RavenDB 在高负载下抛出 InvalidOperationException

我不知道为什么，但是当我对RavenDB进行并发写入负载测试时，在高负载下，我收到以下异常："集合已修改;枚举操作可能无法执行。

高负载，我说的是每秒 1000 个请求，更新 100 个文档。为了对此提供一些上下文，我将使用 RavenDB 在 MVC 站点上记录操作，并且我正在运行一个测试工具来调用 log 方法，以查看它是否可以处理记录这么多事情。每个文档表示用户在站点会话中的操作。

如果有帮助，则具有相同数量请求的较少文档运行良好。每秒请求数比例较高的文档较少也运行良好。

我从研究中发现，在线程之间共享 IDocumentSession 有时是负责任的，但我不相信我的代码会这样做。

下面是相关的日志记录逻辑：

public class ActivityLogger : IActivityLogger
{
    private static ActivityLogger _instance;
    public static ActivityLogger Instance
    {
        get
        {
            if (_instance == null)
            {
                _instance = new ActivityLogger();
            }
            return _instance;
        }
        set { _instance = value; }
    }
    private static DocumentStore docStoreInstance;
    // keeping this as a singleton - we only ever want one as it's expensive
    private static DocumentStore DocumentStore
    {
        get
        {
            if (docStoreInstance == null)
            {
                docStoreInstance = new DocumentStore() {ConnectionStringName = "RavenLogging"};
                docStoreInstance.Initialize();
            }
            return docStoreInstance;
        }
    }
    ...
    /// <summary>
    /// Logs the given LogItem to Raven, to the given UserSession
    /// </summary>
    public void Log(LogItem item, UserSession userSession)
    {
        if (userSession == null)
        {
            return;
        }
        if (!userSession.Activities.Contains(item))
        {
            userSession.Activities.Add(item);
            if (Cache != null)
                Cache.AddToSession(CachedObjects.USER_LOGGING_SESSION, userSession);
        }
        // done in a task since we don't want the app to wait for us to finish logging
        Task.Factory.StartNew(() =>
        {
            using (var session = DocumentStore.OpenSession())
            {
                try
                {
                    session.Store(userSession);
                    session.SaveChanges();
                }
                catch (Raven.Abstractions.Exceptions.ConcurrencyException ce)
                {
                    if (ce.ExpectedETag != ce.ActualETag)
                    {
                        // the user session is stale, reload it and try again
                        userSession = session.Load<UserSession>(userSession.Id);
                        Log(item, userSession);
                    }
                }
            }
        });
    }
}

这是我的测试工具中的代码

public void Begin()
{
    startTime = DateTime.Now;
    DateTime endTime = startTime.AddSeconds(Duration);
    int itemsLoggedThisSecond, secondsRemaining = 0;
    while (DateTime.Now < endTime)
    {
        // if we're still on the same second somehow, wait
        if (endTime.Subtract(DateTime.Now).Seconds == secondsRemaining)
        {
            Thread.Sleep(10);
            continue;
        }
        itemsLoggedThisSecond = 0;
        while (itemsLoggedThisSecond < RequestsPerSecond)
        {
            int innerItemsLoggedThisSecond = itemsLoggedThisSecond;
            Parallel.ForEach(Sessions, (session, state) =>
            {
                if (innerItemsLoggedThisSecond == RequestsPerSecond)
                {
                    state.Break();
                }
                var item = MakeRandomLogItem();
                ActivityLogger.Instance.Log(item, session);
                if (!session.Activities.Contains(item))
                {
                    session.Activities.Add(item);
                }
                innerItemsLoggedThisSecond++;
            });
            itemsLoggedThisSecond = innerItemsLoggedThisSecond;
        }
        secondsRemaining = (int) endTime.Subtract(DateTime.Now).TotalSeconds;
        Console.Write("'r" + secondsRemaining + " seconds remaining   ");
    }
}

如果它有帮助，这里是例外。

  System.InvalidOperationException was unhandled by user code
  HResult=-2146233079
  Message=Collection was modified; enumeration operation may not execute.
  Source=mscorlib
  StackTrace:
       at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
       at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
       at System.Collections.Generic.List`1.Enumerator.MoveNext()
       at Raven.Imports.Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList(JsonWriter writer, IWrappedCollection values, JsonArrayContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty) in c:'Builds'RavenDB-Stable'Imports'Newtonsoft.Json'Src'Newtonsoft.Json'Serialization'JsonSerializerInternalWriter.cs:line 524
       at Raven.Imports.Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty) in c:'Builds'RavenDB-Stable'Imports'Newtonsoft.Json'Src'Newtonsoft.Json'Serialization'JsonSerializerInternalWriter.cs:line 129
       at Raven.Imports.Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject(JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty) in c:'Builds'RavenDB-Stable'Imports'Newtonsoft.Json'Src'Newtonsoft.Json'Serialization'JsonSerializerInternalWriter.cs:line 383
       at Raven.Imports.Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty) in c:'Builds'RavenDB-Stable'Imports'Newtonsoft.Json'Src'Newtonsoft.Json'Serialization'JsonSerializerInternalWriter.cs:line 124
       at Raven.Imports.Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value) in c:'Builds'RavenDB-Stable'Imports'Newtonsoft.Json'Src'Newtonsoft.Json'Serialization'JsonSerializerInternalWriter.cs:line 62
       at Raven.Imports.Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value) in c:'Builds'RavenDB-Stable'Imports'Newtonsoft.Json'Src'Newtonsoft.Json'JsonSerializer.cs:line 627
       at Raven.Imports.Newtonsoft.Json.JsonSerializer.Serialize(JsonWriter jsonWriter, Object value) in c:'Builds'RavenDB-Stable'Imports'Newtonsoft.Json'Src'Newtonsoft.Json'JsonSerializer.cs:line 599
       at Raven.Json.Linq.RavenJToken.FromObjectInternal(Object o, JsonSerializer jsonSerializer) in c:'Builds'RavenDB-Stable'Raven.Abstractions'Json'Linq'RavenJToken.cs:line 83
       at Raven.Json.Linq.RavenJObject.FromObject(Object o, JsonSerializer jsonSerializer) in c:'Builds'RavenDB-Stable'Raven.Abstractions'Json'Linq'RavenJObject.cs:line 159
       at Raven.Client.Document.EntityToJson.GetObjectAsJson(Object entity) in c:'Builds'RavenDB-Stable'Raven.Client.Lightweight'Document'EntityToJson.cs:line 74
       at Raven.Client.Document.EntityToJson.ConvertEntityToJson(String key, Object entity, RavenJObject metadata) in c:'Builds'RavenDB-Stable'Raven.Client.Lightweight'Document'EntityToJson.cs:line 41
       at Raven.Client.Document.InMemoryDocumentSessionOperations.EntityChanged(Object entity, DocumentMetadata documentMetadata) in c:'Builds'RavenDB-Stable'Raven.Client.Lightweight'Document'InMemoryDocumentSessionOperations.cs:line 1033
       at Raven.Client.Document.InMemoryDocumentSessionOperations.<PrepareForEntitiesPuts>b__14(KeyValuePair`2 pair) in c:'Builds'RavenDB-Stable'Raven.Client.Lightweight'Document'InMemoryDocumentSessionOperations.cs:line 908
       at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()
       at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
       at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
       at Raven.Client.Document.InMemoryDocumentSessionOperations.PrepareForEntitiesPuts(SaveChangesData result) in c:'Builds'RavenDB-Stable'Raven.Client.Lightweight'Document'InMemoryDocumentSessionOperations.cs:line 908
       at Raven.Client.Document.InMemoryDocumentSessionOperations.PrepareForSaveChanges() in c:'Builds'RavenDB-Stable'Raven.Client.Lightweight'Document'InMemoryDocumentSessionOperations.cs:line 901
       at Raven.Client.Document.DocumentSession.SaveChanges() in c:'Builds'RavenDB-Stable'Raven.Client.Lightweight'Document'DocumentSession.cs:line 694
       at Pendragon.Infrastructure.ActivityLogger.<>c__DisplayClass2.<Log>b__1() in c:'Users'me'repos'project'project'Infrastructure'Logger.cs:line 103
       at System.Threading.Tasks.Task.InnerInvoke()
       at System.Threading.Tasks.Task.Execute()

我在这里没有任何线索，所以任何帮助

ActivityLogger.Instance.Log(item, session);

new ActivityLogger().Log(item, session);