Allow common redis and leveldb connections (#12385)

* Allow common redis and leveldb connections

Prevents multiple reopening of redis and leveldb connections to the same
place by sharing connections.

Further allows for more configurable redis connection type using the
redisURI and a leveldbURI scheme.

Signed-off-by: Andrew Thornton <art27@cantab.net>

* add unit-test

Signed-off-by: Andrew Thornton <art27@cantab.net>

* as per @lunny

Signed-off-by: Andrew Thornton <art27@cantab.net>

* add test

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Update modules/cache/cache_redis.go

* Update modules/queue/queue_disk.go

* Update modules/cache/cache_redis.go

* Update modules/cache/cache_redis.go

* Update modules/queue/unique_queue_disk.go

* Update modules/queue/queue_disk.go

* Update modules/queue/unique_queue_disk.go

* Update modules/session/redis.go

Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: Lauris BH <lauris@nix.lv>

modules/nosql/manager.go

@@ -0,0 +1,71 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package nosql
+
+import (
+	"strconv"
+	"sync"
+	"time"
+
+	"github.com/go-redis/redis/v7"
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+var manager *Manager
+
+// Manager is the nosql connection manager
+type Manager struct {
+	mutex sync.Mutex
+
+	RedisConnections   map[string]*redisClientHolder
+	LevelDBConnections map[string]*levelDBHolder
+}
+
+type redisClientHolder struct {
+	redis.UniversalClient
+	name  []string
+	count int64
+}
+
+func (r *redisClientHolder) Close() error {
+	return manager.CloseRedisClient(r.name[0])
+}
+
+type levelDBHolder struct {
+	name  []string
+	count int64
+	db    *leveldb.DB
+}
+
+func init() {
+	_ = GetManager()
+}
+
+// GetManager returns a Manager and initializes one as singleton is there's none yet
+func GetManager() *Manager {
+	if manager == nil {
+		manager = &Manager{
+			RedisConnections:   make(map[string]*redisClientHolder),
+			LevelDBConnections: make(map[string]*levelDBHolder),
+		}
+	}
+	return manager
+}
+
+func valToTimeDuration(vs []string) (result time.Duration) {
+	var err error
+	for _, v := range vs {
+		result, err = time.ParseDuration(v)
+		if err != nil {
+			var val int
+			val, err = strconv.Atoi(v)
+			result = time.Duration(val)
+		}
+		if err == nil {
+			return
+		}
+	}
+	return
+}