如何使用ASP.NET Core日志记录懒惰？

Question

假设这样的场景:

[Route("api/test")]
public class TestController
{
    private readonly ILogger<TestController> logger;

    public TestController(ILogger<TestController> logger)
    {
        this.logger = logger;
    }

    [HttpPut]
    public void Put(Guid id, [FromBody]FooModel model)
    {
        logger.LogInformation($"Putting {id}");
        logger.LogTrace("Putting model {0}", Newtonsoft.Json.JsonConvert.SerializeObject(model));
        try
        {
            // Omitted: actual PUT operation.
        }
        catch (Exception ex)
        {
            logger.LogError("Exception {0}", ex);
        }
    }
}

public class FooModel 
{ 
    string Bar { get; set; } 
}

在这种情况下,LogInformation呼叫将触发一个string.Format电话,甚至更糟的是,该LogTrace行会触发一个SerializeObject电话,不管LogLevel.这似乎相当浪费.

Logging API中是否存在允许更懒惰的方法？我能想到的唯一解决方法是覆盖ToString模型以创建非常详细的表示,并跳过使用JsonConvert.SerializeObject作为工具.

Answer 1

所述ILogger接口提供的IsEnabled方法:

if (logger.IsEnabled(LogLevel.Information))
{
    logger.LogInformation($"Putting {id}");
}

if (logger.IsEnabled(LogLevel.Trace))
{
    logger.LogTrace("Putting model {0}", Newtonsoft.Json.JsonConvert.SerializeObject(model));
}

你会在GitHub上找到默认的实现:https://github.com/aspnet/Extensions/blob/master/src/Logging/Logging/src/Logger.cs#L53