type: 'int', fallback: 4 }
    ]
  });

Objects within the configurationMapping array can have the following properties

• configurationPropertyName: (required) Defines the name of the property found in the configuration.
• propertyName: (optional) Defines the target property name on the typed configuration object.
• type: (optional) Defines the target type of the property on typed configuration object. (Boolean, Date, Int, Float, Object)
• fallback: (optional) Defines a fallback value to use if one was not defined in the configuration or the property did not exist.

---

Initialisation/Retrieved

When configuration has been successfully retrieved, and assuming you have defined a retrieved function when initialising the client and retrieving configuration, the client will await the execution of the retrieved function.

In your retrieve function you may want to perform asynchonous setup tasks etc.

Once your retrieve function has been called the client will have the following functions and propertiesavailable:

functions and properties

• dispose: A function that stops refreshing if enabled.
• appVersion: A property that returns the version of the retrieved configuration.
• environment: A property that returns the environment of the retrieved configuration.
• configurationId: A property that returns the configurationId of the retrieved configuration.
• get: A function that accepts a key argument and returns the value of the key or undefined if the key cannot be found.
• getAllKeys: A function that returns all of the keys within the configuration.
• refresh: A function that can be called to refresh the configuration.
• getBoolean: (key string, fallback ) gets the value of a key as a boolean and falls back to fallback value if provided.
• getDate: (key string, fallback ) gets the value of a key as a date and falls back to fallback value if provided.
• getInt: (key string, fallback ) gets the value of a key as a int and falls back to fallback value if provided.
• getFloat: (key string, fallback ) gets the value of a key as a float and falls back to fallback value if provided.
• getObject: (key string, fallback ) gets the value of a key as an object and falls back to fallback value if provided.
• typedConfiguration: A function that can be called to returned typed configuration if configurationMapping is defined as options when creating the client.

---

Refresh Failure

If you have a refreshInterval and a refreshFailure function configured. When a refresh failure occurs the refreshFailure function will be called with an err argument.

---

License

(The MIT License)

Copyright (c) 2020 Lee Crowe a.k.a. croweman

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.