使用StackExchange.Redis在C#中连接Azure Redis缓存超时问题

我正在将Azure Redis缓存（开发用Basic C0实例）集成到.Net 4.6.1系统中，使用StackExchange.Redis v2.6.90客户端库，运行环境均为Windows（本地Win10开发，测试用Server 2019 Std）。

编写的连接封装类 #

using System;
using System.Net;
using StackExchange.Redis;

namespace Rimes.Azure
{
    public class RedisCache
    {
        private ConnectionMultiplexer _redis;

        private void Initialize(ConfigurationOptions options)
        {
            // Azure requires TLS 1.2 but .Net uses TLS 1.1 by default
            ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

            _redis = ConnectionMultiplexer.Connect(options);
        }

        public RedisCache(string endPoint, string token, bool useSsl = true, bool abortOnConnectFail = true)
        {
            var options = ConfigurationOptions.Parse(endPoint);
            options.Password = token;
            options.Ssl = useSsl;
            options.AbortOnConnectFail = abortOnConnectFail;

            Initialize(options);
        }

        public string Get(string key)
        {
            IDatabase db = _redis.GetDatabase();
            return db.StringGet(key);
        }

        public bool Set(string key, string value, int timeToLive)
        {
            IDatabase db = _redis.GetDatabase();
            return db.StringSet(key, value, TimeSpan.FromSeconds(timeToLive));
        }
    }
}

问题现象 #

代码在本地开发机器上运行正常，但测试服务器上完全无法工作，实例化、获取、设置操作均触发RedisTimeoutException错误，错误日志如下：

Exception type: RedisTimeoutException 
Exception message: Timeout performing PSETEX (5000ms), inst: 0, qu: 1, qs: 0, aw: False, bw: SpinningDown, last-in: 0, cur-in: 0, sync-ops: 2, async-ops: 1, serverEndpoint: xxx.redis.cache.windows.net:6380, conn-sec: n/a, mc: 1/1/0, mgr: 10 of 10 available, clientName: xxx(SE.Redis-v2.6.90.64945), IOCP: (Busy=0,Free=1000,Min=12,Max=1000), WORKER: (Busy=2,Free=32765,Min=12,Max=32767), v: 2.6.90.64945
at StackExchange.Redis.ConnectionMultiplexer.ExecuteSyncImpl[T](Message message, ResultProcessor`1 processor, ServerEndPoint server, T defaultValue)
at Rimes.Azure.RedisCache.Set(String key, String value, TimeSpan expiry) 

已尝试的排查步骤 #

• 将超时时间从默认5000ms提升至30000ms - 无变化
• 使用psping验证与Azure的连接 - 连接成功
• 检查本地服务器及Azure防火墙设置 - Azure无防火墙配置，本地服务器允许出站连接
• 检查.Net版本 - 两者均运行.Net 4.8，仅本地版本为4.8.04084，服务器版本为4.8.03761
• 联系网络团队排查外部因素 - 未发现异常
• 使用Python redis 3.5.3库重新开发 - 两台机器均能正常连接缓存

更新记录 #

更新1：
测试服务器在2月14日（周五）可正常运行，2月17日（周一）失效。发现微软在14日发布了两个.Net安全更新KB5022504和KB5022782，但卸载后问题仍存在。进一步发现服务器仅接收安全更新，本地开发机仅接收功能更新。

更新2：
开启并使用Azure Redis的非SSL端口可正常工作，回退到TLS 1.0也可正常工作，但设置更高版本TLS则失败，附加日志如下：

11:09:02.9964: Allowing 1 endpoint(s) 00:00:05 to respond...
11:09:02.9964: Awaiting 1 available task completion(s) for 5000ms, IOCP: (Busy=0,Free=1000,Min=2,Max=1000), WORKER: (Busy=4,Free=32763,Min=10,Max=32767)
11:09:03.0241: Configuring TLS
11:09:03.0554: Connection failed: xxx.redis.cache.windows.net:6380 (Subscription, AuthenticationFailure): AuthenticationFailure on xxx.redis.cache.windows.net:6380/Subscription, Initializing/NotStarted, last: NONE, origin: ConnectedAsync, outstanding: 0, last-read: 0s ago, last-write: 0s ago, keep-alive: 60s, state: Connecting, mgr: 10 of 10 available, last-heartbeat: never, global: 0s ago, v: 2.6.96.30123
11:09:03.0554: > A call to SSPI failed, see inner exception.
11:09:03.0554: > The function requested is not supported
11:09:03.0554: xxx.redis.cache.windows.net:6380: OnConnectedAsync completed (Disconnected)
...
11:09:03.1178: Endpoint Summary:
11:09:03.1178:   xxx.redis.cache.windows.net:6380: Standalone v4.0.0, primary; keep-alive: 00:01:00; int: Disconnected; sub: Disconnected; not in use: DidNotRespond
11:09:03.1178:   xxx.redis.cache.windows.net:6380: int ops=0, qu=0, qs=0, qc=0, wr=0, socks=3; sub ops=0, qu=0, qs=0, qc=0, wr=0, socks=3
11:09:03.1178:   xxx.redis.cache.windows.net:6380: Circular op-count snapshot; int: 0 (0.00 ops/s; spans 10s); sub: 0 (0.00 ops/s; spans 10s)
11:09:03.1178: Sync timeouts: 0; async timeouts: 0; fire and forget: 0; last heartbeat: -1s ago
11:09:03.1178: Starting heartbeat...
11:09:08.1781: Encountered exception: StackExchange.Redis.RedisTimeoutException: The timeout was reached before the message could be written to the output buffer, and it was not sent, command=SUBSCRIBE, timeout: 5000, inst: 0, qu: 0, qs: 0, aw: False, bw: CheckingForTimeout, rs: NotStarted, ws: Initializing, in: 0, last-in: 0, cur-in: 0, sync-ops: 0, async-ops: 1, serverEndpoint: xxx.redis.cache.windows.net:6380, conn-sec: n/a, mc: 1/1/0, mgr: 10 of 10 available, clientName: LDOKTATEST01(SE.Redis-v2.6.96.30123), IOCP: (Busy=0,Free=1000,Min=2,Max=1000), WORKER: (Busy=6,Free=32761,Min=10,Max=32767), v: 2.6.96.30123
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebugge

基于配置TLS后的SSPI失败错误，移除了SecurityProtocol设置并通过注册表配置.Net使用TLS 1.2后问题解决。

当前需求 #

需要了解如何在代码中设置TLS 1.2版本，无需修改注册表即可正常工作。

内容的提问来源于stack exchange，提问作者Simon Pratt