问题如下：

针对.net core 异常奇怪问题分析

• cpu 和内存不高，但是线上系统运行很卡
• cpu使用率瞬时升高，甚至突破100%（负载突然升高）
• 其它服务(或者进程外的资源)传入负载能力超出（或提示连接超时）,比如提示（StackExchange.Redis.RedisConnectionException: It was not possible to connect to the redis server(s); to create a disconnected multiplexer, disable AbortOnConnectFail. Timeout at StackExchange.Redis.ConnectionMultiplexer.ConnectImpl(Func`1 multiplexerFactory, TextWriter log)）
• 也可能是一次显示为"较长"的数据库查询
• 或者任何非cpu活动（如任何I/O或延迟），因此似乎非常I/O 操作随机需要的时间比它应该需要的时间长
• 线程数莫名奇妙的不断升高

1、StackExchange.Redis.RedisConnectionException: It was not possible to connect to the redis server(s); to create a disconnected multiplexer, disable AbortOnConnectFail. Timeout
at StackExchange.Redis.ConnectionMultiplexer.ConnectImpl(Func`1 multiplexerFactory, TextWriter log)

2、There is already an open DataReader associated with this Command which must be closed first

3、A second operation started on this context before a previous operation completed. This is usually caused by different threads using the same instance of DbContext, however instance members are not guaranteed to be

static void Main(string[] args)
        {
          //按键后开始执行
            Console.ReadKey();
            //模拟并发
            while (true)
            {
                Task.Run(Producer);
                Thread.Sleep(200);
            }
           
        }
        /// <summary>
        /// 如果处理程序耗时>请求耗时，也就是说引起并发，就会导致死锁
        /// </summary>
        static void Producer()
        {
            var result = Process().Result;
            //或者
            //Process().Wait();
        }


        static async Task<bool> Process()
        {
            Console.WriteLine("Start - " + DateTime.Now.ToLongTimeString());
            await Task.Run(() =>
            {
                //模拟任务执行耗时
                Thread.Sleep(1000);
            });

            Console.WriteLine("Ended - " + DateTime.Now.ToLongTimeString());
            return true;
        }        

 　　　　static async Task Producer()
        {
            await Process();
        }