基于MongoDB打造.Net的分布式Session子系統

作者：Aaron Dai 2013-08-29 13:46:18

Taobao有她自己的分布式session框架，.net陣營也不能落后了，在下做了個基于MongoDB的支持最多26臺MongoDB的分布式Session框架。

先看看配置文件：

<?xml version="1.0" encoding="utf-8" ?> 
<MongoDBSession> 
  <DbName>SessionDB</DbName> 
  <IdentityMap Identity="A">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="B">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="C">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="D">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="E">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="F">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="G">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="H">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="I">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="J">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="K">mongodb://localhost</IdentityMap>  
  <IdentityMap Identity="L">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="M">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="N">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="O">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="P">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="Q">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="R">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="S">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="T">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="U">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="V">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="W">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="X">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="Y">mongodb://localhost</IdentityMap> 
  <IdentityMap Identity="Z">mongodb://localhost</IdentityMap> 
</MongoDBSession>

從Identity A一直到Z，默認分成了26個Map，具體的C#應用代碼：

protected void btnTest_Click(object sender, EventArgs e)  
        {  
            Session["A"] = DateTime.Now;  
            Session["B"] = 1111111111111;  
            Session["C"] = "fffffffffffffff";  
        }  
 
        protected void btnGetSession_Click(object sender, EventArgs e)  
        {  
            Response.Write(Session["A"].ToString());  
            Response.Write("<br />");  
            Response.Write(Session["B"].ToString());  
            Response.Write("<br />");  
            Response.Write(Session["C"].ToString());  
        }  
        protected void btnAbandon_Click(object sender, EventArgs e)  
        {  
            Session.Abandon();  
        }

呵呵，就是普通的Session用法。

這個要配置web.config：

<system.web> 
    <sessionState mode="Custom" customProvider="A2DSessionProvider" sessionIDManagerType="A2DFramework.SessionService.MongoDBSessionIDManager"> 
      <providers> 
        <add name="A2DSessionProvider" type="A2DFramework.SessionService.MongoDBSessionStateStore"/> 
      </providers> 
    </sessionState> 
  </system.web>

這里會牽扯出2個類：

A2DFramework.SessionService.MongoDBSessionIDManager
A2DFramework.SessionService.MongoDBSessionStateStore

MongoDBSessionIDManager

自定義生成的cookie值（也就是SessionID），在這個sample中，會生成如“E.asadfalkasdfjal”這樣的SessionID，其中前綴E代表這個Session的信息會映射到哪臺MongoDB上。
關鍵代碼

public class MongoDBSessionIDManager : SessionIDManager  
    {  
        private Random rnd = new Random();  
        private object oLock = new object();  
 
        public override string CreateSessionID(System.Web.HttpContext context)  
        {  
            int index = 0;  
            lock(this.oLock)  
            {  
                index = rnd.Next(SessionConfiguration.SessionServerIdentities.Length);  
            }  
            string sessionId = string.Format("{0}.{1}", SessionConfiguration.SessionServerIdentities[index], base.CreateSessionID(context));  
            return sessionId;  
        }  
 
        public override string Encode(string id)  
        {  
            return DESEncryptor.Encode(id, SessionConfiguration.DESKey);  
        }  
        public override string Decode(string id)  
        {  
            return DESEncryptor.Decode(id, SessionConfiguration.DESKey);  
        }  
 
        public override bool Validate(string id)  
        {  
            string prefix;  
            string realId;  
 
            if (!Helper.ParseSessionID(id, out prefix, out realId))  
                return false;  
 
            return base.Validate(realId);  
        }  
    }

#p#

MongoDBSessionStateStore

自定義Session過程中最核心的一個類，代碼如下（較多）：

public sealed class MongoDBSessionStateStore : SessionStateStoreProviderBase  
    {  
        private SessionStateSection pConfig;  
        private string pApplicationName;  
 
        public override void Initialize(string name, System.Collections.Specialized.NameValueCollection config)  
        {  
            base.Initialize(name, config);  
 
            pApplicationName =System.Web.Hosting.HostingEnvironment.ApplicationVirtualPath;  
            System.Configuration.Configuration cfg = WebConfigurationManager.OpenWebConfiguration(pApplicationName);  
            pConfig =(SessionStateSection)cfg.GetSection("system.web/sessionState");  
        }  
 
        public override SessionStateStoreData CreateNewStoreData(System.Web.HttpContext context, int timeout)  
        {  
            return new SessionStateStoreData(new SessionStateItemCollection(), SessionStateUtility.GetSessionStaticObjects(context), timeout);  
        }  
 
        public override void CreateUninitializedItem(System.Web.HttpContext context, string id, int timeout)  
        {  
            //insert to db  
            MongoDBSessionEntity session = new MongoDBSessionEntity();  
            session.ApplicationName = this.pApplicationName;  
            session.SessionId = id;  
            session.Created = DateTime.Now;  
            session.Expires = DateTime.Now.AddMinutes(pConfig.Timeout.Minutes);  
            session.LockDate = DateTime.Now;  
            session.LockId = 0;  
            session.Timeout = timeout;  
            session.Locked = false;  
            session.Flags = (int)SessionStateActions.InitializeItem;  
 
            MongoCollection<MongoDBSessionEntity> collection = Helper.GetMongoDBCollection(id);  
            collection.Save(session);  
        }  
 
        public override void Dispose()  
        {  
        }  
 
        public override void EndRequest(System.Web.HttpContext context)  
        {  
        }  
 
        public override SessionStateStoreData GetItem(System.Web.HttpContext context, string id, out bool locked, out TimeSpan lockAge, out object lockId, out SessionStateActions actions)  
        {  
            return GetSessionStoreItem(false, context, id, out locked, out lockAge, out lockId, out actions);  
        }  
 
        public override SessionStateStoreData GetItemExclusive(System.Web.HttpContext context, string id, out bool locked, out TimeSpan lockAge, out object lockId, out SessionStateActions actions)  
        {  
            return GetSessionStoreItem(true, context, id, out locked, out lockAge, out lockId, out actions);  
        }  
 
        public override void InitializeRequest(System.Web.HttpContext context)  
        {  
        }  
 
        public override void ReleaseItemExclusive(System.Web.HttpContext context, string id, object lockId)  
        {  
            //update locked=0, expired=, where lockId=?  
            MongoCollection<MongoDBSessionEntity> collection = Helper.GetMongoDBCollection(id);  
 
            var query = Query.And(  Query.EQ("LockId", int.Parse(lockId.ToString())),  
                                    Query.EQ("_id", id),   
                                    Query.EQ("ApplicationName", pApplicationName));  
            var update = Update.Set("Locked", false)  
                                .Set("Expires", DateTime.Now.AddMinutes(pConfig.Timeout.Minutes));  
 
            collection.Update(query, update);  
        }  
 
        public override void RemoveItem(System.Web.HttpContext context, string id, object lockId, SessionStateStoreData item)  
        {  
            //delete where sessionId=? and lockId=? and applicationname=?  
            MongoCollection<MongoDBSessionEntity> collection = Helper.GetMongoDBCollection(id);  
 
            var query = Query.And(Query.EQ("LockId", int.Parse(lockId.ToString())),  
                                    Query.EQ("_id", id),  
                                    Query.EQ("ApplicationName", pApplicationName));  
            collection.Remove(query);  
        }  
 
        public override void ResetItemTimeout(System.Web.HttpContext context, string id)  
        {  
            //update expire date  
            MongoCollection<MongoDBSessionEntity> collection = Helper.GetMongoDBCollection(id);  
 
            var query = Query.And(Query.EQ("_id", id),  
                                    Query.EQ("ApplicationName", pApplicationName));  
            var update = Update.Set("Expires", DateTime.Now.AddMinutes(pConfig.Timeout.Minutes));  
            collection.Update(query, update);  
        }  
 
        public override void SetAndReleaseItemExclusive(System.Web.HttpContext context, string id, SessionStateStoreData item, object lockId, bool newItem)  
        {  
            MongoCollection<MongoDBSessionEntity> collection = Helper.GetMongoDBCollection(id);  
            if (newItem)  
            {  
                //delete expired items  
                var query = Query.And(Query.EQ("_id", id),  
                                    Query.EQ("ApplicationName", pApplicationName),  
                                    Query.LT("Expires", DateTime.Now));  
 
                collection.Remove(query);  
 
                //insert new item  
                MongoDBSessionEntity session = new MongoDBSessionEntity();  
                session.ApplicationName = this.pApplicationName;  
                session.SessionId = id;  
                session.Created = DateTime.Now;  
                session.Expires = DateTime.Now.AddMinutes(pConfig.Timeout.Minutes);  
                session.LockDate = DateTime.Now;  
                session.LockId = 0;  
                session.Timeout = item.Timeout;  
                session.Locked = false;  
                session.Flags = (int)SessionStateActions.None;  
                session.SessionItems = Helper.Serialize((SessionStateItemCollection)item.Items);  
 
                collection.Save(session);  
            }  
            else 
            {  
                //update item  
                var query = Query.And(Query.EQ("_id", id),  
                                    Query.EQ("ApplicationName", pApplicationName),  
                                    Query.EQ("LockId", int.Parse(lockId.ToString())));  
                MongoDBSessionEntity entity= collection.FindOne(query);  
                entity.Expires = DateTime.Now.AddMinutes(item.Timeout);  
                entity.SessionItems = Helper.Serialize((SessionStateItemCollection)item.Items);  
                entity.Locked = false;  
                collection.Save(entity);  
            }  
        }  
 
        public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback)  
        {  
            return false;  
        }  
 
 
 
 
 
 
 
 
 
 
        private SessionStateStoreData GetSessionStoreItem(bool lockRecord, System.Web.HttpContext context,   
                                                            string id,  
                                                            out bool locked,  
                                                            out TimeSpan lockAge,  
                                                            out object lockId,  
                                                            out SessionStateActions actions)  
        {  
            SessionStateStoreData item = null;    
            lockAge = TimeSpan.Zero;  
            lockId = null;  
            locked = false;  
            actions = 0;  
 
            bool foundRecord = false;  
            bool deleteData = false;  
 
            MongoCollection<MongoDBSessionEntity> collection = Helper.GetMongoDBCollection(id);  
 
            if (lockRecord)  
            {   
                //update db, set locked=1, lockdate=now  
                var query1 = Query.And(Query.EQ("_id", id),  
                                    Query.EQ("ApplicationName", pApplicationName),  
                                    Query.EQ("Locked", MongoDB.Bson.BsonValue.Create(false)),  
                                    Query.GT("Expires", DateTime.UtcNow));  
 
                long count = collection.Find(query1).Count();  
                if (count == 0)  
                {  
                    locked = true;  
                }  
                else 
                {  
                    var update = Update.Set("Locked", true).Set("LockDate", DateTime.Now);  
                    collection.Update(query1, update);  
                    locked = false;  
                }  
            }  
            //get item by id  
            var query2 = Query.And(Query.EQ("_id", id),  
                                    Query.EQ("ApplicationName", pApplicationName));  
            MongoDBSessionEntity entity=collection.FindOne(query2);  
            if (entity != null)  
            {  
                if (entity.Expires < DateTime.Now)  
                {  
                    locked = false;  
                    deleteData = true;  
                }  
                else 
                {  
                    foundRecord = true;  
                }  
            }  
 
            //delete item if session expired  
            if (deleteData)  
            {  
                var query3 = Query.And(Query.EQ("_id", id),  
                                    Query.EQ("ApplicationName", pApplicationName));  
                collection.Remove(query3);  
            }  
 
            if (!foundRecord)  
                locked = false;  
 
            if (foundRecord && !locked)  
            {  
                if (lockId == null)  
                    lockId = 0;  
                lockId = (int)lockId + 1;  
 
                var query4 = Query.And(Query.EQ("_id", id),  
                                    Query.EQ("ApplicationName", pApplicationName));  
                var update4 = Update.Set("LockId", (int)lockId)  
                                        .Set("Flags", (int)SessionStateActions.None);  
                collection.Update(query4, update4);  
 
                if (actions == SessionStateActions.InitializeItem)  
                    item = CreateNewStoreData(context, pConfig.Timeout.Minutes);  
                else 
                    item = Helper.Deserialize(context, entity.SessionItems, entity.Timeout);  
            }  
            return item;  
        }  
    }

由于很多方法會用到MongoCollection，因此寫了個static公用函數，如下：

public static MongoCollection<MongoDBSessionEntity> GetMongoDBCollection(string sessionId)  
        {  
            IPartitionResolver resolver = new MongoDBSessionPartitionResolver();  
            string mongoDbConnectionString = resolver.ResolvePartition(sessionId);  
 
            MongoClient client = new MongoClient(mongoDbConnectionString);  
            MongoServer srv = client.GetServer();  
            MongoDatabase db = srv.GetDatabase(SessionConfiguration.MongoDBName);  
            if (!db.CollectionExists(SessionConfiguration.MongoDBCollectionName))  
                db.CreateCollection(SessionConfiguration.MongoDBCollectionName);  
 
            MongoCollection<MongoDBSessionEntity> collection = db.GetCollection<MongoDBSessionEntity>(SessionConfiguration.MongoDBCollectionName);  
 
            return collection;  
        }