Ping example (AsyncAPI v3)
This example will use a ping example that you can find
here.
The code for this example have already been generated and can be
read, in the subdirectories app/ and user/. You can execute examples with
make examples, or just one with EXAMPLE=<example> make examples where the
example is <example>/<broker> (here EXAMPLE=ping/nats).
In order to recreate the code for user and application, you have to run this command:
# Install the tool
go install github.com/dimonoff/asyncapi-codegen/cmd/asyncapi-codegen@latest
# Generate the code from the asyncapi file
asyncapi-codegen -i examples/ping/v3/asyncapi.yaml -p main -o ./ping.gen.go
We can then go through the possible application and user implementations that
use ping.gen.go.
type Subscriber struct {
Controller *AppController
}
func (s Subscriber) PingRequestOperationReceived(ctx context.Context, ping PingMessage) {
// Publish the pong message, with the callback function to modify it
// Note: it will indefinitely wait to publish as context has no timeout
err := s.Controller.ReplyToPingRequestOperation(ctx, ping, func(pong *PongMessage) {
// Reply with the same event than the ping
pong.Payload.Event = ping.Payload.Event
})
// ...
}
func main() {
// ...
// Create a new application controller
ctrl, _ := NewAppController(/* Add corresponding broker controller */)
defer ctrl.Close(context.Background())
// Subscribe to all (we could also have just listened on the ping request channel)
sub := ServerSubscriber{Controller: ctrl}
if err := ctrl.SubscribeToAllChannels(context.Background(), sub); err != nil {
// -- Error management
}
defer ctrl.UnsubscribeFromAllChannels(context.Background())
// Process messages until interruption signal
// ...
}
// Create a new user controller
ctrl, err := NewUserController(/* Add corresponding broker controller */)
// -- Error management
defer ctrl.Close(context.Background())
// Make a new ping message
req := NewPingMessage()
// -- you can modifiy the request here
// The following function will subscribe to the 'pong' channel (reply channel
// to PingRequest operation) and wait for a response. The response will be
// detected through its correlation ID. However, if there is no correlation
// ID, then it will return the first message on the reply channel.
//
// Note: it will indefinitely wait for messages as context has no timeout
resp, err := ctrl.RequestToPingRequestOperation(context.Background(), req)
// -- Error management
// Use the response