Move unique key generator function to base

internal/base/base.go

@@ -9,6 +9,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"sort"
 	"strings"
 	"sync"
 	"time"
@@ -90,6 +91,35 @@ func WorkersKey(hostname string, pid int, sid string) string {
 	return fmt.Sprintf("asynq:workers:{%s:%d:%s}", hostname, pid, sid)
 }
 
+// UniqueKey returns a redis key with the given type, payload, and queue name.
+func UniqueKey(qname, tasktype string, payload map[string]interface{}) string {
+	return fmt.Sprintf("asynq:{%s}:unique:%s:%s", qname, tasktype, serializePayload(payload))
+}
+
+func serializePayload(payload map[string]interface{}) string {
+	if payload == nil {
+		return "nil"
+	}
+	type entry struct {
+		k string
+		v interface{}
+	}
+	var es []entry
+	for k, v := range payload {
+		es = append(es, entry{k, v})
+	}
+	// sort entries by key
+	sort.Slice(es, func(i, j int) bool { return es[i].k < es[j].k })
+	var b strings.Builder
+	for _, e := range es {
+		if b.Len() > 0 {
+			b.WriteString(",")
+		}
+		b.WriteString(fmt.Sprintf("%s=%v", e.k, e.v))
+	}
+	return b.String()
+}
+
 // TaskMessage is the internal representation of a task with additional metadata fields.
 // Serialized data of this type gets written to redis.
 type TaskMessage struct {

internal/base/base_test.go

@@ -212,6 +212,63 @@ func TestWorkersKey(t *testing.T) {
 	}
 }
 
+func TestUniqueKey(t *testing.T) {
+	tests := []struct {
+		desc     string
+		qname    string
+		tasktype string
+		payload  map[string]interface{}
+		want     string
+	}{
+		{
+			"with primitive types",
+			"default",
+			"email:send",
+			map[string]interface{}{"a": 123, "b": "hello", "c": true},
+			"asynq:{default}:unique:email:send:a=123,b=hello,c=true",
+		},
+		{
+			"with unsorted keys",
+			"default",
+			"email:send",
+			map[string]interface{}{"b": "hello", "c": true, "a": 123},
+			"asynq:{default}:unique:email:send:a=123,b=hello,c=true",
+		},
+		{
+			"with composite types",
+			"default",
+			"email:send",
+			map[string]interface{}{
+				"address": map[string]string{"line": "123 Main St", "city": "Boston", "state": "MA"},
+				"names":   []string{"bob", "mike", "rob"}},
+			"asynq:{default}:unique:email:send:address=map[city:Boston line:123 Main St state:MA],names=[bob mike rob]",
+		},
+		{
+			"with complex types",
+			"default",
+			"email:send",
+			map[string]interface{}{
+				"time":     time.Date(2020, time.July, 28, 0, 0, 0, 0, time.UTC),
+				"duration": time.Hour},
+			"asynq:{default}:unique:email:send:duration=1h0m0s,time=2020-07-28 00:00:00 +0000 UTC",
+		},
+		{
+			"with nil payload",
+			"default",
+			"reindex",
+			nil,
+			"asynq:{default}:unique:reindex:nil",
+		},
+	}
+
+	for _, tc := range tests {
+		got := UniqueKey(tc.qname, tc.tasktype, tc.payload)
+		if got != tc.want {
+			t.Errorf("%s: UniqueKey(%q, %q, %v) = %q, want %q", tc.desc, tc.qname, tc.tasktype, tc.payload, got, tc.want)
+		}
+	}
+}
+
 func TestMessageEncoding(t *testing.T) {
 	id := uuid.New()
 	tests := []struct {