public void AssertThat_Errors_CauseTracesToBeLoggedAsWell()
{
IList <LogEntry> logList = new List <LogEntry>();
var filter = new TriggerableLevelFilter(
CommonLogSeverity.Information,
CommonLogSeverity.Error,
CommonLogSeverity.Trace
);
var outputStream = new ListOutputStream <LogEntry>(logList);
using var logger = new FilteredLogger(
new OutputLogger(outputStream),
filter.Apply
);
logger.LogTrace(new EventId(1, ""), new { });
// assert nothing has been written
Assert.Equal(0, logList.Count);
logger.LogInformation(new EventId(2, ""), new { });
// assert information has been written
Assert.Equal(1, logList.Count);
Assert.Equal(2, logList[0].EventId.Id);
logger.LogError(new EventId(3, ""), new { });
// assert information, trace and error have been written
Assert.Equal(3, logList.Count);
Assert.Equal(2, logList[0].EventId.Id);
Assert.Equal(1, logList[1].EventId.Id);
Assert.Equal(3, logList[2].EventId.Id);
logger.LogTrace(new EventId(4, ""), new { });
// assert information, trace, error an trace have been written
Assert.Equal(4, logList.Count);
Assert.Equal(2, logList[0].EventId.Id);
Assert.Equal(1, logList[1].EventId.Id);
Assert.Equal(3, logList[2].EventId.Id);
Assert.Equal(4, logList[3].EventId.Id);
}
public static IServiceProvider BuildServiceProvider() =>
new ServiceCollection()
// aliasing the ProxyCachingLoggerFactory as transient ILoggerFactory
.AddTransient <ILoggerFactory>(provider =>
provider.GetRequiredService <ProxyCachingLoggerFactory>())
// wrapping the logger with a filter
// it will filter with a minimum log level of "Information"
// if there is a log with a minimum log level of "Error"
// then all previous logs and following logs with a minimum level of "Trace" will also be logged
// new filters (and therefore an empty log cache) will be made because the factory is transient
.Decorate <ILoggerFactory>(factory =>
LoggerFactory(() =>
{
var filter = new TriggerableLevelFilter(
CommonLogSeverity.Information,
CommonLogSeverity.Error,
CommonLogSeverity.Trace);
return(new FilteredLogger(factory.CreateLogger(), filter.Apply));
})
)
// wrapping the logger with a try-catch
// when an error is caused by a log, that error is logged instead
.Decorate <ILoggerFactory>(factory =>
LoggerFactory(() => new FailsafeLogger(factory.CreateLogger()))
)
// registering the loggers
.AddSingleton(provider =>
// provide a proxy layer for loggers so that loggers that were created earlier,
// will still use the appropriate logger for the current execution context
new ProxyCachingLoggerFactory(
LoggerFactory(() =>
{
// create a sequenceId, a unique identifier to correlate logs within the same execution
var sequenceId = Guid.NewGuid();
return(new ScopedSequenceLogger(
// create a source to identify where logs came from once they are collected in a central database
new ScopedSourceLogger(
// change type of pipeline
new OutputLogger(
// format structured logs as json
JsonLogOutput.CreateLogOutputStream(
// write json logs to the console
new ConsoleOutputStream()
)
),
source => source.Plus("SystemServiceProvider-Example")
),
guid => sequenceId
));
})
)
)
// allowing services to ask for an ILogger
.AddScoped(provider =>
provider.GetRequiredService <ILoggerFactory>()
.CreateLogger())
// providing other services
.AddTransient <ExampleProgram>()
.AddTransient <ExampleTransientService>()
.AddTransient <ExampleSingletonService>()
.BuildServiceProvider();