.net core日志系统相关总结

影者东升

目录

• 前言
  
• 正文
  

前言

本节开始整理日志相关的东西。先整理一下日志的基本原理。

正文

首先介绍一下包:
1.Microsoft.Extengsion.Logging.Abstrations
这个是接口包。
2.Microsoft.Extengsion.Logging
这个是实现包
3.Microsoft.Extengsion.Logging.Console
这个是扩展包
代码如下:

static void Main(string[] args)
{
IConfigurationBuilder configurationBuilder = new ConfigurationBuilder();
configurationBuilder.AddJsonFile("appsettings.json",optional:false,reloadOnChange:true);
var config = configurationBuilder.Build();
IServiceCollection serviceCollection = new ServiceCollection();
serviceCollection.AddSingleton<IConfiguration>(p=>config);
serviceCollection.AddLogging(builder =>
{
builder.AddConfiguration(config.GetSection("Logging"));
builder.AddConsole();
});
IServiceProvider service = serviceCollection.BuildServiceProvider();
ILoggerFactory loggerFactory = service.GetService<ILoggerFactory>();
var loggerObj = loggerFactory.CreateLogger("Default");
loggerObj.LogInformation(2021, "Default,now that is 2021");
var loggerObj2 = loggerFactory.CreateLogger("loggerObj");
loggerObj2.LogDebug(2021, "loggerObj,now that is 2021");
Console.ReadKey();
}

配置文件:

{
  "Logging": {
  "LogLevel": {
    "Default": "Debug",
    "Microsoft": "Warning",
    "Microsoft.Hosting.Lifetime": "Information"
  },
  "Console": {
    "LogLevel": {
    "Default": "Information",
    "Program": "Trace",
    "loggerObj": "Debug"
    }
  }
  }
}

结果:

首先是配置级别的问题,查看loglevel 文件:

public enum LogLevel
{
/// <summary>Logs that contain the most detailed messages. These messages may contain sensitive application data.
/// These messages are disabled by default and should never be enabled in a production environment.</summary>
Trace,
/// <summary>Logs that are used for interactive investigation during development.  These logs should primarily contain
/// information useful for debugging and have no long-term value.</summary>
Debug,
/// <summary>Logs that track the general flow of the application. These logs should have long-term value.</summary>
Information,
/// <summary>Logs that highlight an abnormal or unexpected event in the application flow, but do not otherwise cause the
/// application execution to stop.</summary>
Warning,
/// <summary>Logs that highlight when the current flow of execution is stopped due to a failure. These should indicate a
/// failure in the current activity, not an application-wide failure.</summary>
Error,
/// <summary>Logs that describe an unrecoverable application or system crash, or a catastrophic failure that requires
/// immediate attention.</summary>
Critical,
/// <summary>Not used for writing log messages. Specifies that a logging category should not write any messages.</summary>
None,
}

从上之下，依次提高log级别。
比如说设置了log 级别是Error，那么Debug、Information、Warning 都不会被答应出来。
那么就来分析一下代码吧。
AddLogging:

public static IServiceCollection AddLogging(this IServiceCollection services, Action<ILoggingBuilder> configure)
{
if (services == null)
{
throw new ArgumentNullException(nameof(services));
}
services.AddOptions();
services.TryAdd(ServiceDescriptor.Singleton<ILoggerFactory, LoggerFactory>());
services.TryAdd(ServiceDescriptor.Singleton(typeof(ILogger<>), typeof(Logger<>)));
services.TryAddEnumerable(ServiceDescriptor.Singleton<IConfigureOptions<LoggerFilterOptions>>(
new DefaultLoggerLevelConfigureOptions(LogLevel.Information)));
configure(new LoggingBuilder(services));
return services;
}

这里面给注册了ILoggerFactory和ILogger。然后设置了一个打印log的级别配置，LogLevel.Information，这个就是如果我们没有配置文件默认就是Information这种级别了。
configure(new LoggingBuilder(services)) 给我们的委托提供了一个LoggingBuilder的实例化对象。这个对象就是用来专门做扩展的，是解耦的一种方式。

internal class LoggingBuilder : ILoggingBuilder
{
public LoggingBuilder(IServiceCollection services)
{
Services = services;
}
public IServiceCollection Services { get; }
}

这个LoggingBuilder 类基本什么功能都没有，但是因为有了这样一个类，就可以作为扩展的标志了。
比如说上文的:

builder.AddConfiguration(config.GetSection("Logging"));
builder.AddConsole();

看下AddConfiguration:

public static ILoggingBuilder AddConfiguration(this ILoggingBuilder builder, IConfiguration configuration)
{
builder.AddConfiguration();
builder.Services.AddSingleton<IConfigureOptions<LoggerFilterOptions>>(new LoggerFilterConfigureOptions(configuration));
builder.Services.AddSingleton<IOptionsChangeTokenSource<LoggerFilterOptions>>(new ConfigurationChangeTokenSource<LoggerFilterOptions>(configuration));
builder.Services.AddSingleton(new LoggingConfiguration(configuration));
return builder;
}

这里面给我们注入了配置文件的配置:builder.Services.AddSingleton<IConfigureOptions>(new LoggerFilterConfigureOptions(configuration))
同时给我们注册监听令牌:builder.Services.AddSingleton<IOptionsChangeTokenSource>(new ConfigurationChangeTokenSource(configuration));
这里给我们注册配置保存在LoggingConfiguration中：builder.Services.AddSingleton(new LoggingConfiguration(configuration));
因为LoggingConfiguration 保存了，故而我们随时可以获取到LoggingConfiguration 的配置。
看下AddConsole:

/// <param name="builder">The <see cref="ILoggingBuilder"/> to use.</param>
public static ILoggingBuilder AddConsole(this ILoggingBuilder builder)
{
builder.AddConfiguration();
builder.AddConsoleFormatter<JsonConsoleFormatter, JsonConsoleFormatterOptions>();
builder.AddConsoleFormatter<SystemdConsoleFormatter, ConsoleFormatterOptions>();
builder.AddConsoleFormatter<SimpleConsoleFormatter, SimpleConsoleFormatterOptions>();
builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<ILoggerProvider, ConsoleLoggerProvider>());
LoggerProviderOptions.RegisterProviderOptions<ConsoleLoggerOptions, ConsoleLoggerProvider>(builder.Services);
return builder;
}

builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<ILoggerProvider, ConsoleLoggerProvider>()) 里面给我们ILoggerProvider 增加了一个ConsoleLoggerProvider，故而我们多了一个打印的功能。
LoggerProviderOptions.RegisterProviderOptions<ConsoleLoggerOptions, ConsoleLoggerProvider>(builder.Services) 给我们加上了ConsoleLoggerOptions 绑定为ConsoleLoggerProvider的配置。
RegisterProviderOptions 如下:

public static void RegisterProviderOptions<TOptions, TProvider>(IServiceCollection services) where TOptions : class
{
services.TryAddEnumerable(ServiceDescriptor.Singleton<IConfigureOptions<TOptions>, LoggerProviderConfigureOptions<TOptions, TProvider>>());
services.TryAddEnumerable(ServiceDescriptor.Singleton<IOptionsChangeTokenSource<TOptions>, LoggerProviderOptionsChangeTokenSource<TOptions, TProvider>>());
}

接下来就是调用服务:

var loggerObj = loggerFactory.CreateLogger("Default");
loggerObj.LogInformation(2021, "Default,now that is 2021");

看下LoggerFactory的CreateLogger：

public ILogger CreateLogger(string categoryName)
{
if (CheckDisposed())
{
throw new ObjectDisposedException(nameof(LoggerFactory));
}
lock (_sync)
{
if (!_loggers.TryGetValue(categoryName, out Logger logger))
{
logger = new Logger
{
Loggers = CreateLoggers(categoryName),
};
(logger.MessageLoggers, logger.ScopeLoggers) = ApplyFilters(logger.Loggers);
_loggers[categoryName] = logger;
}
return logger;
}
}

里面做了缓存，如果categoryName有缓存的话直接使用缓存，如果没有那么调用CreateLoggers创建。
查看CreateLoggers:

private LoggerInformation[] CreateLoggers(string categoryName)
{
var loggers = new LoggerInformation[_providerRegistrations.Count];
for (int i = 0; i < _providerRegistrations.Count; i++)
{
loggers[i] = new LoggerInformation(_providerRegistrations[i].Provider, categoryName);
}
return loggers;
}

这里面就用我们前面注册过的全部logger的provider，封装进LoggerInformation。
查看LoggerInformation:

internal readonly struct LoggerInformation
{
public LoggerInformation(ILoggerProvider provider, string category) : this()
{
ProviderType = provider.GetType();
Logger = provider.CreateLogger(category);
Category = category;
ExternalScope = provider is ISupportExternalScope;
}
public ILogger Logger { get; }
public string Category { get; }
public Type ProviderType { get; }
public bool ExternalScope { get; }
}

里面调用了我们，每个provider的CreateLogger。
那么这个时候我们就找一个provider 看下CreateLogger到底做了什么，这里就找一下ConsoleLoggerProvider，因为我们添加了这个。

[ProviderAlias("Console")]
 public class ConsoleLoggerProvider : ILoggerProvider, ISupportExternalScope
{
    private readonly IOptionsMonitor<ConsoleLoggerOptions> _options;
    public ILogger CreateLogger(string name)
    {
      if (_options.CurrentValue.FormatterName == null || !_formatters.TryGetValue(_options.CurrentValue.FormatterName, out ConsoleFormatter logFormatter))
      {
#pragma warning disable CS0618
        logFormatter = _options.CurrentValue.Format switch
        {
          ConsoleLoggerFormat.Systemd => _formatters[ConsoleFormatterNames.Systemd],
          _ => _formatters[ConsoleFormatterNames.Simple],
        };
        if (_options.CurrentValue.FormatterName == null)
        {
          UpdateFormatterOptions(logFormatter, _options.CurrentValue);
        }
#pragma warning disable CS0618
      }
      return _loggers.GetOrAdd(name, loggerName => new ConsoleLogger(name, _messageQueue)
      {
        Options = _options.CurrentValue,
        ScopeProvider = _scopeProvider,
        Formatter = logFormatter,
      });
    }
}

看到这个IOptionsMonitor，就知道console 配置是支持热更新的，里面创建了ConsoleLogger，这个ConsoleLogger就是用来打log正在的调用类。
值得注意的是_messageQueue这个，看了打印log还是有一个队列的，按照先进先出原则。
那么最后来看一下loggerObj.LogInformation(2021, "Default,now that is 2021");:

第一层
public static void LogInformation(this ILogger logger, EventId eventId, string message, params object[] args)
{
logger.Log(LogLevel.Information, eventId, message, args);
}
第二层
public static void Log(this ILogger logger, LogLevel logLevel, EventId eventId, string message, params object[] args)
{
     logger.Log(logLevel, eventId, null, message, args);
}
第三层
public static void Log(this ILogger logger, LogLevel logLevel, EventId eventId, Exception exception, string message, params object[] args)
{
if (logger == null)
{
throw new ArgumentNullException(nameof(logger));
}
logger.Log(logLevel, eventId, new FormattedLogValues(message, args), exception, _messageFormatter);
}

那么这个logger.Log 是调用具体某个logger，像consoleLogger 吗？ 不是，我们看LoggerFactory的CreateLogger时候封装了：

logger = new Logger
{
     Loggers = CreateLoggers(categoryName),
};

那么看下Logger的Log到底干了什么。

internal class Logger : ILogger
{
public LoggerInformation[] Loggers { get; set; }
public MessageLogger[] MessageLoggers { get; set; }
public ScopeLogger[] ScopeLoggers { get; set; }
public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
{
MessageLogger[] loggers = MessageLoggers;
if (loggers == null)
{
return;
}
List<Exception> exceptions = null;
for (int i = 0; i < loggers.Length; i++)
{
ref readonly MessageLogger loggerInfo = ref loggers[i];
if (!loggerInfo.IsEnabled(logLevel))
{
continue;
}
LoggerLog(logLevel, eventId, loggerInfo.Logger, exception, formatter, ref exceptions, state);
}
if (exceptions != null && exceptions.Count > 0)
{
ThrowLoggingError(exceptions);
}
static void LoggerLog(LogLevel logLevel, EventId eventId, ILogger logger, Exception exception, Func<TState, Exception, string> formatter, ref List<Exception> exceptions, in TState state)
{
try
{
logger.Log(logLevel, eventId, state, exception, formatter);
}
catch (Exception ex)
{
if (exceptions == null)
{
exceptions = new List<Exception>();
}
exceptions.Add(ex);
}
}
}
}

里面循环判断是否当前级别能够输出：!loggerInfo.IsEnabled(logLevel)
然后调用对应的具体ILog实现的Log，这里贴一下ConsoleLogger 的实现:

[ThreadStatic]
private static StringWriter t_stringWriter;
public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
{
if (!IsEnabled(logLevel))
{
return;
}
if (formatter == null)
{
throw new ArgumentNullException(nameof(formatter));
}
t_stringWriter ??= new StringWriter();
LogEntry<TState> logEntry = new LogEntry<TState>(logLevel, _name, eventId, state, exception, formatter);
Formatter.Write(in logEntry, ScopeProvider, t_stringWriter);
var sb = t_stringWriter.GetStringBuilder();
if (sb.Length == 0)
{
return;
}
string computedAnsiString = sb.ToString();
sb.Clear();
if (sb.Capacity > 1024)
{
sb.Capacity = 1024;
}
_queueProcessor.EnqueueMessage(new LogMessageEntry(computedAnsiString, logAsError: logLevel >= Options.LogToStandardErrorThreshold));
}

把这个队列的也贴一下，比较经典吧。

internal class ConsoleLoggerProcessor : IDisposable
{
private const int _maxQueuedMessages = 1024;
private readonly BlockingCollection<LogMessageEntry> _messageQueue = new BlockingCollection<LogMessageEntry>(_maxQueuedMessages);
private readonly Thread _outputThread;
public IConsole Console;
public IConsole ErrorConsole;
public ConsoleLoggerProcessor()
{
// Start Console message queue processor
_outputThread = new Thread(ProcessLogQueue)
{
IsBackground = true,
Name = "Console logger queue processing thread"
};
_outputThread.Start();
}
public virtual void EnqueueMessage(LogMessageEntry message)
{
if (!_messageQueue.IsAddingCompleted)
{
try
{
_messageQueue.Add(message);
return;
}
catch (InvalidOperationException) { }
}
// Adding is completed so just log the message
try
{
WriteMessage(message);
}
catch (Exception) { }
}
// for testing
internal virtual void WriteMessage(LogMessageEntry entry)
{
IConsole console = entry.LogAsError ? ErrorConsole : Console;
console.Write(entry.Message);
}
private void ProcessLogQueue()
{
try
{
foreach (LogMessageEntry message in _messageQueue.GetConsumingEnumerable())
{
WriteMessage(message);
}
}
catch
{
try
{
_messageQueue.CompleteAdding();
}
catch { }
}
}
public void Dispose()
{
_messageQueue.CompleteAdding();
try
{
_outputThread.Join(1500); // with timeout in-case Console is locked by user input
}
catch (ThreadStateException) { }
}
}

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