Use global lock instead of NewExclusivePool to allow distributed lock between multiple Gitea instances (#31813)

Replace #26486 
Fix #19620

---------

Co-authored-by: Jason Song <i@wolfogre.com>

modules/globallock/globallock.go

@@ -6,14 +6,22 @@ package globallock
 import (
 	"context"
 	"sync"
+
+	"code.gitea.io/gitea/modules/setting"
 )
 
 var (
 	defaultLocker Locker
 	initOnce      sync.Once
 	initFunc      = func() {
-		// TODO: read the setting and initialize the default locker.
-		//       Before implementing this, don't use it.
+		switch setting.GlobalLock.ServiceType {
+		case "redis":
+			defaultLocker = NewRedisLocker(setting.GlobalLock.ServiceConnStr)
+		case "memory":
+			fallthrough
+		default:
+			defaultLocker = NewMemoryLocker()
+		}
 	} // define initFunc as a variable to make it possible to change it in tests
 )
 

modules/setting/gloabl_lock.go

@@ -0,0 +1,37 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/nosql"
+)
+
+// GlobalLock represents configuration of global lock
+var GlobalLock = struct {
+	ServiceType    string
+	ServiceConnStr string
+}{
+	ServiceType: "memory",
+}
+
+func loadGlobalLockFrom(rootCfg ConfigProvider) {
+	sec := rootCfg.Section("global_lock")
+	GlobalLock.ServiceType = sec.Key("SERVICE_TYPE").MustString("memory")
+	switch GlobalLock.ServiceType {
+	case "memory":
+	case "redis":
+		connStr := sec.Key("SERVICE_CONN_STR").String()
+		if connStr == "" {
+			log.Fatal("SERVICE_CONN_STR is empty for redis")
+		}
+		u := nosql.ToRedisURI(connStr)
+		if u == nil {
+			log.Fatal("SERVICE_CONN_STR %s is not a valid redis connection string", connStr)
+		}
+		GlobalLock.ServiceConnStr = connStr
+	default:
+		log.Fatal("Unknown sync lock service type: %s", GlobalLock.ServiceType)
+	}
+}

modules/setting/global_lock_test.go

@@ -0,0 +1,35 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestLoadGlobalLockConfig(t *testing.T) {
+	t.Run("DefaultGlobalLockConfig", func(t *testing.T) {
+		iniStr := ``
+		cfg, err := NewConfigProviderFromData(iniStr)
+		assert.NoError(t, err)
+
+		loadGlobalLockFrom(cfg)
+		assert.EqualValues(t, "memory", GlobalLock.ServiceType)
+	})
+
+	t.Run("RedisGlobalLockConfig", func(t *testing.T) {
+		iniStr := `
+[global_lock]
+SERVICE_TYPE = redis
+SERVICE_CONN_STR = addrs=127.0.0.1:6379 db=0
+`
+		cfg, err := NewConfigProviderFromData(iniStr)
+		assert.NoError(t, err)
+
+		loadGlobalLockFrom(cfg)
+		assert.EqualValues(t, "redis", GlobalLock.ServiceType)
+		assert.EqualValues(t, "addrs=127.0.0.1:6379 db=0", GlobalLock.ServiceConnStr)
+	})
+}

modules/setting/setting.go

@@ -147,6 +147,7 @@ func loadCommonSettingsFrom(cfg ConfigProvider) error {
 	loadGitFrom(cfg)
 	loadMirrorFrom(cfg)
 	loadMarkupFrom(cfg)
+	loadGlobalLockFrom(cfg)
 	loadOtherFrom(cfg)
 	return nil
 }

modules/sync/exclusive_pool.go

@@ -1,69 +0,0 @@
-// Copyright 2016 The Gogs Authors. All rights reserved.
-// SPDX-License-Identifier: MIT
-
-package sync
-
-import (
-	"sync"
-)
-
-// ExclusivePool is a pool of non-identical instances
-// that only one instance with same identity is in the pool at a time.
-// In other words, only instances with different identities can be in
-// the pool the same time. If another instance with same identity tries
-// to get into the pool, it hangs until previous instance left the pool.
-//
-// This pool is particularly useful for performing tasks on same resource
-// on the file system in different goroutines.
-type ExclusivePool struct {
-	lock sync.Mutex
-
-	// pool maintains locks for each instance in the pool.
-	pool map[string]*sync.Mutex
-
-	// count maintains the number of times an instance with same identity checks in
-	// to the pool, and should be reduced to 0 (removed from map) by checking out
-	// with same number of times.
-	// The purpose of count is to delete lock when count down to 0 and recycle memory
-	// from map object.
-	count map[string]int
-}
-
-// NewExclusivePool initializes and returns a new ExclusivePool object.
-func NewExclusivePool() *ExclusivePool {
-	return &ExclusivePool{
-		pool:  make(map[string]*sync.Mutex),
-		count: make(map[string]int),
-	}
-}
-
-// CheckIn checks in an instance to the pool and hangs while instance
-// with same identity is using the lock.
-func (p *ExclusivePool) CheckIn(identity string) {
-	p.lock.Lock()
-
-	lock, has := p.pool[identity]
-	if !has {
-		lock = &sync.Mutex{}
-		p.pool[identity] = lock
-	}
-	p.count[identity]++
-
-	p.lock.Unlock()
-	lock.Lock()
-}
-
-// CheckOut checks out an instance from the pool and releases the lock
-// to let other instances with same identity to grab the lock.
-func (p *ExclusivePool) CheckOut(identity string) {
-	p.lock.Lock()
-	defer p.lock.Unlock()
-
-	p.pool[identity].Unlock()
-	if p.count[identity] == 1 {
-		delete(p.pool, identity)
-		delete(p.count, identity)
-	} else {
-		p.count[identity]--
-	}
-}