Question

I am using the ServiceStack.Redis C# client to talk to Redis.

With few request everything is ok, but when I get LoadRunner to request it or use multi-threading to make requests, I get some errors that say I am using the wrong command.

I check the errors, and it seems that it cut off the command, or it mess up.

Here is my code, very simple. Has anyone come across this problem? The errors happen when I call the Push method using multi-threading.

public class ImpresstionQueueService : IQueueService<InsertImpressionRequest>
    {
        private string _queueName;
        private string _host;
        private static IRedisClient redisClient = new RedisClient(ConfigHost);
        private static string ConfigHost
        {
            get
            {
                return ConfigurationManager.AppSettings.Get("redis_host");
            }
        }
        private string Host
        {
            get
            {
                if (!string.IsNullOrEmpty(_host))
                    return _host;
                else
                {
                    return ConfigurationManager.AppSettings.Get("redis_host");
                }
            }
        }
        public ImpresstionQueueService(string queue_name)
        {
            this._queueName = queue_name;
        }

        public ImpresstionQueueService(string host, string queu_name)
        {
            this._queueName = queu_name;
            this._host = host;
        }

        #region IQueueService<InsertImpressionRequest> Members
        class testData
        {

        }
        public int Push(InsertImpressionRequest value)
        {
            try
            {
                //using (var redisClient = new RedisClient(this.Host))
                {
                    //ser
                    string ser_value = TypeSerializer.SerializeToString<InsertImpressionRequest>(value);
                    //push
                    redisClient.AddItemToList(this._queueName, ser_value);//here will be error

                }
            }
            catch (Exception ex)
            {
                HLogger.GetLogger("RedisLogger").Error(ex.Message + ex.StackTrace);
            }
            //throw new NotImplementedException();
            return 1;
        }

        public InsertImpressionRequest Pop()
        {
            InsertImpressionRequest request = null;
            //using (var redisClient = new RedisClient(this.Host))
            {
                string pop_string_value = redisClient.PopItemFromList(this._queueName);
                //deseri
                if (pop_string_value != null)
                {
                    request = TypeSerializer.DeserializeFromString<InsertImpressionRequest>(pop_string_value);
                }
            }
            return request;
        }

        #endregion
    }

Answer 1

You are probably using the same Redis connection simultaneously from multiple threads. Both threads could possibly send commands or wait for replies at the same time. When this happens, one thread receives data intended for the other thread. This causes your error.

If you use one Redis client per thread (instead of one client per ImpresstionQueueService), each thread can send commands at the same time without interfering with each other.

Alternatively, you can create a client just for the single request (which you commented out just above the error location). The disadvantage of this alternative is the overhead of a new connection every time (which might be large or small or unnoticeable).