如何控制.Net 5 Web API中Serilog的日志输出内容？

在.Net 5 Web API项目中使用Serilog实现日志记录，功能运行正常，但日志文件生成了大量非必要的额外信息（如System.Net.Http相关的HTTP请求处理日志），仅需记录指定的业务日志，如何控制Serilog的日志输出范围？

日志文件内容示例 #

2022-08-19T11:18:48.4609958-07:00 [Information] () Application Starting.##############3
2022-08-19T11:19:25.0417644-07:00 [Information] (LAFitness.SpotReservation.WebAPI.Queries.Query) GraphQL would be calling the following URL: https://localhost:5001/
2022-08-19T11:19:25.0695842-07:00 [Information] (System.Net.Http.HttpClient.GraphQLService.LogicalHandler) Start processing HTTP request "GET" https://localhost:5001/rooms/89
2022-08-19T11:19:25.0714494-07:00 [Information] (System.Net.Http.HttpClient.GraphQLService.ClientHandler) Sending HTTP request "GET" https://localhost:5001/rooms/89
2022-08-19T11:19:27.6939187-07:00 [Information] (System.Net.Http.HttpClient.GraphQLService.ClientHandler) Received HTTP response headers after 2616.3589ms - 200
2022-08-19T11:19:27.6956126-07:00 [Information] (System.Net.Http.HttpClient.GraphQLService.LogicalHandler) End processing HTTP request after 2633.29ms - 200

当前appsettings.json中的Serilog配置 #

"Serilog": {
  "MinimumLevel": "Information",
  "WriteTo": [
    {
      "Name": "File",
      "Args": {
        "path": "Logs/applog_.log",
        "outputTemplate": "{Timestamp:o} [{Level}] ({SourceContext}) {Message}{NewLine}{Exception}",
        "rollingInterval": "Day",
        "retainedFileCountLimit": 30
      }
    }
  ],
  "Filter": [
    {
      "Name": "ByExcluding",
      "Args": {
        "expression": "StartsWith(SourceContext, 'Microsoft.')"
      }
    }
  ]
}

解决方案 #

有三种核心方式可以精准控制Serilog的日志输出范围，保留业务日志：

1. 扩展过滤规则，排除System开头的日志 #

当前配置仅排除了Microsoft.开头的日志，冗余的HTTP日志来自System.Net.Http命名空间。只需修改Filter表达式，同时排除Microsoft.和System.开头的日志：

修改后的Serilog配置：

"Serilog": {
  "MinimumLevel": "Information",
  "WriteTo": [
    {
      "Name": "File",
      "Args": {
        "path": "Logs/applog_.log",
        "outputTemplate": "{Timestamp:o} [{Level}] ({SourceContext}) {Message}{NewLine}{Exception}",
        "rollingInterval": "Day",
        "retainedFileCountLimit": 30
      }
    }
  ],
  "Filter": [
    {
      "Name": "ByExcluding",
      "Args": {
        "expression": "StartsWith(SourceContext, 'Microsoft.') or StartsWith(SourceContext, 'System.')"
      }
    }
  ]
}

2. 仅包含业务命名空间的日志（最精准） #

如果业务日志都来自特定命名空间（比如示例中的LAFitness.SpotReservation.WebAPI），可以改用ByIncludingOnly规则，只保留符合条件的日志，彻底过滤所有非业务日志：

修改后的配置：

"Serilog": {
  "MinimumLevel": "Information",
  "WriteTo": [
    {
      "Name": "File",
      "Args": {
        "path": "Logs/applog_.log",
        "outputTemplate": "{Timestamp:o} [{Level}] ({SourceContext}) {Message}{NewLine}{Exception}",
        "rollingInterval": "Day",
        "retainedFileCountLimit": 30
      }
    }
  ],
  "Filter": [
    {
      "Name": "ByIncludingOnly",
      "Args": {
        "expression": "StartsWith(SourceContext, 'LAFitness.SpotReservation.WebAPI')"
      }
    }
  ]
}

3. 单独调整HttpClient的日志级别 #

如果需要保留部分HttpClient日志但减少冗余，可以单独设置System.Net.Http的最低日志级别为Warning或更高，仅记录警告及以上级别的相关日志：

"Serilog": {
  "MinimumLevel": {
    "Default": "Information",
    "Override": {
      "System.Net.Http": "Warning"
    }
  },
  "WriteTo": [
    {
      "Name": "File",
      "Args": {
        "path": "Logs/applog_.log",
        "outputTemplate": "{Timestamp:o} [{Level}] ({SourceContext}) {Message}{NewLine}{Exception}",
        "rollingInterval": "Day",
        "retainedFileCountLimit": 30
      }
    }
  ],
  "Filter": [
    {
      "Name": "ByExcluding",
      "Args": {
        "expression": "StartsWith(SourceContext, 'Microsoft.')"
      }
    }
  ]
}

内容的提问来源于stack exchange，提问作者shujaat siddiqui