Machine

import "github.com/autom8ter/machine/v3"

Machine is a zero dependency library for highly concurrent Go applications. It is inspired by errgroup.Group with extra bells & whistles:

• In memory Publish Subscribe for asynchronously broadcasting & consuming messages in memory
• Asynchronous worker groups similar to errgroup.Group
• Throttled max active goroutine count
• Asynchronous error handling(see WithErrorHandler to override default error handler)
• Asynchronous cron jobs- Cron()

Use Cases

Machine is meant to be completely agnostic and dependency free- its use cases are expected to be emergent. Really, it can be used anywhere goroutines are used.

Highly concurrent and/or asynchronous applications include:

• gRPC streaming servers

• websocket servers

• pubsub servers

• reverse proxies

• cron jobs

• custom database/cache

• ETL pipelines

• log sink

• filesystem walker

• code generation

// Machine is an interface for highly asynchronous Go applications
type Machine interface {
// Publish synchronously publishes the Message
Publish(ctx context.Context, msg Message)
// Subscribe synchronously subscribes to messages on a given channel,  executing the given HandlerFunc UNTIL the context cancels OR false is returned by the HandlerFunc.
// Glob matching IS supported for subscribing to multiple channels at once.
Subscribe(ctx context.Context, channel string, handler MessageHandlerFunc, opts ...SubscriptionOpt)
// Subscribers returns total number of subscribers to the given channel
Subscribers(channel string) int
// Channels returns the channel names that messages have been sent to
Channels() []string
// Go asynchronously executes the given Func
Go(ctx context.Context, fn Func)
// Cron asynchronously executes the given function on a timed interval UNTIL the context cancels OR false is returned by the CronFunc
Cron(ctx context.Context, interval time.Duration, fn CronFunc)
// Current returns the number of active jobs that are running concurrently
Current() int
// Wait blocks until all active async functions(Go, Cron) exit
Wait()
// Close blocks until all active routine's exit(calls Wait) then closes all active subscriptions
Close()
}

Example

        ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
  	defer cancel()
  	var (
  		m       = machine.New()
  		results []string
  		mu      sync.RWMutex
  	)
  	defer m.Close()
  
  	m.Go(ctx, func(ctx context.Context) error {
  		m.Subscribe(ctx, "accounting.*", func(ctx context.Context, msg machine.Message) (bool, error) {
  			mu.Lock()
  			results = append(results, fmt.Sprintf("(%s) received msg: %v\n", msg.Channel, msg.Body))
  			mu.Unlock()
  			return true, nil
  		})
  		return nil
  	})
  	m.Go(ctx, func(ctx context.Context) error {
  		m.Subscribe(ctx, "engineering.*", func(ctx context.Context, msg machine.Message) (bool, error) {
  			mu.Lock()
  			results = append(results, fmt.Sprintf("(%s) received msg: %v\n", msg.Channel, msg.Body))
  			mu.Unlock()
  			return true, nil
  		})
  		return nil
  	})
  	m.Go(ctx, func(ctx context.Context) error {
  		m.Subscribe(ctx, "human_resources.*", func(ctx context.Context, msg machine.Message) (bool, error) {
  			mu.Lock()
  			results = append(results, fmt.Sprintf("(%s) received msg: %v\n", msg.Channel, msg.Body))
  			mu.Unlock()
  			return true, nil
  		})
  		return nil
  	})
  	m.Go(ctx, func(ctx context.Context) error {
  		m.Subscribe(ctx, "*", func(ctx context.Context, msg machine.Message) (bool, error) {
  			mu.Lock()
  			results = append(results, fmt.Sprintf("(%s) received msg: %v\n", msg.Channel, msg.Body))
  			mu.Unlock()
  			return true, nil
  		})
  		return nil
  	})
  	<-time.After(1 * time.Second)
  	m.Publish(ctx, machine.Message{
  		Channel: "human_resources.chat_room6",
  		Body:    "hello world human resources",
  	})
  	m.Publish(ctx, machine.Message{
  		Channel: "accounting.chat_room2",
  		Body:    "hello world accounting",
  	})
  	m.Publish(ctx, machine.Message{
  		Channel: "engineering.chat_room1",
  		Body:    "hello world engineering",
  	})
  	m.Wait()
  	sort.Strings(results)
  	for _, res := range results {
  		fmt.Print(res)
  	}
  	// Output:
  	//(accounting.chat_room2) received msg: hello world accounting
  	//(accounting.chat_room2) received msg: hello world accounting
  	//(engineering.chat_room1) received msg: hello world engineering
  	//(engineering.chat_room1) received msg: hello world engineering
  	//(human_resources.chat_room6) received msg: hello world human resources
  	//(human_resources.chat_room6) received msg: hello world human resources

Extended Examples

All examples are < 500 lines of code(excluding code generation)

• gRPC Bidirectional Chat Stream Server
• Concurrent Cron Job Server
• TCP Reverse Proxy