feat: use publish/subscribe for tasks

client/client.go

@@ -7,13 +7,26 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"sync"
 	"time"
 )
 
+type SubscriberFunc func(*Task) error
+
 // Client wraps HTTP calls to the task queue service.
 type Client struct {
 	BaseURL       string
 	HTTPClient    *http.Client
+	ApplicationID string
+	WorkerID      string
+
+	mu          sync.Mutex
+	subscribers map[string]map[int]SubscriberFunc
+	nextID      int
+
+	ctx     context.Context
+	cancel  context.CancelFunc
+	running bool
 }
 
 type TaskFilter struct {
@@ -23,6 +36,7 @@ type TaskFilter struct {
 type Task struct {
 	ID            string      `json:"id"`
 	ApplicationId string      `json:"applicationId"`
+	EventID       string      `json:"eventId"`
 	Payload       interface{} `json:"payload"`
 	Priority      int         `json:"priority"`
 	AvailableAt   time.Time   `json:"availableAt"`
@@ -52,14 +66,19 @@ func (t *Task) ParsePayload(v interface{}) error {
 	return nil
 }
 
-type EnqueueRequest struct {
-	ApplicationId string      `json:"applicationId"`
-	Payload       interface{} `json:"payload"`
+type EnqueueOptions struct {
 	Priority    int `json:"priority"`
 	DelaySec    int `json:"delaySec"`
 	MaxAttempts int `json:"maxAttempts"`
 }
 
+type EnqueueRequest struct {
+	ApplicationId string      `json:"applicationId"`
+	EventID       string      `json:"eventId"`
+	Payload       interface{} `json:"payload"`
+	EnqueueOptions
+}
+
 type PopRequest struct {
 	WorkerId     string      `json:"workerId"`
 	LeaseSeconds int         `json:"leaseSeconds"`
@@ -82,19 +101,24 @@ type RequeueRequest struct {
 	WorkerId     string   `json:"workerId"`
 	TaskId       string   `json:"taskId"`
 	DelaySeconds int      `json:"delaySec"`
-	Error        string `json:"error"`
+	Errors       []string `json:"errors"`
 }
 
 // New creates a new client.
-func New(baseURL string) *Client {
+func New(baseURL string, ApplicationID string, WorkerId string) *Client {
 	return &Client{
 		BaseURL:       baseURL,
 		HTTPClient:    &http.Client{Timeout: 10 * time.Second},
+		subscribers:   make(map[string]map[int]SubscriberFunc),
+		ApplicationID: ApplicationID,
+		WorkerID:      WorkerId,
 	}
 }
 
 // Enqueue adds a new task.
-func (c *Client) Enqueue(ctx context.Context, request *EnqueueRequest) (*Task, error) {
+func (c *Client) enqueue(ctx context.Context, request *EnqueueRequest) (*Task, error) {
+	request.ApplicationId = c.ApplicationID
+
 	var t Task
 	if err := c.do(ctx, "POST", "/enqueue", request, &t); err != nil {
 		return nil, err
@@ -103,7 +127,7 @@ func (c *Client) Enqueue(ctx context.Context, request *EnqueueRequest) (*Task, e
 }
 
 // Pop leases a task.
-func (c *Client) Pop(ctx context.Context, request *PopRequest) (*Task, bool, error) {
+func (c *Client) pop(ctx context.Context, request *PopRequest) (*Task, bool, error) {
 
 	var t Task
 	status, err := c.doStatus(ctx, "POST", "/pop", request, &t)
@@ -119,7 +143,11 @@ func (c *Client) Pop(ctx context.Context, request *PopRequest) (*Task, bool, err
 }
 
 // Complete marks a task as done.
-func (c *Client) Complete(ctx context.Context, request *CompleteRequest) error {
+func (c *Client) complete(ctx context.Context, TaskId string) error {
+	request := &CompleteRequest{
+		WorkerId: c.WorkerID,
+		TaskId:   TaskId,
+	}
 	return c.doNoResp(ctx, "POST", "/complete", request)
 }
 
@@ -129,7 +157,7 @@ func (c *Client) Extend(ctx context.Context, request *ExtendRequest) error {
 }
 
 // Requeue returns a task to the queue.
-func (c *Client) Requeue(ctx context.Context, request *RequeueRequest) error {
+func (c *Client) requeue(ctx context.Context, request *RequeueRequest) error {
 	return c.doNoResp(ctx, "POST", "/requeue", request)
 }
 
@@ -185,3 +213,146 @@ func (c *Client) doStatus(ctx context.Context, method, path string, body interfa
 	}
 	return resp.StatusCode, nil
 }
+
+func (c *Client) Publish(eventId string, payload interface{}, opts *EnqueueOptions) error {
+
+	_, err := c.enqueue(context.Background(), &EnqueueRequest{
+		EventID:        eventId,
+		Payload:        payload,
+		EnqueueOptions: *opts,
+	})
+	if err != nil {
+		return fmt.Errorf("error enqueuing task with error: %s", err.Error())
+	}
+
+	return nil
+}
+
+func (c *Client) Subscribe(event string, fn SubscriberFunc) int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.subscribers[event] == nil {
+		c.subscribers[event] = make(map[int]SubscriberFunc)
+	}
+
+	id := c.nextID
+	c.nextID++
+	c.subscribers[event][id] = fn
+
+	if !c.running {
+		c.startPolling()
+	}
+
+	return id
+}
+
+func (c *Client) Unsubscribe(event string, id int) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if subs, ok := c.subscribers[event]; ok {
+		delete(subs, id)
+		if len(subs) == 0 {
+			delete(c.subscribers, event)
+		}
+	}
+
+	if len(c.subscribers) == 0 && c.running {
+		c.stopPolling()
+	}
+}
+
+func (c *Client) startPolling() {
+	c.ctx, c.cancel = context.WithCancel(context.Background())
+	c.running = true
+
+	go c.pollLoop()
+}
+
+func (c *Client) stopPolling() {
+	c.cancel()
+	c.running = false
+}
+
+func (c *Client) pollLoop() {
+	ticker := time.NewTicker(1 * time.Second)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-c.ctx.Done():
+			return
+		case <-ticker.C:
+			c.pollServer()
+		}
+	}
+}
+
+func (c *Client) pollServer() {
+	task, ok, err := c.pop(c.ctx, &PopRequest{
+		WorkerId:     c.WorkerID,
+		LeaseSeconds: 60,
+		Filter: &TaskFilter{
+			ApplicationId: c.ApplicationID,
+		},
+	})
+	if err != nil || !ok {
+		if err != nil {
+			fmt.Println(err.Error())
+		}
+		return
+	}
+
+	// snapshot subscribers
+	c.mu.Lock()
+	subscribers := c.subscribers[task.EventID]
+	c.mu.Unlock()
+
+	if len(subscribers) == 0 {
+		return
+	}
+
+	var (
+		wg   sync.WaitGroup
+		errs []error
+		mu   sync.Mutex
+	)
+
+	for _, fn := range subscribers {
+		wg.Add(1)
+
+		go func(fn SubscriberFunc) {
+			defer wg.Done()
+
+			if err := fn(task); err != nil {
+				mu.Lock()
+				errs = append(errs, err)
+				mu.Unlock()
+			}
+		}(fn)
+	}
+
+	wg.Wait()
+
+	ctx := context.Background()
+
+	if len(errs) > 0 {
+		errors := make([]string, 0)
+		for _, err := range errs {
+			if err != nil {
+				errors = append(errors, err.Error())
+			}
+		}
+
+		c.requeue(ctx, &RequeueRequest{
+			TaskId:       task.ID,
+			WorkerId:     c.WorkerID,
+			DelaySeconds: 5,
+			Errors:       errors,
+		})
+		return
+	}
+
+	c.complete(ctx, task.ID)
+}

client/client_test.go

@@ -1,10 +1,12 @@
 package client
 
 import (
-	"context"
+	"errors"
 	"fmt"
 	"log"
 	"os"
+	"os/signal"
+	"syscall"
 	"testing"
 )
 
@@ -18,42 +20,9 @@ func TestClient(t *testing.T) {
 
 	workerId, _ := os.Hostname()
 
-	client := New("http://localhost:10101")
-	ctx := context.Background()
+	client := New("http://10.10.10.2:10101", "email", workerId)
 
-	newEmailPayload := EmailPayload{
-		To:      "example@example.com",
-		Subject: "Test",
-		Body:    "Hello World",
-	}
-
-	// Enqueue a task
-	task, err := client.Enqueue(ctx, &EnqueueRequest{
-		ApplicationId: "email",
-		Payload:       newEmailPayload,
-		Priority:      10,
-		DelaySec:      0,
-		MaxAttempts:   5,
-	})
-	if err != nil {
-		log.Fatal("enqueue:", err)
-	}
-	fmt.Println("Enqueued task:", task.ID)
-
-	// Pop a task
-	task, ok, err := client.Pop(ctx, &PopRequest{
-		WorkerId:     workerId,
-		LeaseSeconds: 60,
-		Filter:       &TaskFilter{ApplicationId: "email"},
-		MinPriority:  0,
-	})
-	if err != nil {
-		log.Fatal("pop:", err)
-	}
-	if !ok {
-		fmt.Println("No tasks available")
-		return
-	}
+	subID := client.Subscribe("send.email", func(task *Task) error {
 
 		// Parse payload into struct
 		var email EmailPayload
@@ -62,9 +31,44 @@ func TestClient(t *testing.T) {
 		}
 		fmt.Printf("Got email task: %+v\n", email)
 
-	// Mark task as complete
-	if err := client.Complete(ctx, &CompleteRequest{TaskId: task.ID, WorkerId: workerId}); err != nil {
-		log.Fatal("complete:", err)
+		fmt.Println("Task 1 completed")
+
+		return nil
+	})
+
+	subID2 := client.Subscribe("send.email", func(task *Task) error {
+
+		return errors.New("Test Error")
+	})
+
+	newEmailPayload := EmailPayload{
+		To:      "example@example.com",
+		Subject: "Test",
+		Body:    "Hello World",
 	}
-	fmt.Println("Task completed")
+
+	// Enqueue a task
+	err := client.Publish("send.email", newEmailPayload, &EnqueueOptions{
+		Priority:    10,
+		DelaySec:    0,
+		MaxAttempts: 5,
+	})
+	if err != nil {
+		log.Fatal("enqueue:", err)
+	}
+	fmt.Println("Enqueued task")
+
+	// Block until SIGINT or SIGTERM
+	sigChan := make(chan os.Signal, 1)
+	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
+
+	<-sigChan
+
+	fmt.Println("\nShutting down...")
+
+	// Unsubscribe so polling stops
+	client.Unsubscribe("send.email", subID)
+	client.Unsubscribe("send.email", subID2)
+
+	fmt.Println("Clean exit.")
 }