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說一說sateless的那些事~，一說sateless那些事

編輯：關於.NET

說一說sateless的那些事~，一說sateless那些事

前段時間工作需要生平第一次聽到“無狀態”一詞隨後了解了下怕自己忘記隨手記錄下來

尚未創建過Session:
InitializeRequest -> CreateNewStoreData

InitializeRequest -> ResetItemTimeout -> InitializeRequest -> GetItemExclusive
（一種假象：http://localhost:29566和http://localhost:29566/Default.aspx）

已經創建過Session:

InitializeRequest -> GetItemExclusive
但如果沒查到會 CreateUninitializedItem -> GetItemExclusive（不管經過是什麼，都會進入Page_Load）

--------------Page_load--------------
EndRequest（尚未創建過Session）
ReleaseItemExclusive -> EndRequest（已經創建過Session，此次無Update）
SetAndReleaseItemExclusive -> EndRequest （已經創建過Session，且此次有Update）

HttpModule -> RedisSession（InitializeRequest -> ResetItemTimeout只會在進入HttpHandle前調用這兩個方法） -> HttpHandle
不要再HttpModule、HttpHandle中操作Session
HttpModel是因為調用順序問題，HttpHandle是因為就算更新了，也不會進行被同步到Redis
好吧，其實這兩個的context.Session 都是null

Media資源（圖片、css、script）是不會進來的

SessionStateStoreProviderBase類

定義一個數據存儲會話狀態所需的成員

Namespace: System.Web.SessionState
Assembly: System.Web (in System.Web.dll)

1.初始化每個請求對象

public abstract void InitializeRequest(HttpContext context)

Redis:

/// <summary>
        /// 在異步回發初始化期間提出
        /// </summary>
        /// <param name="context"></param>
        public override void InitializeRequest(HttpContext context)
        {
            if (context != null && context.Request != null)
            {
                LogInfoFormat("InitializeRequest invoking: Cookie.ASP.NET_SessionId:{0},RequestRawUrl:{1}"
                    , context.Request.Cookies != null && context.Request.Cookies["ASP.NET_SessionId"] != null ? context.Request.Cookies["ASP.NET_SessionId"].Value : ""
                    , context.Request.RawUrl
                    );
            }
        }

2.創建一個新的對象用對當前的請求

public abstract SessionStateStoreData CreateNewStoreData(HttpContext context,int timeout)


Redis:

　public override SessionStateStoreData CreateNewStoreData(HttpContext context, int timeout)
　{
　　　return new SessionStateStoreData(new SessionStateItemCollection(),staticObjectsGetter(context),timeout);
　}

3.更新此次會話的過期時間

public abstract void ResetItemTimeout(HttpContext context,string id)

Redis：

        public override void ResetItemTimeout(HttpContext context, string id)
        {
            //throw new NotImplementedException();
        }

4.從會話狀態存儲中返回只讀會話狀態

public abstract SessionStateStoreData GetItemExclusive(HttpContext context,string id,out bool locked,out TimeSpan lockAge,out object lockId,out SessionStateActions actions)

Redis：

public override SessionStateStoreData GetItemExclusive(HttpContext context, string id, out bool locked, out TimeSpan lockAge, out object lockId, out SessionStateActions actions)
        {
            LogInfoFormat("GetItemExclusive invoking: id:{0},RequestRawUrl:{1}"
                , id
                , context != null && context.Request != null ? context.Request.RawUrl : ""
                );
            //讀取redis,從redis獲取session
            return GetItemFromSessionStore(true, context, id, out locked, out lockAge, out lockId, out actions);
        }

/// <summary>
/// 從Redis讀取
/// </summary>
/// <param name="isWriteLockRequired"></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>
private SessionStateStoreData GetItemFromSessionStore(bool isWriteLockRequired, HttpContext context, string id, out bool locked, out TimeSpan lockAge, out object lockId, out SessionStateActions actions)
{
　　locked = false;
　　lockAge = TimeSpan.Zero;
　　lockId = null;
　　actions = SessionStateActions.None;
　　SessionStateStoreData result = null;

　　var key = GetSessionIdKey(id);

　　var stateRaw = RedisHelper.RedisDB.HashGetAll(key);

　　RedisSessionState state;
　　if (!RedisSessionState.TryParse(stateRaw, out state))
　　{
　　　　locked = false; //如果在數據存儲區中未找到會話項數據，GetItemExclusive 方法就會將 locked out 參數設置為 false 並返回 null
　　　　return null; //CreateUninitializedItem -> GetItemExclusive
　　}

　　actions = state.Flags;

　　if (state.Locked)
　　{
　　　　locked = true; //如果在數據存儲區中找到會話項數據但是數據被鎖定，GetItemExclusive 方法就會將 locked out 參數設置為 true，將 lockAge out 參數設置為當前日期和時間與項被鎖定時的日期和時間（從數據存儲區中檢索）的差值，將 lockId out 參數設置為從數據存儲區中檢索的鎖定標識符，並返回 null
　　　　lockId = state.LockId;
　　　　//lockAge = new TimeSpan((DateTime.UtcNow - state.LockDate).Ticks * 7);//ExecutionTimeout有點長，100s左右
　　　　lockAge = DateTime.UtcNow - state.LockDate;
　　　　return null;
　　}

　　if (isWriteLockRequired)
　　{
　　　　locked = state.Locked = true;
　　　　state.LockDate = DateTime.UtcNow;
　　　　lockAge = TimeSpan.Zero;
　　　　lockId = ++state.LockId;
　　}

　　state.Flags = SessionStateActions.None;

　　UpdateSessionState(key, state);

　　var items = actions == SessionStateActions.InitializeItem ? new SessionStateItemCollection() : state.Items;

　　result = new SessionStateStoreData(items, staticObjectsGetter(context), state.Timeout);

　　return result;
}

5.添加一個新的會話狀態項到會話存儲裡

public abstract void CreateUninitializedItem(HttpContext context,string id,int timeout)

Redis：

// GetItemExclusive如果沒有查到，則會調用該方法（非因為Locked return null） 
public override void CreateUninitializedItem(HttpContext context, string id, int timeout)
        {
            var key = GetSessionIdKey(id);

            var state = new RedisSessionState()
            {
                Timeout = timeout,
                Flags = SessionStateActions.InitializeItem
            };

            UpdateSessionState(key, state);
        }
 private void UpdateSessionState(string key, RedisSessionState state)
　　{
　　　　UseTransaction(transaction =>
　　　　{
　　　　　　transaction.HashSetAsync(key, state.ToHashEntryArr());
　　　　　　transaction.KeyExpireAsync(key, TimeSpan.FromMinutes(state.Timeout));
　　　　});
　　}

6.一個請求結束後回傳

public abstract void EndRequest(HttpContext context)

Redis：

        public override void EndRequest(HttpContext context)
        {
            //throw new NotImplementedException();
        }

7.釋放會話狀態存儲中的鎖定

public abstract void ReleaseItemExclusive(HttpContext context,string id,object lockId)

Redis：

///1、一次Http請求處理完之後（在Page_Load 及 aspx之後），如果沒有發生了Session Update，則會調用此方法
///2、Page_Load之前，如果反復執行GetItemExclusive始終是locked狀態，一段時間之後系統會自行調用此方法來嘗試釋放.
///   如果 SessionStateModule 對象在調用 GetItemExclusive 或 GetItem 方法期間遇到鎖定的會話數據，它將以半秒為間隔重新請求會話數據，
///   直到鎖定被釋放或者會話數據的鎖定時間超過 ExecutionTimeout 屬性的值。如果超過了執行超時時間，SessionStateModule 對象將調用 ReleaseItemExclusive 方法以釋放會話存儲區數據並隨即請求會話存儲區數據
public override void ReleaseItemExclusive(HttpContext context, string id, object lockId)
        {
            UnlockSessionStateIfLocked(id, (int)lockId);
        }
　　　　 /// <summary>
        /// 釋放會話存儲區數據並隨即請求會話存儲區數據
        /// </summary>
        /// <param name="id"></param>
        /// <param name="lockId"></param>
        private void UnlockSessionStateIfLocked(string id, int lockId)
        {
            var key = GetSessionIdKey(id);

            var stateRaw = RedisHelper.RedisDB.HashGetAll(key);

            RedisSessionState state;

            if (RedisSessionState.TryParse(stateRaw, out state) && state.Locked && state.LockId == lockId)
            {
                UnlockSessionState(key, state.Timeout);
            }
        }

        /// <summary>
        /// 不知道這樣 對比 UpdateSessionState， 性能怎麼樣。這裡雖然分成多項，但會作為一個transaction提交
        /// </summary>
        /// <param name="client"></param>
        /// <param name="key"></param>
        /// <param name="state"></param>
        private void UnlockSessionState(string key, int timeout)
        {
            UseTransaction(transaction =>
            {
                transaction.HashSetAsync(key, "locked", false);
                transaction.HashSetAsync(key, "lockId", 0);
                transaction.HashSetAsync(key, "lockDate", 0);
                //transaction.HashSetAsync(key, "timeout", timeout);    //沒必要
                transaction.KeyExpireAsync(key, TimeSpan.FromMinutes(timeout));
            });
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="action"></param>
        private void UseTransaction(Action<ITransaction> action)
        {
            try
            {
                //Redis的更新 都會進這
                var transaction = RedisHelper.RedisDB.CreateTransaction();
                action(transaction);
                transaction.Execute();
            }
            catch (Exception ex)
            {
                LogError(ex.Message, ex);
            }
        }

8.在更新會話狀態數據存儲與當前請求的值的會話項信息，並清除對數據的鎖定

public abstract void SetAndReleaseItemExclusive(HttpContext context,string id,SessionStateStoreData item,object lockId,bool newItem)

Redis:

/// 一次Http請求處理完之後（在Page_Load 及 aspx之後），如果發生了Session Update，則會調用此方法
public override void SetAndReleaseItemExclusive(HttpContext context, string id, SessionStateStoreData item, object lockId, bool newItem)
        {
            if (newItem)  //true:定義一個新的狀態
            {
                var state = new RedisSessionState()
                {
                    Items = (SessionStateItemCollection)item.Items,
                    Timeout = item.Timeout,
                };

                var key = GetSessionIdKey(id);
                UpdateSessionState(key, state);
            }
            else //false 已存在的狀態
            {
                UpdateSessionStateIfLocked(id, (int)lockId, state =>
                {
                    state.Items = (SessionStateItemCollection)item.Items;
                    state.Locked = false;
                    state.Timeout = item.Timeout;
                });
            }

        }

　　　　 /// <summary>
        /// 
        /// </summary>
        /// <param name="id"></param>
        /// <param name="lockId"></param>
        /// <param name="stateAction"></param>
        private void UpdateSessionStateIfLocked(string id, int lockId, Action<RedisSessionState> stateAction)
        {
            var key = GetSessionIdKey(id);

            var stateRaw = RedisHelper.RedisDB.HashGetAll(key);

            RedisSessionState state;

            if (RedisSessionState.TryParse(stateRaw, out state) && state.Locked && state.LockId == lockId)
            {
                stateAction(state);
                UpdateSessionState(key, state);
            }

        }

  　　　 /// <summary>
        /// 
        /// </summary>
        /// <param name="client"></param>
        /// <param name="key"></param>
        /// <param name="state"></param>
        private void UpdateSessionState(string key, RedisSessionState state)
        {
            UseTransaction(transaction =>
            {
                transaction.HashSetAsync(key, state.ToHashEntryArr());
                transaction.KeyExpireAsync(key, TimeSpan.FromMinutes(state.Timeout));
            });
        }
  　　　 /// <summary>
        /// 
        /// </summary>
        /// <param name="action"></param>
        private void UseTransaction(Action<ITransaction> action)
        {
            try
            {
                //Redis的更新 都會進這
                var transaction = RedisHelper.RedisDB.CreateTransaction();
                action(transaction);
                transaction.Execute();
            }
            catch (Exception ex)
            {
                LogError(ex.Message, ex);
            }
        }

未完，待續...