Context

Every middleware or call handler is passed an application context. A Mali Context encapsulates the Mali Request and Response objects into a single object which provides a few helpful properties and methods for inspecting and handling gRPC remote calls.

Example

async function sayHello(ctx) {
  // get some value from request metadata
  console.log(ctx.get('foo'))

  // set some response header metadata
  ctx.set('foo', 'bar')

  // get some data from call request
  const name = ctx.req.name

  // create response payload
  ctx.res = { message: `Hello ${name}!` }

  // set response status / trailer metadata
  ctx.setStatus('biz', 'baz')
}

Properties

Context specific properties. Some of these are just aliases and deleagated to the appropriate request or response properties.

ctx.name

The call name as defined within the protocol buffer definition.

console.log(ctx.name) // 'SayHello'

ctx.fullName

The full call name as defined within the protocol buffer definition, including the package and service name.

console.log(ctx.fullName) // '/helloworld.Greeter/SayHello'

ctx.service

The service name of the call.

console.log(ctx.service) // 'Greeter'

ctx.package

The package name of the call.

console.log(ctx.package) // 'helloworld'

ctx.app

The Mali application instance reference.

ctx.type

The call type. One of CallType enums. This is an alias for ctx.request.type.

console.log(ctx.type) // 'unary'

ctx.call

The internal gRPC call instance reference. This is an alias for ctx.request.call.

ctx.request

The Mali Request object.

ctx.response

The Mali Response object.

ctx.req

The request object. This is alias for ctx.request.req. In case of UNIRY and RESPONSE_STREAM calls it is simply the gRPC call's request. In case of REQUEST_STREAM and DUPLEX calls it's the gRPC call reference itself.

console.log(ctx.req) // { name: 'Bob' }

ctx.res

The response object. This is an alias to ctx.response.res. This is set only in case of DUPLEX calls, to the the gRPC call reference itself. In all other cases set the res property to the actual response message / object in case of UNIRY and REQUEST_STREAM calls, and to the output stream in case of RESPONSE_STREAM calls. When a stream it is automatically piped into the call.

ctx.res = { message: 'Hello World!' }

ctx.metadata

The call's request metadata plain object. This is an alias to ctx.request.metadata.

console.log(ctx.metadata)
// { 'user-agent': 'grpc-node/1.7.1 grpc-c/1.7.1 (osx; chttp2)' }

Functions

ctx.get()

Get request metadata value. This is an alias to ctx.request.get().

console.log(ctx.get('user-agent'))
// 'grpc-node/1.7.1 grpc-c/1.7.1 (osx; chttp2)'

ctx.set()

Set a response header metadata value. This is an alias to ctx.response.set().

ctx.set('foo', 'bar')

Or we can set using an object:

ctx.set({
  foo: 'bar'
})

ctx.sendMetadata()

Send response header metadata. Optionally provide header metadata object directly as an argument and that is set and sent. If param is not provided sendMetadata sends the existing metadata in the response. If it is provided existin metadata is cleared and is set to the object adn then sent. This is an alias to ctx.response.sendMetadata().

ctx.sendMetadata({
  foo: 'bar'
})

ctx.setStatus()

Set response status / trailer metadata value. This is an alias to ctx.response.setStatus().

ctx.setStatus('foo', 'bar')

Or using an object

ctx.setStatus({
  foo: 'bar'
})

ctx.getStatus()

Get response status / trailer metadata value. This is an alias to ctx.response.getStatus().

console.log(ctx.getStatus('foo')) // 'bar'