Git Service Adapter

Description

Git Service Adapter is a configurable plug-and-play module that allows applications to leverage GitHub as a remote configuration storage container. Essentially, Git Service Adapter functions as a wrapper around the GitHub v3 API. It is intended as an intermediary tool for applications migrating towards true cloud-based remote configuration. Advantage of remote configuration are discussed elsewhere.

Table of Contents

• Security Considerations
• Installation
• Set-up
• Basic Usage
• Arguments
• Initialization
• Methods
  • ServiceAdapter.prototype.establishConnection()
    • Description
    • Arguments
    • Output
  • ServiceAdapter.prototype.fetchConfigFile()
    • Description
    • Arguments
    • Output
  • ServiceAdapter.prototype.printConnection()
    • Description
    • Arguments
    • Output
  • ServiceAdapter.prototype.togglePollLoop()
    • Description
    • Arguments
    • Output
• Events
  • configUpdated
    • Description
• Contribute
• Support

Security Considerations

The intended use of this package is through a service or "bot" user account. It is recommended that this account not be connected to any third-party applications and, of course, that only private repositories be provisioned. A Personal Access Token is required. The token must have read permissions for repositories, files, and--if you intend to access repositories stored within connected organizations--organizations. It is up to development teams to determine least-privilege principles and manage token-cycling.

Note: It is up to you to determine whether or not Git Service Adapter is an appropriate tool for your application. While utilization allows for the separation of environment configurations from your codebase (GOOD), GitHub repositories are not specifically designed with this use-case in mind. With appropriate precautions (such as--but not limited to--those described above), however, it provides a serviceable option to quickly get up-and-running with remote configurations. As a disclaimer, use at your own discretion.

Installation

Git Service Adapter can be installed using the package manager of your choosing. The example command below uses yarn.

$ yarn add git-service-adapter

Git Service Adapter ships with both CommonJS and ES6 compatibility out-of-the-box.

Set-up

While it accepts arguments for all other parameters (except NODE_ENV, which is only read internally through process.env), arguments can be omitted in favour of allowing Git Service Adapter to read its own configuration variables from process.env directly. It is up to you to balance verbosity with readability. The following variables are available:

GIT_SERVICE_ACCESS_TOKEN=<your_bot_account_access_token>
GIT_USERNAME=<your_bot_account_username>
GIT_ORG=<your_org>
GIT_REPO=<your_config_repo>
GIT_FILE=<your_remote_config_file_name>
NODE_ENV=<env>

In keeping with convention, please note that if NODE_ENV is not set to 'development', a production environment will be assumed in order to help prevent errors as well as to moderate logging behaviors securely.

Basic Usage

1. Import or require in your application:

import ServiceAdapter from 'git-service-adapter';

2. Instantiate class (please see Arguments section to see which arguments are optional and their defaults):

const adapter = new ServiceAdapter({
    token: process.env.GIT_SERVICE_ACCESS_TOKEN,
    username: process.env.GIT_USERNAME,
    fileName: process.env.GIT_FILE,
    organization: process.env.GIT_ORG,
    repository: process.env.GIT_REPO,
    pollInterval: 1000 * 60 * 5,
    mute: false,
    local: false,
    verbose: true,
    timeoutFn: setTimeout
});

3. Check connection to remote repository by calling establishConnection():

await adapter.establishConnection();

4. Extract emitter (optional: only required if a pollInterval is specified):

const emitter = adapter.emitter;

5. Setup configUpdated event listener (optional: see #4):

emitter.addListener('configUpdated', someFunction);

6. Request configs directly using fetchConfigFile() (useful for asynchronously awaiting result for first-time config load, or wherever a pollInterval is not specified):

const initialConfig = await adapter.fetchConfigFile();

Arguments

Name	Default	Description
fileName?	process.env.GIT_FILE	The name of the configuration file in the remote repository. Argument is optional, however a value is required if one cannot be read from process.env.
local?	false	Indicates whether a file should be read from the local environment. A file named local.json must be included at the root of the project directory with the required environment variables stored inside. Make sure you .gitignore this file!
organization?	process.env.GIT_ORG	The name of the organization storing the remote repository and configuration file. This argument is truly optional -- if not included, it is assumed that the configs are stored in a repository directly on the service account.
pollInterval?	undefined	An optional argument used to provide the interval at which Git Service Adapter should check the configuration repository. Argument should be provided in milliseconds. If no argument is provided, polling does not occur. If an argument is provided, polling is initiated automatically.
repository?	process.env.GIT_REPO	The name of the remote repository. Argument is optional, however a value is required if one cannot be read from process.env.
setTimeout?	setTimeout (default NodeJs timeout function)	Optional custom timeout function. Due to historic buggy behaviors of the native NodeJS timeout function, users have the option of writing or wrapping a timeout function from another language if necessary. If no pollInterval is set, poll-loop will not trigger regardless of whether or not a custom function is passed.
token?	process.env.GIT_SERVICE_ACCESS_TOKEN	The Personal Access Token of the service account. Argument is optional, however a value is required if one cannot be read from process.env.
username?	process.env.GIT_USERNAME	The name of the service account. Argument is optional, however a value is required if one cannot be read from process.env.
verbose?	false	Toggles whether or not retrieved configurations should be logged to console. This happens independently of mute. If process.env.NODE_ENV is not explicitly set to 'development', this argument will be ignored to prevent accidental secret leakage.

Initialization

Upon instantiation, ServiceAdapter performs very basic validation, ensuring that the required fields have either been passed as arguments or are readable from process.env.

In local development, missing arguments will not result in an error, however a warning message will be displayed.

If process.env.NODE_ENV is not explicitly set to 'development', missing essential arguments will result in a thrown error. This is done to prevent app start-up whenever there is an issue with environment configs.

Methods

ServiceAdapter.prototype.establishConnection()

Description

An asynchronous method used to verify a working connection with the remote configuration repository. If called, this method will establish a connection with the remote repository regardless of whether or not the local flag is set to true. In both success and failure, this method logs to console if mute is set to false.

In addition to logging to the console, method will return a Boolean value, allowing user to provide custom handling in the event that establishing a connection is unsuccessful.

Please note that this method does not open a connection in the form of a stream, but rather hits the endpoint once to ensure that the adapter is able to connect to the appropriate repository with valid credentials.

Arguments

None

Output

Boolean (true or false)

ServiceAdapter.prototype.fetchConfigFile()

Description

An asynchronous method used to manually retrieve configuration. This method must be called to kick-start automatic configuration retrieval. Can be called even when pollInterval is set. Use this method to await retrieval of initial configurations upon app startup.

This method does not allows for arguments to be passed. If for some reason multiple repositories need to be accessed (i.e. a base configuration and then environmental configurations -- not at all recommended, but a possibility: in general it is best to keep a unified set of configurations per environment), you should use multiple ServiceAdapter instances, and handle responses accordingly in your application.

If there is an error fetching the remote configuration, method will return false to allow for error custom error handling. If the mute flag is set to false, a message will be logged to console. If a pollInterval is passed, failure will not break the loop.

Arguments

None

Output

Success: Response in JavaScript Object format Failure: false

ServiceAdapter.prototype.printConnection()

Description

A method used to log connection details. The following are outputted to console: username, repository, organization, fileName. Useful for debugging, or to log connection at app initialization. Ignores both verbose and mute flags, and is agnostic of production / development environments.

Arguments

None

Output

none

ServiceAdapter.prototype.togglePollLoop()

Description

Polling behavior can be toggled on and off by passing true or false to this method. The default state is true. If for whatever reason no polling behavior is desired, this function should be called before fetchConfigFile(). Method will ignore non-boolean arguments.

If mute is set to false, this method will log to the console.

Arguments

mode: Boolean

Output

None

Events

configUpdated

Description

This event is emitted under the following conditions:

1. A configuration has been retrieved from a remote or from local local.json file.
2. Internal reconciling process finds a difference between the incoming configuration and the existing configuration in memory.

Listen to this event to respond to configuration changes within your application. See Basic Usage for an example.

Contribute

If you encounter any problems, please open an issue! If you would like to contribute features or functionality, feel free to submit a pull request. Feature requests also accepted.

The following items will receive priority:

• Unit Tests (package has been extensively tested via manual testing)

Support

• Buy me a coffee
• Read my writing