代码改变世界

基于STSdb和fastJson的磁盘/内存缓存

2013-07-03 10:50 by 灵感之源, ... 阅读, ... 评论, 收藏, 编辑

更新

1. 增加了对批量处理的支持,写操作速度提升5倍,读操作提升100倍

2. 增加了对并发的支持

需求

业务系统用的是数据库,数据量大,部分只读或相对稳定业务查询复杂,每次页面加载都要花耗不少时间(不讨论异步),觉得可以做一下高速缓存,譬如用nosql那种key/value快速存取结果

目的

这里不是要做一个大家都适用的磁盘/内存缓存库,这个做法,部分是展示STSdb的用法,部分是提供一个简单易用的解决方案。

磁盘/内存

为什么不用memcached或者AppFabric Cache这样的现成解决方案呢?因为业务要缓存的内存或大或小,小的几KB,大的几MB,如果用户一多,势必对内存有过度的需求。所以选择做一个基于磁盘的。

当然,这个解决方案是支持内存缓存的。构造的时候传递空字符串便可。

STSdb是什么

再来说明一下STSdb是什么:STSdb是C#写的开源嵌入式数据库和虚拟文件系统,支持实时索引,性能是同类产品的几倍到几十倍,访问官方网站

我之前介绍过:STSdb,最强纯C#开源NoSQL和虚拟文件系统 和 STSdb,最强纯C#开源NoSQL和虚拟文件系统 4.0 RC2 支持C/S架构 ,大家可以先看看。

实现

存取

因为是基于磁盘,所以需要使用到高效的Key/Value存取方案,碰巧我们有STSdb :)

序列化

因为要求简便快速,用的是fastJson

代码

代码比较简单,花了2个小时写的,很多情况没考虑,譬如磁盘空间不足、过期空间回收等,这些留给大家做家庭作业吧。另外,为了发布方便,STSdb和fastJson的代码都合并到一个项目里。

CahceEngine.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using STSdb4.Database;
using fastJSON;
using System.IO;

namespace Com.SuperCache.Engine
{
    public class CacheEngine
    {
        private const string KeyExpiration = "Expiration";
        private string dataPath;
        private static IStorageEngine memoryInstance = null;
        private static object syncRoot = new object();
        private bool isMemory = false;

        public CacheEngine(string DataPath)
        {
            dataPath = DataPath;
            if (!dataPath.EndsWith(Path.DirectorySeparatorChar.ToString()))
                dataPath += Path.DirectorySeparatorChar;

            isMemory = string.IsNullOrEmpty(DataPath);
        }

        public void Add<K>(string Category, K Key, object Data)
        {
            Add(Category, Key, Data, null);
        }

        private IStorageEngine Engine
        {
            get
            {
                if (isMemory)
                {
                    lock (syncRoot)
                    {
                        if (memoryInstance == null)
                            memoryInstance = STSdb.FromMemory();
                    }
                    return memoryInstance;
                }
                else
                    return STSdb.FromFile(GetFile(false), GetFile(true));
            }
        }

        private string GetExpirationTable(string Category)
        {
            return KeyExpiration + "_" + Category;
        }

        public void Add<K, V>(string Category, IEnumerable<KeyValuePair<K, V>> Items, DateTime? ExpirationDate)
        {
            lock (syncRoot)
            {
                var engine = Engine;
                var table = engine.OpenXIndex<K, string>(Category);
                Items.ForEach(i =>
                    {
                        var key = i.Key;
                        var data = i.Value;
                        //will only serialize object other than string
                        var result = typeof(V) == typeof(string) ? data as string : JSON.Instance.ToJSON(data);
                        table[key] = result;
                        table.Flush();

                        //specify expiration
                        var expiration = engine.OpenXIndex<K, DateTime>(GetExpirationTable(Category));
                        //default 30 mins to expire from now
                        var expirationDate = ExpirationDate == null || ExpirationDate <= DateTime.Now ? DateTime.Now.AddMinutes(30) : (DateTime)ExpirationDate;
                        expiration[key] = expirationDate;
                        expiration.Flush();
                    });
                engine.Commit();

                //only dispose disk-based engine
                if (!isMemory)
                    engine.Dispose();
            }
        }

        public void Add<K>(string Category, K Key, object Data, DateTime? ExpirationDate)
        {
            Add<K, object>(Category, new List<KeyValuePair<K, object>> { new KeyValuePair<K, object>(Key, Data) }, ExpirationDate);
        }

        private string GetFile(bool IsData)
        {
            if (!Directory.Exists(dataPath))
                Directory.CreateDirectory(dataPath);
            return dataPath + "SuperCache." + (IsData ? "dat" : "sys");
        }

        public List<KeyValuePair<K, V>> Get<K, V>(string Category, IEnumerable<K> Keys)
        {
            var result = new List<KeyValuePair<K, V>>();
            lock (syncRoot)
            {
                var engine = Engine;
                var table = engine.OpenXIndex<K, string>(Category);
                var expiration = engine.OpenXIndex<K, DateTime>(GetExpirationTable(Category));
                var isCommitRequired = false;

                Keys.ForEach(key =>
                    {
                        string buffer;
                        V value;
                        if (table.TryGet(key, out buffer))
                        {
                            //will only deserialize object other than string
                            value = typeof(V) == typeof(string) ? (V)(object)buffer : JSON.Instance.ToObject<V>(buffer);
                            DateTime expirationDate;
                            //get expiration date
                            if (expiration.TryGet(key, out expirationDate))
                            {
                                //expired
                                if (expirationDate < DateTime.Now)
                                {
                                    value = default(V);
                                    table.Delete(key);
                                    table.Flush();
                                    expiration.Delete(key);
                                    expiration.Flush();
                                    isCommitRequired = true;
                                }
                            }
                        }
                        else
                            value = default(V);

                        result.Add(new KeyValuePair<K, V>(key, value));
                    });

                //only need to commit write actions
                if (isCommitRequired)
                    engine.Commit();

                //only dispose disk-based engine
                if (!isMemory)
                    engine.Dispose();
            }
            return result;
        }

        public V Get<K, V>(string Category, K Key)
        {
            var buffer = Get<K, V>(Category, new K[] { Key });
            var result = buffer.FirstOrDefault();
            return result.Value;
        }
    }
}

  

  

 

新建

构造CacheEngine需要传递缓存保存到哪个文件夹。

基于内存

如果你不喜欢基于磁盘的缓存,可以使用基于内存,构造函数传递空字符串便可。

增加/更新

同一个方法:Add。用户可以指定类型(Category),譬如User,Employee等。键(Key)支持泛型,值(Data)是object。有一个overload是过期日期(ExpirationDate),默认当前时间30分钟后

获取

Get方法需要指定类型(Category)和键(Key)。

 

例子

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Diagnostics;
using Com.SuperCache.Engine;

namespace Com.SuperCache.Test
{
    public class Foo
    {
        public string Name { get; set; }
        public int Age { get; set; }
        public double? Some { get; set; }
        public DateTime? Birthday { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            //TestAddGet();

            //Thread.Sleep(4000);
            //TestExpiration();

            TestPerformance();

            //TestConcurrent();

            Console.Read();
        }

        private static void TestConcurrent()
        {
            var w = new Stopwatch();
            w.Start();
            Parallel.For(1, 3, (a) =>
                {
                    var employees = Enumerable.Range((a - 1) * 1000, a * 1000).Select(i => new KeyValuePair<int, string>(i, "Wilson " + i + " Chen"));
                    var engine = new CacheEngine(@"..\..\data");
                    engine.Add<int, string>("Employee", employees, DateTime.Now.AddMinutes(1));
                });
            w.Stop();
            Console.WriteLine("add:" + w.Elapsed);

            var engine2 = new CacheEngine(@"..\..\data");
            var o = engine2.Get<int, string>("Employee", 1005);
            Console.WriteLine(o);
        }

        private static void TestPerformance()
        {
            var engine = new CacheEngine(@"..\..\data");
            var w = new Stopwatch();

            w.Start();
            var employees = Enumerable.Range(0, 1000).Select(i => new KeyValuePair<int, string>(i, "Wilson " + i + " Chen"));
            engine.Add<int, string>("Employee", employees, DateTime.Now.AddMinutes(1));
            w.Stop();
            Console.WriteLine("add:" + w.Elapsed);

            /*w.Restart();
            employees.ForEach(key =>
                {
                    var o1 = engine.Get<int, string>("Employee", key.Key);
                });
            w.Stop();
            Console.WriteLine("individual get:" + w.Elapsed);*/

            w.Restart();
            var keys = employees.Select(i => i.Key);
            var o = engine.Get<int, string>("Employee", keys);
            w.Stop();
            Debug.Assert(o.Count == keys.Count());
            Console.WriteLine("get:" + w.Elapsed);
        }

        private static void TestExpiration()
        {
            var engine = new CacheEngine(@"..\..\data");
            var o = engine.Get<string, Foo>("User", "wchen");
            Console.WriteLine(o != null ? o.Name : "wchen does not exist or expired");
        }

        private static void TestAddGet()
        {
            var engine = new CacheEngine(@"..\..\data");
            var f = new Foo { Name = "Wilson Chen", Age = 30, Birthday = DateTime.Now, Some = 123.456 };
            engine.Add("User", "wchen", f, DateTime.Now.AddSeconds(5));

            var o = engine.Get<string, Foo>("User", "wchen");
            Console.WriteLine(o.Name);

            var o4 = engine.Get<string, Foo>("User", "foo");
            Console.WriteLine(o4 != null ? o4.Name : "foo does not exist");

            var o3 = engine.Get<string, string>("PlainText", "A");
            Console.WriteLine(o3 ?? "A does not exist");
        }
    }
}

  

  

  

 

说明

项目中引用了System.Management是因为STSdb支持内存数据库,需要判断最大物理内存。如果不喜欢,大家可以移除引用,并且去掉STSdb4.Database.STSdb.FromMemory方法便可。

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