Google Cloud Pubsub

This package wraps the google cloud pubsub logic into two seperate part. A consumer package and a publisher package.

The Package provides testing support, so all you have to do is focuse on the business values, without any fuss of emulated environment and other stuffs like that.

Dependencies

go get -u cloud.google.com/go/pubsub

Install

go get -u github.com/adamluzsi/GoogleCloudPubsub

Consumer

Usage

First of all, you need a Handler struct that will implement the business logic for the Gcloud pubsub subscription consuming:

type ExampleHandler struct {
    // you can use use fields to store messages if you want for example bulk processing
	// messages []consumer.Message
}

// HandleMessage method will be called after a message had beed fetched from the pubsub.
// return error will Nack the message
func (eh *ExampleHandler) HandleMessage(msg consumer.Message) error {
	// eh.messages = append(eh.messages, msg)
    // single element processing can be implemented here
    return nil
}

// Finish method will be called before all messages should be acked
// With this method, you can do bulk actions after the HandleMessage Collected all the elements
func (eh *ExampleHandler) Finish() error {
	defer eh.wg.Done()
    // heavy bulk actions can be implemented here
	return nil
}

// The return value should be the consumer.Handler interface,
// not the actual struct pointer
func NewExampleHandler() consumer.Handler {
    return &ExampleHandler{}
}

Now with your new fancy struct and with it's constructor function, you can begin to use the Consumer

ctx := context.Background()
c := consumer.New(ctx, "example-subscription-name", NewExampleHandler)

If you want to specify further options for the consumer, you can do so with option setters.

ctx := context.Background()
cons := consumer.New(ctx, "example", NewExampleHandler,
        // you can configure the new consumer to use given amount of BatchSize
        // This is the amount that will be passed for the HandleMessage method for a single Handler object
		consumer.SetBatchSizeTo(amount),

        // This will set the Google Pubsub Message Iterators MaxExtensionDuration
		consumer.SetMaxExtensionDurationTo(10*time.Minute),

        // This will configure the consumer to how manny parallel worker should pull from the subscription
		consumer.SetWorkersCountTo(runtime.NumCPU()))

Testing

When You test your application, Before the Consumer is being initialized, you should turn on Mock mod. When Mock mod enabled, not the original but a Mock consumer will be created when the New method called. It's behavior is alike, but remove the Dependency to use Google Pubsub Emulated Host, and increase the speed for your tests.

Make even the Benchmarking more valuable

func TestConsumerMockingAllPerfect(t *testing.T) {
	consumer.TurnMockModOn()
	defer consumer.TurnMockModOff()

    // consumer creation is the same, and not required to be happen here,
    // this is just an example , that it should be created after the mock mod enabled
    ctx := context.Background()
    c := consumer.New(ctx, "example-subscription-name", NewExampleHandler)
    c.Start()
    defer c.Stop()

    // And this is how you Send Messages to the Mock Consumer
    consumer.MockMessageFeeder["example-subscription-name"] <- []byte(`Hello World!`)

    // super complex business logic testing here

}

Publisher

Usage

Now with your new fancy struct and with it's constructor function, you can begin to use the Consumer

import "github.com/adamluzsi/GoogleCloudPubsub/publisher"
//...

ctx := context.Background()
p := publisher.New(ctx, "my-example-topic-name")
p.Publish([]byte(`hello world!`))
p.Publish([]byte(`hello`), []byte(`world`))

Testing

Publisher also support mock mod

func TestMockedPublishing(t *testing.T) {

    publisher.TurnMockModOn()
	defer publisher.TurnMockModOff()
	ctx := context.Background()

    p := publisher.New(ctx, TopicName)
	p.Publish([]byte(`hello world!`))
	p.Publish([]byte(`hello`), []byte(`world`))

	datas := make([][]byte, 0, 3)

	for i := 0; i < 3; i++ {
		data := <- publisher.MockMessageReceiver[TopicName]
		datas = append(datas, data)
	}

}