Application Start

Recall that our program's entrypoint finishes with initializing the app struct and calling the app.Start(ctx) function. The Start function is a place where we start the application's lifecycle.

greeter/app.go

func (a *App) Start(ctx context.Context) {
    go a.receiveConfigNotifications(ctx)

    for {
        select {
        case <-a.configReceivedCh:
            a.logger.Info().Msg("Received full config")

            a.processConfig(ctx)

            a.updateState(ctx)

        case <-ctx.Done():
            a.stop()
            return
        }
    }
}

The Start function is composed of the following parts:

1. Start receiving configuration notifications with receiveConfigNotifications function. In this function we:
   1. Start Configuration Stream
   2. Receive notifications from the stream
   3. When the configuration notification is received, unmarshal received config into the ConfigState struct
   4. Upon "commit.end" marker seen in the config notification, signal that the whole config set has been read by sending a message to the receivedCh channel
2. Process the configuration by computing the greeting value
3. Update application's state by with name and greeting values
4. Stop the application when the context is cancelled

Time to have a closer look at the first part of the Start function - receiving configuration notifications with go a.receiveConfigNotifications(ctx) function.

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