linq - 从 Azure 云表删除时出错 - ResourceNotFound

Question

我在从 azure 表中删除对象时遇到间歇性问题。它只影响我大约 1% 的尝试，如果稍后再次进行相同的调用，那么它工作正常，但我很想找出背后的原因!我在谷歌上搜索了一下，发现缺乏关于如何创建非常可靠的删除、插入和更新代码的文档，这令人非常惊讶……这一切似乎有点碰运气，”尝试一下，大多数时候都会有效”

编辑:我将删除此问题中最初的文本，并将其替换为全新的文本，以考虑我已经尝试/建议的内容。

Azure 表会像 SQL Azure 一样遭受间歇性故障吗？如果是这样，我会认为“saveChangesWithRetries”会处理这个问题吗？这是错误的吗？

所以...相当简单的代码，在 Azure Web 角色上每分钟被调用大约 250 次。 azure 表用作消息传递系统的一部分。消息由一个用户插入，由另一个用户下载，成功下载后，这些消息将被标记为已读。

每个用户都有一个用于未读消息的分区和一个用于已读消息的分区。因此，要将消息标记为“已读”，请将其从未读分区中删除并移动到已读分区中。

在每分钟调用此代码 250 次的情况下，我将在最终的 SaveChangesWithRetries() 中收到 2 到 10 个以下错误。内部异常是:

ResourceNotFound The specified resource does not exist. RequestId:652a3e13-3911-4503-8e49-6fec32a3c044 Time:2011-09-28T22:09:39.0795651Z

我不认为单个分区每分钟被访问的次数不会超过几次。

这是我的代码:

    public static void Message_MarkAsRead(int uid)
    {
        try
        {
            storageAccount = CloudStorageAccount.Parse(connectionString);
            tableClient = new CloudTableClient(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials);
            tableClient.RetryPolicy = RetryPolicies.Retry(retryAmount, TimeSpan.FromSeconds(retrySeconds));

            TableServiceContext tableServiceContext = tableClient.GetDataServiceContext();
            tableServiceContext.IgnoreResourceNotFoundException = true;

            //the messageUserJoinerTable let's us join messageId to userFromId and userToId
            //each message is inserted into the tables twice, once into the userFromId partition and also into the userToId partition
            #region get the userToId and userFromId for this message uid
            List<int> userIds = new List<int>();
            var resultsUserIds = from messagesUserJoinerTable in tableServiceContext.CreateQuery<MessageUserJoinerDataEntity>(messageUserJoinerTableName)
                                where messagesUserJoinerTable.PartitionKey == uid.ToString()
                                select messagesUserJoinerTable;

            foreach (MessageUserJoinerDataEntity messageUserJoiner in resultsUserIds)
            {
                userIds.Add(messageUserJoiner.UserId);
            }
            #endregion

            #region then we need to check the partition for each of these users and mark the messages as read
            if (userIds.Count > 0)
            {
                foreach (int userId in userIds)
                {
                    var resultsUnreadMessages = from messagesTable in tableServiceContext.CreateQuery<MessageDataEntity>(messageTableName)
                                                where messagesTable.PartitionKey == CreatePartitionKey(userId, false)
                                                && messagesTable.RowKey == CreateRowKey(uid)
                                                select messagesTable;

                    //there should only ever be one as duplicate partition/rowkey is not allowed
                    MessageDataEntity messageUnread = resultsUnreadMessages.FirstOrDefault();

                    if (messageUnread != null)
                    {
                        bool isUnreadMessageDeleted = false;

                        //shallow copy the message for re-inserting as read
                        MessageDataEntity messageRead = new MessageDataEntity(messageUnread);

                        //delete the message
                        try
                        {
                            tableServiceContext.Detach(messageUnread);
                            tableServiceContext.AttachTo(messageTableName, messageUnread, "*");
                            tableServiceContext.DeleteObject(messageUnread);
                            //this is where the error occurs
                            tableServiceContext.SaveChangesWithRetries();

                            isUnreadMessageDeleted = true;
                        }
                        catch (Exception ex)
                        {
                            MyTrace.Trace("AzureCloudTable_" + Service.versionForTracing + ".Message_MarkAsRead. Error.Stage.1: MessageID:" + uid + ", UserID:" + userId + ". " + ex.Message + ex.StackTrace + ", " + ex.InnerException.Message + ex.InnerException.StackTrace, "Error. MarkAsRead");

                            //check to see if the message we tried to delete has already been deleted
                            //if so, we just consume this error and continue by inserting the read message
                            //else, we throw the exception outwards
                            var resultsUnreadMessagesLastCheck = from messagesTable in tableServiceContext.CreateQuery<MessageDataEntity>(messageTableName)
                                                                 where messagesTable.PartitionKey == CreatePartitionKey(userId, false)
                                                                 && messagesTable.RowKey == CreateRowKey(uid)
                                                                 select messagesTable;

                            //there should only ever be one as duplicate partition/rowkey is not allowed
                            MessageDataEntity messageUnreadLastCheck = resultsUnreadMessages.FirstOrDefault();

                            if (messageUnreadLastCheck != null)
                            {
                                MyTrace.Trace("AzureCloudTable_" + Service.versionForTracing + ".Message_MarkAsRead. Error.Stage.2: MessageID:" + uid + ", UserID:" + userId + ". Message WAS deleted.", "Error. MarkAsRead");

                                //the message IS deleted, so although I don't understand why getting error in the first 
                                //place, the result should be the same
                                throw ex;
                            }
                            else
                            {
                                //the message is NOT deleted, so we may as well give up now as I don't understand
                                //what's going on
                                MyTrace.Trace("AzureCloudTable_" + Service.versionForTracing + ".Message_MarkAsRead. Error.Stage.2: MessageID:" + uid + ", UserID:" + userId + ". Message was NOT deleted.", "Error. MarkAsRead");
                            }
                        }

                        //mark the new message as read
                        if (isUnreadMessageDeleted)
                        {
                            messageRead.PartitionKey = CreatePartitionKey(userId, true);
                            messageRead.IsRead = true;

                            //check if read message already exists in storage, if not, insert
                            var resultsReadMessages = from messagesTable in tableServiceContext.CreateQuery<MessageDataEntity>(messageTableName)
                                                      where messagesTable.PartitionKey == CreatePartitionKey(userId, true)
                                                      && messagesTable.RowKey == CreateRowKey(uid)
                                                      select messagesTable;

                            //do the insert
                            if (resultsReadMessages.FirstOrDefault() == null)
                            {
                                tableServiceContext.AddObject(messageTableName, messageRead);
                                tableServiceContext.SaveChangesWithRetries();
                            }
                        }
                    }
                }
            }
            #endregion
        }
        catch (Exception ex)
        {
            try
            {
                MyTrace.Trace("AzureCloudTable_" + Service.versionForTracing + ".Message_MarkAsRead. Error: " + ex.Message + ex.StackTrace + ", " + ex.InnerException.Message + ex.InnerException.StackTrace, "Error. MarkAsRead");
            }
            catch (Exception)
            {
                MyTrace.Trace("AzureCloudTable_" + Service.versionForTracing + ".Message_MarkAsRead. Error: " + ex.Message + ex.StackTrace, "Error. MarkAsRead");
            }
        }
    }

我不明白当资源作为查询的一部分返回给我，然后我对其进行了 != null 检查时，资源怎么可能不存在。

根据之前的响应，我添加了代码来在尝试中进行额外的检查，以查看该对象是否已被以某种方式删除。 尚未删除

我的跟踪在发生错误时返回此信息:

AzureCloudTable_3_0_5.Message_MarkAsRead. Error.Stage.1: MessageID:146751012, BoyID:477296. An error occurred while processing this request. at Microsoft.WindowsAzure.StorageClient.Tasks.Task1.get_Result() at Microsoft.WindowsAzure.StorageClient.Tasks.Task1.ExecuteAndWait() at BenderRestfulService_3_0_5.AzureCloudTable.Message_MarkAsRead(Int32 uid) in ... ResourceNotFound The specified resource does not exist. RequestId:583c59df-fdac-47e4-a03c-7a4bc7d004c9 Time:2011-10-05T16:37:36.7940530Z at System.Data.Services.Client.DataServiceContext.SaveResult.d__1e.MoveNext()

AzureCloudTable_3_0_5.Message_MarkAsRead. Error.Stage.2: MessageID:146751012, BoyID:477296. Message was NOT deleted.

我完全困惑了。非常感谢任何建议!!!

史蒂文

Answer 1

此代码是否在多个角色实例或多个应用程序中运行？ (也许在您从表中读取实体的时间和尝试删除它的时间之间，该实体正在被另一个进程删除。)