c# - 使用 C# 的 MongoDb 响应缓慢

Question

我最近一直致力于设置 Mongo 数据库服务器来充当网站的对象缓存。然而，在设置完所有内容后，我担心性能会相当慢。

它是单个服务器，不是副本集或分片的一部分。我正在从本地计算机到 Windows Azure VM 上的服务器运行所有测试。

例如，我收集了大约 5,500 个文档，其中每个文档都存储一个指向外部站点的链接。典型的文档如下所示:

{ 
    "_id" : 5001 , 
    "Active" : true , 
    "CategoryId" : 1 , 
    "Crci" : "V" , 
    "CultureId" :  null,
    "DateUpdated" : { "$date" : 1333370987810} ,
    "Description" : "National Careers Service: Childminder" ,
    "Keywords" :  null ,
    "MaxLevel" :  null ,
    "MinLevel" :  null ,
    "PhoneNumber" :  null ,
    "Priority" : 1 , 
    "Title" : "National Careers Service: Childminder" ,
    "WebUrl" : "https://nationalcareersservice.direct.gov.uk/advice/planning/jobprofiles/Pages/childminder.aspx"
}

我使用官方 10gen 驱动程序在代码中尝试了以下示例查询，平均需要 2.7-3.0 秒才能完成:

var query = (from er in lib.All()
             where er.Id > 7000
             select er);

(lib 是一个瘦包装类，All() 公开了 IQuerable 接口(interface))

上面的查询返回大约 3000 条记录。

我已经检查了 linq 生成的查询，它似乎没问题:

{_id: { $gt: 7000} }

从umongo(GUI 界面)运行相同的查询会在不到一秒的时间内返回结果，这更符合我的预期。

使用确保索引正确索引字段(填充集合时调用一次，之后这是只读数据:

collection.EnsureIndex(new IndexKeysBuilder<ExternalResourceView>().Ascending(er => er.Id), IndexOptions.SetUnique(true));
collection.EnsureIndex(new IndexKeysBuilder<ExternalResourceView>().Ascending(er => er.CategoryId));
collection.EnsureIndex(new IndexKeysBuilder<ExternalResourceView>().Ascending(er => er.Active));
collection.EnsureIndex(new IndexKeysBuilder<ExternalResourceView>().Ascending(er => er.Keywords));

索引似乎用于搜索:

db.ExternalResources.find({_id: {$gt: 7000}}).explain()

{
        "cursor" : "BtreeCursor _id_",
        "isMultiKey" : false,
        "n" : 3087,
        "nscannedObjects" : 3087,
        "nscanned" : 3087,
        "nscannedObjectsAllPlans" : 3087,
        "nscannedAllPlans" : 3087,
        "scanAndOrder" : false,
        "indexOnly" : false,
        "nYields" : 0,
        "nChunkSkips" : 0,
        "millis" : 5,
        "indexBounds" : {
                "_id" : [
                        [
                                7000,
                                1.7976931348623157e+308
                        ]
                ]
        },
        "server" : <Server Name>
}

即使是单个直接 ID 查找也需要近 100 毫秒才能在代码中返回，例如:

 from er in lib.All()
 where er.Id == 3100
 select er

我是否缺少任何可以加快搜索速度的设置，或者我的期望一开始就不切实际？

编辑:我已经尝试完全重建/重新填充数据库，但仍然感觉慢得令人无法接受

编辑2:我将整个包装类包含在内。我不认为这是有问题的，但以防万一:

public abstract class MongoLibrary<TViewModel> : ILibrary<TViewModel> where TViewModel : class
{
    private readonly MongoCollection _collection;
    private readonly string _dbName;
    private readonly string _collectionName;
    private readonly string _connString;

    protected MongoLibrary(string connString, string dbName, string collectionName)
    {
        _connString = connString;
        connString += "/" + dbName;
        var client = new MongoClient(connString);
        _dbName = dbName;
        _collectionName = collectionName;
        var db = client.GetServer().GetDatabase(dbName);
        _collection = db.GetCollection<TViewModel>(collectionName);
    }

    public abstract void ConfigureIndex(MongoCollection collection);

    public IQueryable<TViewModel> All()
    {
        return _collection.AsQueryable<TViewModel>();
    }

    public IEnumerable<TViewModel> GetWhere(Func<TViewModel, bool> predicate)
    {
        return _collection.AsQueryable<TViewModel>().Where(predicate);
    }

    protected void PopulateData(IEnumerable<TViewModel> views, int instanceToUpdate)
    {
        var ports = //port numbers hidden for security

        foreach (var port in ports)
        {
            var client = new MongoClient(string.Format("{0}:{1}/{2}", _connString, port, _dbName));

            var db = client.GetServer().GetDatabase(_dbName);
            var coll = db.GetCollection(_collectionName);
            coll.Drop();
            coll.InsertBatch(views);
        }
        ConfigureIndex(_collection);
    }

}

编辑 3:服务器日志分析对数据库的查询:

该查询只是为了展示性能而进行的人工查询。查询是:

        var sw = new Stopwatch();
        sw.Start();
        var temp = _externalResourceLibrary.All().Where(er => er.Id > 7500).ToList();
        sw.Stop();

您可以从日志中看到它经过身份验证，然后在 2 趟中检索了数据。总共检索到 2677 份文件。所用时间为 3580 毫秒(5 次运行的平均值)

>db.system.profile.find().limit(10).sort( { ts : -1 } ).pretty()  
{
    "op" : "getmore",
    "ns" : "cache.ExternalResources",
    "query" : {
        "_id" : {
            "$gt" : 7500
        }
    },
    "cursorid" : NumberLong("949848842778037962"),
    "ntoreturn" : 0,
    "keyUpdates" : 0,
    "numYield" : 0,
    "lockStats" : {
        "timeLockedMicros" : {
            "r" : NumberLong(9486),
            "w" : NumberLong(0)
        },
        "timeAcquiringMicros" : {
            "r" : NumberLong(4),
            "w" : NumberLong(5)
        }
    },
    "nreturned" : 2576,
    "responseLength" : 1511874,
    "millis" : 9,
    "ts" : ISODate("2014-01-28T10:52:16.125Z"),
    "client" : <ipAddress>,
    "allUsers" : [
                    {
                        "user" : <username>,
                        "userSource" : <dbName>;
                    }
    ],
    "user" : <username>@<dbName>;
}
{
    "op" : "query",
    "ns" : "cache.ExternalResources",
    "query" : {
            "_id" : {
                    "$gt" : 7500
            }
    },
    "cursorid" : NumberLong("949848842778037962"),
    "ntoreturn" : 0,
    "ntoskip" : 0,
    "nscanned" : 102,
    "keyUpdates" : 0,
    "numYield" : 0,
    "lockStats" : {
            "timeLockedMicros" : {
                    "r" : NumberLong(749),
                    "w" : NumberLong(0)
            },
            "timeAcquiringMicros" : {
                    "r" : NumberLong(5),
                    "w" : NumberLong(3)
            }
    },
    "nreturned" : 101,
    "responseLength" : 64013,
    "millis" : 0,
    "ts" : ISODate("2014-01-28T10:52:15.954Z"),
    "client" : <ipAddress>,
    "allUsers" : [
            {
                    "user" : <username>,
                    "userSource" : <dbName>;
            }
    ],
    "user" : <username>@<dbName>;
}
{
    "op" : "command",
    "ns" : "cache.$cmd",
    "command" : {
            "authenticate" : 1,
            "user" : <username>,
            "nonce" : <nonce>;,
            "key" : <key>;
    },
    "ntoreturn" : 1,
    "keyUpdates" : 0,
    "numYield" : 0,
    "lockStats" : {
            "timeLockedMicros" : {
                    "r" : NumberLong(381),
                    "w" : NumberLong(0)
            },
            "timeAcquiringMicros" : {
                    "r" : NumberLong(9),
                    "w" : NumberLong(3)
            }
    },
    "responseLength" : 79,
    "millis" : 0,
    "ts" : ISODate("2014-01-28T10:52:15.938Z"),
    "client" : <ipAddress>,
    "allUsers" : [
            {
                    "user" : <username>,
                    "userSource" : <dbName>
            }
    ],
    "user" : <username>@<dbName>;
}

Answer 1

问题是由网络延迟引起的