可灵活扩展的自定义Session状态存储驱动

Session是互联网应用中非常重要的玩意儿，对于超过单台部署的站点集群，都会存在会话共享的需求。在web.config中，微软提供了sessionstate节点来定义不同的Session状态存储方式。本文就自定义模式下的Session状态存储驱动提供一些干货。

首先，想要接管Session状态存储，需要了解一些基本的东西。

SessionIDManager

/// <summary>
/// 自定义SessionID管理器
/// </summary>
public class CustomSessionIDManager : SessionIDManager
{
/// <summary>
/// 创建SessionID
/// </summary>
/// <param name="context"></param>
/// <returns></returns>
public override string CreateSessionID(HttpContext context)
{
return string.Format("{0}.{1}",  SessionProviderConfigurationSectionHandler.SessionProviderSettings.SessionProfix, base.CreateSessionID(context));
}

/// <summary>
/// 验证
/// </summary>
/// <param name="id"></param>
/// <returns></returns>
public override bool Validate(string id)
{
string prefix = string.Empty;
string realId = string.Empty;

if (string.IsNullOrEmpty(id) || id.Trim().Length == 0)
{
return false;
}
var parsedValues = id.Split('.');
if (parsedValues == null || parsedValues.Length != 2)
{
return false;
}

prefix = parsedValues[0];
realId = parsedValues[1];

return base.Validate(realId);
}

}

想要共享Session，肯定就会有SessionID的前缀需求，而SessionIDManager就提供了可自定义的虚方法，这边以CustomSessionIDManager举例。CreateSessionID方法提供了创建SessionID的实现，重载该方法，用{0}.{1}的方式提供基于前缀的SessionID生成。而Validate是拆解带前缀的SessionID来验证真实的SessionID。

SessionStateStoreProviderBase

/// <summary>
/// 自定义Session状态存储驱动
/// </summary>
public sealed class CustomSessionStateStoreProvider : SessionStateStoreProviderBase
{

/// <summary>
/// 构造函数
/// </summary>
public CustomSessionStateStoreProvider()
{
sessionStateStoreBehavior = SessionProviderBehaviorFactory.CreateSessionStateStoreBehaviorInstance();
}

/// <summary>
/// Session状态存储行为
/// </summary>
readonly ISessionStateStoreBehavior sessionStateStoreBehavior;

/// <summary>
/// 创建新的存储数据
/// </summary>
/// <param name="context"></param>
/// <param name="timeout"></param>
/// <returns></returns>
public override SessionStateStoreData CreateNewStoreData(System.Web.HttpContext context, int timeout)
{
return new SessionStateStoreData(new SessionStateItemCollection(), SessionStateUtility.GetSessionStaticObjects(context), timeout);
}

/// <summary>
/// 创建未初始化的项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="timeout"></param>
public override void CreateUninitializedItem(System.Web.HttpContext context, string id, int timeout)
{
sessionStateStoreBehavior.CreateUninitializedItem(context, id, timeout);
}

/// <summary>
/// 获取项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="locked"></param>
/// <param name="lockAge"></param>
/// <param name="lockId"></param>
/// <param name="actions"></param>
/// <returns></returns>
public override SessionStateStoreData GetItem(System.Web.HttpContext context, string id, out bool locked, out TimeSpan lockAge, out object lockId, out SessionStateActions actions)
{
return sessionStateStoreBehavior.GetItem(false, context, id, out locked, out lockAge, out lockId, out actions);
}

/// <summary>
/// 独占获取项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="locked"></param>
/// <param name="lockAge"></param>
/// <param name="lockId"></param>
/// <param name="actions"></param>
/// <returns></returns>
public override SessionStateStoreData GetItemExclusive(System.Web.HttpContext context, string id, out bool locked, out TimeSpan lockAge, out object lockId, out SessionStateActions actions)
{
return sessionStateStoreBehavior.GetItem(true, context, id, out locked, out lockAge, out lockId, out actions);
}

/// <summary>
/// 独占释放项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="lockId"></param>
public override void ReleaseItemExclusive(System.Web.HttpContext context, string id, object lockId)
{
sessionStateStoreBehavior.ReleaseItem(context, id, lockId);
}

/// <summary>
/// 移除项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="lockId"></param>
/// <param name="item"></param>
public override void RemoveItem(System.Web.HttpContext context, string id, object lockId, SessionStateStoreData item)
{
sessionStateStoreBehavior.RemoveItem(context, id, lockId);
}

/// <summary>
/// 重设项的超时时间
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
public override void ResetItemTimeout(System.Web.HttpContext context, string id)
{
sessionStateStoreBehavior.ResetItemTimeout(context, id);
}

/// <summary>
/// 独占设置并释放项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="item"></param>
/// <param name="lockId"></param>
/// <param name="newItem"></param>
public override void SetAndReleaseItemExclusive(System.Web.HttpContext context, string id, SessionStateStoreData item, object lockId, bool newItem)
{
sessionStateStoreBehavior.SetAndReleaseItem(context, id, item, lockId, newItem);
}

/// <summary>
/// 回收
/// </summary>
public override void Dispose() { }

/// <summary>
/// 结束请求
/// </summary>
/// <param name="context"></param>
public override void EndRequest(System.Web.HttpContext context) { }

/// <summary>
/// 初始化请求
/// </summary>
/// <param name="context"></param>
public override void InitializeRequest(System.Web.HttpContext context) { }

/// <summary>
/// 设置项过期回掉
/// </summary>
/// <param name="expireCallback"></param>
/// <returns></returns>
public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback) { return false; }
}

SessionStateStoreProviderBase是提供Session状态存储驱动的基类。从基类分析，想要灵活扩展，核心就是对Session存储的那些方法实现进行抽象，让驱动在执行方法的时候不关心实现由谁来提供。因此，写一个SessionStateStoreBehavior接口，在CustomSessionStateStoreProvider的构造函数中，通过工厂在运行时得到实例。

SessionStateStoreBehavior

/// <summary>
/// Session状态存储行为接口
/// </summary>
public interface ISessionStateStoreBehavior
{
/// <summary>
/// 创建未初始化的项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="timeout"></param>
void CreateUninitializedItem(System.Web.HttpContext context, string id, int timeout);

/// <summary>
/// 获取项
/// </summary>
/// <param name="lockRecord"></param>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="locked"></param>
/// <param name="lockAge"></param>
/// <param name="lockId"></param>
/// <param name="actions"></param>
/// <returns></returns>
SessionStateStoreData GetItem(bool lockRecord, System.Web.HttpContext context, string id, out bool locked, out TimeSpan lockAge, out object lockId, out SessionStateActions actions);

/// <summary>
/// 释放项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="lockId"></param>
void ReleaseItem(System.Web.HttpContext context, string id, object lockId);

/// <summary>
/// 移除项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="lockId"></param>
void RemoveItem(System.Web.HttpContext context, string id, object lockId);

/// <summary>
/// 重设项的超时时间
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
void ResetItemTimeout(System.Web.HttpContext context, string id);

/// <summary>
/// 设置并释放项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="item"></param>
/// <param name="lockId"></param>
/// <param name="newItem"></param>
void SetAndReleaseItem(System.Web.HttpContext context, string id, SessionStateStoreData item, object lockId, bool newItem);
}

创建一个ISessionStateStoreBehavior，将涉及Session存储的方法公开。

/// <summary>
/// Session驱动行为工厂
/// </summary>
class SessionProviderBehaviorFactory
{
/// <summary>
/// 当前Session状态存储行为实例
/// </summary>
static ISessionStateStoreBehavior currentSessionStateStoreBehavior;

/// <summary>
/// 创建Session状态存储行为实例
/// </summary>
/// <returns></returns>
public static ISessionStateStoreBehavior CreateSessionStateStoreBehaviorInstance()
{
if (currentSessionStateStoreBehavior == null)
{
var types = Assembly.GetExecutingAssembly().GetTypes().Where(t => !t.IsAbstract && t.GetInterface(typeof(ISessionStateStoreBehavior).Name) != null);
var currentType = types.FirstOrDefault(t => t.Name == string.Format("{0}SessionStateStoreBehavior", SessionProviderConfigurationSectionHandler.SessionProviderSettings.SessionStateStoreProviderBehaviorName));
if (currentType != null)
{
currentSessionStateStoreBehavior = (ISessionStateStoreBehavior)Activator.CreateInstance(currentType);
}
}

return currentSessionStateStoreBehavior;
}
}

通过工厂得到当前应用程序域下的继承了ISessionStateStoreBehavior接口的所有实现类，并读取配置得到当前实例。

基于MongoDB的一个行为实现

/// <summary>
/// 基于Mongo的Session状态存储行为
/// </summary>
public class MongoSessionStateStoreBehavior : SessionStateStoreBehaviorBase, ISessionStateStoreBehavior
{
/// <summary>
/// 构造函数
/// </summary>
public MongoSessionStateStoreBehavior()
: base()
{
if (collection == null)
{
collection = GetMongoDBCollection();
var expiresKey = IndexKeys.Ascending("Expires");
var options = IndexOptions.SetTimeToLive(base.SessionStateSection.Timeout);
collection.EnsureIndex(expiresKey, options);
collection.EnsureIndex("LockId", "Locked");
}
}

static MongoCollection<MongoDBSessionDo> collection;

/// <summary>
/// 获取Mongo集合
/// </summary>
/// <returns></returns>
static MongoCollection<MongoDBSessionDo> GetMongoDBCollection()
{
var url = new MongoUrl(SessionProviderConfigurationSectionHandler.SessionProviderSettings.StorageConnectionString);
var client = new MongoClient(url);
var database = client.GetServer().GetDatabase(url.DatabaseName, WriteConcern.Unacknowledged);
return database.GetCollection<MongoDBSessionDo>(ConfigSection.SessionProviderConfigurationSectionHandler.SessionProviderSettings.SessionProfix);
}

/// <summary>
/// 创建未初始化项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="timeout"></param>
public void CreateUninitializedItem(System.Web.HttpContext context, string id, int timeout)
{
var session = new MongoDBSessionDo()
{
SessionId = id,
Created = DateTime.Now,
Expires = DateTime.Now.AddMinutes(base.SessionStateSection.Timeout.TotalMinutes),
LockDate = DateTime.Now,
LockId = 0,
Timeout = timeout,
Locked = false,
Flags = (int)SessionStateActions.InitializeItem,
};
collection.Save(session);
SetSessionIdCookieExpires(context, session.Expires);
}

/// <summary>
/// 获取项
/// </summary>
/// <param name="lockRecord"></param>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="locked"></param>
/// <param name="lockAge"></param>
/// <param name="lockId"></param>
/// <param name="actions"></param>
/// <returns></returns>
public System.Web.SessionState.SessionStateStoreData GetItem(bool lockRecord, System.Web.HttpContext context, string id, out bool locked, out TimeSpan lockAge, out object lockId, out System.Web.SessionState.SessionStateActions actions)
{
var item = default(SessionStateStoreData);
lockAge = TimeSpan.Zero;
lockId = null;
locked = false;
actions = 0;

bool foundRecord = false;
bool deleteData = false;

var session = collection.AsQueryable().FirstOrDefault(s => s.SessionId == id);

if (lockRecord)
{
locked = session != null && !session.Locked && session.Expires > DateTime.Now;
}

if (session != null)
{
if (session.Expires < DateTime.Now)
{
locked = false;
deleteData = true;
}
else
{
foundRecord = true;
}
}

if (deleteData)
{
collection.Remove(Query.EQ("_id", id));
}

if (!foundRecord)
locked = false;

if (foundRecord && !locked)
{
lockId = lockId == null ? 0 : (int)lockId + 1;
collection.Update(Query.EQ("_id", id), Update.Set("LockId", (int)lockId).Set("Flags", (int)SessionStateActions.None));
var timeout = actions == SessionStateActions.InitializeItem ? (int)base.SessionStateSection.Timeout.TotalMinutes : session.Timeout;
var sessionStateItemCollection = actions == SessionStateActions.InitializeItem ? new SessionStateItemCollection() : Helper.Deserialize(session.SessionItems);
item = new SessionStateStoreData(sessionStateItemCollection, SessionStateUtility.GetSessionStaticObjects(context), timeout);
}

return item;
}

/// <summary>
/// 释放项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="lockId"></param>
public void ReleaseItem(System.Web.HttpContext context, string id, object lockId)
{
var expires = DateTime.Now.AddMinutes(base.SessionStateSection.Timeout.TotalMinutes);
collection.Update(Query.And(Query.EQ("LockId", int.Parse(lockId.ToString())), Query.EQ("_id", id)), Update.Set("Locked", false).Set("Expires", expires));
SetSessionIdCookieExpires(context, expires);
}

/// <summary>
/// 移除项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="lockId"></param>
public void RemoveItem(System.Web.HttpContext context, string id, object lockId)
{
collection.Remove(Query.And(Query.EQ("LockId", int.Parse(lockId.ToString())), Query.EQ("_id", id)));
SetSessionIdCookieExpires(context, DateTime.Now.AddDays(-1), true);
}

/// <summary>
/// 重设项超时时间
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
public void ResetItemTimeout(System.Web.HttpContext context, string id)
{
var expires = DateTime.Now.AddMinutes(base.SessionStateSection.Timeout.TotalMinutes);
collection.Update(Query.And(Query.EQ("_id", id)), Update.Set("Expires", expires));
SetSessionIdCookieExpires(context, expires);
}

/// <summary>
/// 设置并释放项
/// </summary>
/// <param name="context"></param>
/// <param name="id"></param>
/// <param name="item"></param>
/// <param name="lockId"></param>
/// <param name="newItem"></param>
public void SetAndReleaseItem(System.Web.HttpContext context, string id, System.Web.SessionState.SessionStateStoreData item, object lockId, bool newItem)
{
var session = default(MongoDBSessionDo);
if (newItem)
{
session = new MongoDBSessionDo();
session.SessionId = id;
session.Created = DateTime.Now;
session.Expires = DateTime.Now.AddMinutes(base.SessionStateSection.Timeout.TotalMinutes);
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);
}
else
{
session = collection.FindOne(Query.And(Query.EQ("_id", id), Query.EQ("LockId", int.Parse(lockId.ToString()))));
session.Expires = DateTime.Now.AddMinutes(item.Timeout);
session.SessionItems = Helper.Serialize((SessionStateItemCollection)item.Items);
session.Locked = false;
}
collection.Save(session);
SetSessionIdCookieExpires(context, session.Expires);
}
}

配置相关

<configSections>
<section name="SessionProviderSettings" type="CustomSessionDemo.SessionProviderConfigurationSectionHandler, CustomSessionDemo"/>
</configSections>

<SessionProviderSettings>
<SessionProfix>Test</SessionProfix>
<IsSynchronousSessionIdTimeout>true</IsSynchronousSessionIdTimeout>
<SessionStateStoreProviderBehaviorName>Mongo</SessionStateStoreProviderBehaviorName>
<StorageConnectionString>mongodb://192.168.1.43:27017/TestSessionDB</StorageConnectionString>
</SessionProviderSettings>

<system.web>
<sessionState mode="Custom" customProvider="SessionProvider" sessionIDManagerType="CustomSessionDemo.CustomSessionIDManager" timeout="20">
<providers>
<add name="SessionProvider" type="CustomSessionDemo.CustomSessionStateStoreProvider, CustomSessionDemo"/>
</providers>
</sessionState>

执行效果