Configuration File

Configuration files are javascript/json modules. They can be used to create different sets of modules from the same codebase and to extend the server with middlewares or lifecycle methods.

Use via CLI:

themis -c hello-bye.config.js

Allowed Configuration Keys

  • modules
  • middleware
  • context
  • onStartup
  • onShutdown

Modules

Modules specified in a configuration file will be resolved relative to CWD, which usually is your project root. If you specify only a module name, not a path, Themis will try to resolve an NPM module (node_modules).

The modules specified in the configuration file can also be combined with additional modules specified as CLI options.

Example configuration (hello-bye.config.js):

module.exports = {
  modules: [
    './hello',
    './bye'
  ]
}

Middleware

Middlewares are simple express middlewares and can be added before or after Apollo Server. Most use cases can be covered by adding a middleware before. After can be used to add custom error handling for express.

The middleware configuration key is an Object which can specify before and after as lists of middlewares.

Example configuration:

module.exports = {
  middleware: {
    before: [myFirstMiddleware],
    after: [mySecondMiddleware]
  }
}

You can also mount middlewares at a specific path, by providing a middleware as an array, which will be spreaded into express.

module.exports = {
  middleware: {
    before: [
      ['/custom/path', mountSomething]
    ]
  }
}

Context

The context can be either a function or an array of functions, which will be called in a request/response query cycle. The function may return an object to be merged with the remaining context. Context functions will be called in the order the modules are loaded. Context functions from the configuration file are called before all others. If different context functions try to expose the same key on the context, they may override each other.

A context function gets an object with the req and res of the query. When using Subscriptions, the object will contain the connection key.

Example configuration:

module.exports = {
  context: () => ({
    myKey: 'myValue'
  })
}

Lifecycle Hooks

Lifecycle hooks allow to execute something onStartup, just before the server will be mounted at the given port and onShutdown, after a kill signal has been received (SIGTERM|SIGNINT).

Example configuration:

module.exports = {
  onStartup: () => doSetupWork(),
  onShutdown: () => doTeardownWork()
}
← CLIENV →