Add helper functions to extract task metadata from context

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `GetTaskID`, `GetRetryCount`, and `GetMaxRetry` functions were added to extract task metadata from context.
+
 ## [0.9.0] - 2020-05-16
 
 ### Changed

context.go

@@ -0,0 +1,85 @@
+// Copyright 2020 Kentaro Hibino. All rights reserved.
+// Use of this source code is governed by a MIT license
+// that can be found in the LICENSE file.
+
+package asynq
+
+import (
+	"context"
+	"time"
+
+	"github.com/hibiken/asynq/internal/base"
+)
+
+// A taskMetadata holds task scoped data to put in context.
+type taskMetadata struct {
+	id         string
+	maxRetry   int
+	retryCount int
+}
+
+// ctxKey type is unexported to prevent collisions with context keys defined in
+// other packages.
+type ctxKey int
+
+// metadataCtxKey is the context key for the task metadata.
+// Its value of zero is arbitrary.
+const metadataCtxKey ctxKey = 0
+
+// createContext returns a context and cancel function for a given task message.
+func createContext(msg *base.TaskMessage) (ctx context.Context, cancel context.CancelFunc) {
+	metadata := taskMetadata{
+		id:         msg.ID.String(),
+		maxRetry:   msg.Retry,
+		retryCount: msg.Retried,
+	}
+	ctx = context.WithValue(context.Background(), metadataCtxKey, metadata)
+	timeout, err := time.ParseDuration(msg.Timeout)
+	if err == nil && timeout != 0 {
+		ctx, cancel = context.WithTimeout(ctx, timeout)
+	}
+	deadline, err := time.Parse(time.RFC3339, msg.Deadline)
+	if err == nil && !deadline.IsZero() {
+		ctx, cancel = context.WithDeadline(ctx, deadline)
+	}
+	if cancel == nil {
+		ctx, cancel = context.WithCancel(ctx)
+	}
+	return ctx, cancel
+}
+
+// GetTaskID extracts a task ID from a context, if any.
+//
+// ID of a task is guaranteed to be unique.
+// ID of a task doesn't change if the task is being retried.
+func GetTaskID(ctx context.Context) (id string, ok bool) {
+	metadata, ok := ctx.Value(metadataCtxKey).(taskMetadata)
+	if !ok {
+		return "", false
+	}
+	return metadata.id, true
+}
+
+// GetRetryCount extracts retry count from a context, if any.
+//
+// Return value n indicates the number of times associated task has been
+// retried so far.
+func GetRetryCount(ctx context.Context) (n int, ok bool) {
+	metadata, ok := ctx.Value(metadataCtxKey).(taskMetadata)
+	if !ok {
+		return 0, false
+	}
+	return metadata.retryCount, true
+}
+
+// GetMaxRetry extracts maximum retry from a context, if any.
+//
+// Return value n indicates the maximum number of times the assoicated task
+// can be retried if ProcessTask returns a non-nil error.
+func GetMaxRetry(ctx context.Context) (n int, ok bool) {
+	metadata, ok := ctx.Value(metadataCtxKey).(taskMetadata)
+	if !ok {
+		return 0, false
+	}
+	return metadata.maxRetry, true
+}

context_test.go

@@ -0,0 +1,157 @@
+// Copyright 2020 Kentaro Hibino. All rights reserved.
+// Use of this source code is governed by a MIT license
+// that can be found in the LICENSE file.
+
+package asynq
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
+	"github.com/hibiken/asynq/internal/base"
+	"github.com/rs/xid"
+)
+
+func TestCreateContextWithTimeRestrictions(t *testing.T) {
+	var (
+		noTimeout  = time.Duration(0)
+		noDeadline = time.Time{}
+	)
+
+	tests := []struct {
+		desc         string
+		timeout      time.Duration
+		deadline     time.Time
+		wantDeadline time.Time
+	}{
+		{"only with timeout", 10 * time.Second, noDeadline, time.Now().Add(10 * time.Second)},
+		{"only with deadline", noTimeout, time.Now().Add(time.Hour), time.Now().Add(time.Hour)},
+		{"with timeout and deadline (timeout < deadline)", 10 * time.Second, time.Now().Add(time.Hour), time.Now().Add(10 * time.Second)},
+		{"with timeout and deadline (timeout > deadline)", 10 * time.Minute, time.Now().Add(30 * time.Second), time.Now().Add(30 * time.Second)},
+	}
+
+	for _, tc := range tests {
+		msg := &base.TaskMessage{
+			Type:     "something",
+			ID:       xid.New(),
+			Timeout:  tc.timeout.String(),
+			Deadline: tc.deadline.Format(time.RFC3339),
+		}
+
+		ctx, cancel := createContext(msg)
+
+		select {
+		case x := <-ctx.Done():
+			t.Errorf("%s: <-ctx.Done() == %v, want nothing (it should block)", tc.desc, x)
+		default:
+		}
+
+		got, ok := ctx.Deadline()
+		if !ok {
+			t.Errorf("%s: ctx.Deadline() returned false, want deadline to be set", tc.desc)
+		}
+		if !cmp.Equal(tc.wantDeadline, got, cmpopts.EquateApproxTime(time.Second)) {
+			t.Errorf("%s: ctx.Deadline() returned %v, want %v", tc.desc, got, tc.wantDeadline)
+		}
+
+		cancel()
+
+		select {
+		case <-ctx.Done():
+		default:
+			t.Errorf("ctx.Done() blocked, want it to be non-blocking")
+		}
+	}
+}
+
+func TestCreateContextWithoutTimeRestrictions(t *testing.T) {
+	msg := &base.TaskMessage{
+		Type:     "something",
+		ID:       xid.New(),
+		Timeout:  time.Duration(0).String(),        // zero value to indicate no timeout
+		Deadline: time.Time{}.Format(time.RFC3339), // zero value to indicate no deadline
+	}
+
+	ctx, cancel := createContext(msg)
+
+	select {
+	case x := <-ctx.Done():
+		t.Errorf("<-ctx.Done() == %v, want nothing (it should block)", x)
+	default:
+	}
+
+	_, ok := ctx.Deadline()
+	if ok {
+		t.Error("ctx.Deadline() returned true, want deadline to not be set")
+	}
+
+	cancel()
+
+	select {
+	case <-ctx.Done():
+	default:
+		t.Error("ctx.Done() blocked, want it to be non-blocking")
+	}
+}
+
+func TestGetTaskMetadataFromContext(t *testing.T) {
+	tests := []struct {
+		desc string
+		msg  *base.TaskMessage
+	}{
+		{"with zero retried message", &base.TaskMessage{Type: "something", ID: xid.New(), Retry: 25, Retried: 0}},
+		{"with non-zero retried message", &base.TaskMessage{Type: "something", ID: xid.New(), Retry: 10, Retried: 5}},
+	}
+
+	for _, tc := range tests {
+		ctx, _ := createContext(tc.msg)
+
+		id, ok := GetTaskID(ctx)
+		if !ok {
+			t.Errorf("%s: GetTaskID(ctx) returned ok == false", tc.desc)
+		}
+		if ok && id != tc.msg.ID.String() {
+			t.Errorf("%s: GetTaskID(ctx) returned id == %q, want %q", tc.desc, id, tc.msg.ID.String())
+		}
+
+		retried, ok := GetRetryCount(ctx)
+		if !ok {
+			t.Errorf("%s: GetRetryCount(ctx) returned ok == false", tc.desc)
+		}
+		if ok && retried != tc.msg.Retried {
+			t.Errorf("%s: GetRetryCount(ctx) returned n == %d want %d", tc.desc, retried, tc.msg.Retried)
+		}
+
+		maxRetry, ok := GetMaxRetry(ctx)
+		if !ok {
+			t.Errorf("%s: GetMaxRetry(ctx) returned ok == false", tc.desc)
+		}
+		if ok && maxRetry != tc.msg.Retry {
+			t.Errorf("%s: GetMaxRetry(ctx) returned n == %d want %d", tc.desc, maxRetry, tc.msg.Retry)
+		}
+	}
+}
+
+func TestGetTaskMetadataFromContextError(t *testing.T) {
+	tests := []struct {
+		desc string
+		ctx  context.Context
+	}{
+		{"with background context", context.Background()},
+	}
+
+	for _, tc := range tests {
+		if _, ok := GetTaskID(tc.ctx); ok {
+			t.Errorf("%s: GetTaskID(ctx) returned ok == true", tc.desc)
+		}
+		if _, ok := GetRetryCount(tc.ctx); ok {
+			t.Errorf("%s: GetRetryCount(ctx) returned ok == true", tc.desc)
+		}
+		if _, ok := GetMaxRetry(tc.ctx); ok {
+			t.Errorf("%s: GetMaxRetry(ctx) returned ok == true", tc.desc)
+		}
+	}
+}

processor.go

@@ -405,20 +405,3 @@ func gcd(xs ...int) int {
 	}
 	return res
 }
-
-// createContext returns a context and cancel function for a given task message.
-func createContext(msg *base.TaskMessage) (ctx context.Context, cancel context.CancelFunc) {
-	ctx = context.Background()
-	timeout, err := time.ParseDuration(msg.Timeout)
-	if err == nil && timeout != 0 {
-		ctx, cancel = context.WithTimeout(ctx, timeout)
-	}
-	deadline, err := time.Parse(time.RFC3339, msg.Deadline)
-	if err == nil && !deadline.IsZero() {
-		ctx, cancel = context.WithDeadline(ctx, deadline)
-	}
-	if cancel == nil {
-		ctx, cancel = context.WithCancel(ctx)
-	}
-	return ctx, cancel
-}

processor_test.go

@@ -17,7 +17,6 @@ import (
 	h "github.com/hibiken/asynq/internal/asynqtest"
 	"github.com/hibiken/asynq/internal/base"
 	"github.com/hibiken/asynq/internal/rdb"
-	"github.com/rs/xid"
 )
 
 func TestProcessorSuccess(t *testing.T) {
@@ -391,88 +390,6 @@ func TestPerform(t *testing.T) {
 	}
 }
 
-func TestCreateContextWithTimeRestrictions(t *testing.T) {
-	var (
-		noTimeout  = time.Duration(0)
-		noDeadline = time.Time{}
-	)
-
-	tests := []struct {
-		desc         string
-		timeout      time.Duration
-		deadline     time.Time
-		wantDeadline time.Time
-	}{
-		{"only with timeout", 10 * time.Second, noDeadline, time.Now().Add(10 * time.Second)},
-		{"only with deadline", noTimeout, time.Now().Add(time.Hour), time.Now().Add(time.Hour)},
-		{"with timeout and deadline (timeout < deadline)", 10 * time.Second, time.Now().Add(time.Hour), time.Now().Add(10 * time.Second)},
-		{"with timeout and deadline (timeout > deadline)", 10 * time.Minute, time.Now().Add(30 * time.Second), time.Now().Add(30 * time.Second)},
-	}
-
-	for _, tc := range tests {
-		msg := &base.TaskMessage{
-			Type:     "something",
-			ID:       xid.New(),
-			Timeout:  tc.timeout.String(),
-			Deadline: tc.deadline.Format(time.RFC3339),
-		}
-
-		ctx, cancel := createContext(msg)
-
-		select {
-		case x := <-ctx.Done():
-			t.Errorf("%s: <-ctx.Done() == %v, want nothing (it should block)", tc.desc, x)
-		default:
-		}
-
-		got, ok := ctx.Deadline()
-		if !ok {
-			t.Errorf("%s: ctx.Deadline() returned false, want deadline to be set", tc.desc)
-		}
-		if !cmp.Equal(tc.wantDeadline, got, cmpopts.EquateApproxTime(time.Second)) {
-			t.Errorf("%s: ctx.Deadline() returned %v, want %v", tc.desc, got, tc.wantDeadline)
-		}
-
-		cancel()
-
-		select {
-		case <-ctx.Done():
-		default:
-			t.Errorf("ctx.Done() blocked, want it to be non-blocking")
-		}
-	}
-}
-
-func TestCreateContextWithoutTimeRestrictions(t *testing.T) {
-	msg := &base.TaskMessage{
-		Type:     "something",
-		ID:       xid.New(),
-		Timeout:  time.Duration(0).String(),        // zero value to indicate no timeout
-		Deadline: time.Time{}.Format(time.RFC3339), // zero value to indicate no deadline
-	}
-
-	ctx, cancel := createContext(msg)
-
-	select {
-	case x := <-ctx.Done():
-		t.Errorf("<-ctx.Done() == %v, want nothing (it should block)", x)
-	default:
-	}
-
-	_, ok := ctx.Deadline()
-	if ok {
-		t.Error("ctx.Deadline() returned true, want deadline to not be set")
-	}
-
-	cancel()
-
-	select {
-	case <-ctx.Done():
-	default:
-		t.Error("ctx.Done() blocked, want it to be non-blocking")
-	}
-}
-
 func TestGCD(t *testing.T) {
 	tests := []struct {
 		input []int