庆军之假wal系统的实现记录

要解决的问题:

我有一个系统，但是数据库表示它不稳定了，我需要对外高可用。数据库不能用的时候，总不能不用吧。所以，只能特征一致性。

临时的数据存在文件wal里面，由另一个线程单独处理。

原来是打算用 faster来实现。但是我表示说，文档很好。但是我不会用。我太菜。

最后某网友建议用日志来处理。我写了两天。终于是简单的凑出来了。

我用到了Serilog来写wal.因为不会写它的过滤条件。搞不来轮子。所以指定了 Fatal级别，也就是枚举里面为6的等级来记录到另一个目录下。

具体的配置如下。

//appsettings.json 中 

 1 "WriteTo": [
 2       //{ "Name": "Console" },
 3       {
 4         "Name": "File",
 5         "Args": {
 6           "path": "Log2s\\log.txt",
 7           "rollingInterval": "Day",
 8           "fileSizeLimitBytes": "10485760",
 9           "retainedFileCountLimit": 5,
10           "rollOnFileSizeLimit": true
11         }
12       },
13       {
14         "Name": "Logger",
15         "Args": {
16           "configureLogger": {
17             "Filter": [
18               {
19                 "Name": "ByIncludingOnly",
20                 "Args": {
21                   "expression": "@l = 'Fatal'"
22                 }
23               }
24             ],
25             "WriteTo": [
26               {
27                 "Name": "File",
28                 "Args": {
29                   "outputTemplate": "[{Timestamp:yyyy-MM-dd HH:mm:ss.fff}] {Message:lj}{NewLine}",
30                   //"outputTemplate": "[{Timestamp:g} {Level:u3}] [{SourceContext}] {Message:lj}{NewLine}",
31                   "path": "wal\\wal.log",
32                   "rollingInterval": "Day",
33                   "fileSizeLimitBytes": "10485760",
34                   "retainedFileCountLimit": 200,
35                   "rollOnFileSizeLimit": true,
36                   "formatter": "Serilog.Formatting.Json.JsonFormatter",
37                   "flushToDiskInterval": "00:00:01"//刷盘时间
38                 }
39               }
40             ]
41           }
42         }
43       }
44     ]

代码调用

_logger?.LogCritical( "{@model}", model);

解析类:

 public class ReWALService : BackgroundService
    {
        public class ReWALDefine
        {    
            public long lastWriteTime { get; set; }//文件最后写入的时间,解析的时候
            public string logfile { get; set; }//文件名称
            public long streamPoint { get; set; }//在文件内容的位置
        }

        private readonly ILogger<ReWALService> _logger;
        
        private  string currentFile = "";
        private readonly DirectoryInfo _directoryInfo;
        public ReWALService(ILoggerFactory loggerFactory) 
        {
            this._logger = loggerFactory.CreateLogger<ReWALService>();
            var path = Path.Combine(Directory.GetCurrentDirectory(), "wal");
            _directoryInfo = new DirectoryInfo(path);
            //wallog
            currentFile = Path.Combine( path,"wallog.txt");
        }
        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            try
            {
                if (!File.Exists(currentFile))
                {
                    File.WriteAllText(currentFile, string.Empty);
                }

                while(!stoppingToken.IsCancellationRequested)
                {
                    var wallogContent = File.ReadAllText(currentFile);
                    ReWALDefine _walloginfo = fetchOrCreateDefine(wallogContent);
                    await Task.Delay(100);
                    DateTime oldDateTime = new DateTime(_walloginfo.lastWriteTime);
                    var walrecords = _directoryInfo.GetFiles("*.log").Where(q => q.LastWriteTime >= oldDateTime).Take(1).OrderBy(q => q.LastWriteTime);
                    var firstwalrecord = walrecords.FirstOrDefault(q => string.Compare(q.Name, currentFile, true) == 0);

                    foreach (var item in walrecords)
                    {   
                        _walloginfo.lastWriteTime = item.LastWriteTime.Ticks;
                        if (string.Compare(item.Name,_walloginfo.logfile,true) != 0)
                        {
                            _walloginfo.logfile = item.Name;
                            _walloginfo.streamPoint = 0;
                        }
                        _walloginfo.lastWriteTime += 1;

                        ReadFile(item.Open(FileMode.Open, FileAccess.Read, FileShare.ReadWrite), _walloginfo);
                        File.WriteAllText(currentFile, JsonConvert.SerializeObject(_walloginfo));
                    }
                }
            }
            catch (Exception ex)
            {
                _logger?.LogError(ex.ToString());
            }
        }

        private static ReWALDefine fetchOrCreateDefine(string wallogContent)
        {
            ReWALDefine _walloginfo;
            if (string.IsNullOrWhiteSpace(wallogContent))
            {
                _walloginfo = new ReWALDefine();
            }
            else
            {
                _walloginfo = JsonConvert.DeserializeObject<ReWALDefine>(wallogContent);
            }

            return _walloginfo;
        }private void ReadFile(FileStream fs, ReWALDefine reWALDefine) {
            try
            {
                fs.Position = reWALDefine.streamPoint;
                using (StreamReader sr = new StreamReader(fs, System.Text.Encoding.UTF8))
                {
                    while (sr.Peek() > -1)
                    {
                        Console.WriteLine("T:" + sr.ReadLine());//工作开始
                    }
                    Console.WriteLine(fs.Position);
                    Console.WriteLine(fs.Length);
                    reWALDefine.streamPoint = fs.Length;
                }
            }
            catch (Exception ex)
            {
                _logger?.LogError(ex.ToString());
            }
        }
    }