Microsoft.Extensions.Logging.EventSource
A logger that writes messages to EventSource instance.
On Windows platforms EventSource will deliver messages using Event Tracing for Windows (ETW) events.
On Linux EventSource will use LTTng (http://lttng.org) to deliver messages.
ActivityScope is just a IDisposable that knows how to send the ActivityStop event when it is
desposed. It is part of the BeginScope() support.
'serializes' a given exception into an ExceptionInfo (that EventSource knows how to serialize)
The exception to get information for.
ExceptionInfo object represending a .NET Exception
ETW does not support a concept of a null value. So we use an un-initialized object if there is no exception in the event data.
Converts an ILogger state object into a set of key-value pairs (That can be send to a EventSource)
The provider for the .
Creates an instance of .
The logging event source.
Represents information about exceptions that is captured by EventSourceLogger
Bridges all ILogger-based logging to EventSource/EventListener logging.
To turn this logging on, you enable the EventSource called Microsoft-Extensions-Logging. When you enable the EventSource, the EventLevel you set is translated in to the level associated with the ILogger (thus Debug = verbose, Informational = Informational, Critical == Critical). This allows you to filter by event level in a straightforward way.
For finer control, you can specify an EventSource argument called FilterSpecs. The FilterSpecs argument is a semicolon-separated list of specifications. Where each specification is:
SPEC = // Empty spec, same as *.
| NAME // Named spec. Uses the default level.
| NAME : LEVEL // Specifies level for a particular logger (can have a * suffix).
When "UseAppFilters" is specified in the FilterSpecs, it avoids disabling all categories, which happens by default otherwise.
Name is the name of an (case matters), and can end with *, which acts as a wildcard. For example, Net* will match any loggers that start with 'Net'.
LEVEL is a number or a string (0=Trace, 1=Debug, 2=Information, 3=Warning, 4=Error, Critical=5). This specifies the level for the associated pattern. If the number isn't specified (first form of the specification), it's the default level for the EventSource.
The first match is used if a particular name matches more than one pattern.
In addition to the level and FilterSpecs argument, you can also set EventSource keywords:
* Keywords.Message - Event contains data in parsed form.
* Keywords.JsonMessage - Event contains data in parsed form but as a JSON blob (not broken up by argument).
* Keywords.FormattedMessage - Event contains data formatted as a string.
It's expected that only one of these keywords is turned on at a time, but you can turn them all on (and get
the same data logged three different ways).
This example shows how to use an EventListener to get ILogging information.
class MyEventListener : EventListener {
protected override void OnEventSourceCreated(EventSource eventSource) {
if (eventSource.Name == "Microsoft-Extensions-Logging") {
// Initialize a dictionary of arguments to pass to the EventSource.
// Turn on loggers matching App* to Information; everything else (*) is the default level (which is EventLevel.Error).
var args = new Dictionary<string, string>() { { "FilterSpecs", "App*:Information;*" } };
// Set the default level (verbosity) to Error, and only ask for the formatted messages in this case.
EnableEvents(eventSource, EventLevel.Error, LoggingEventSource.Keywords.FormattedMessage, args);
}
}
protected override void OnEventWritten(EventWrittenEventArgs eventData) {
// Look for the formatted message event, which has the following argument layout (as defined in the LoggingEventSource):
// FormattedMessage(LogLevel Level, int FactoryID, string LoggerName, string EventId, string FormattedMessage);
if (eventData.EventName == "FormattedMessage")
Console.WriteLine($"Logger {eventData.Payload[2]}: {eventData.Payload[4]}");
}
}
Defines the different ways data can be formatted in an event.
Events about the LoggingEventSource itself (that is, they did not come from ILogger).
Turns on the 'Message' event when ILogger.Log() is called. Provides information in a programmatic (unformatted) way.
Turns on the 'FormatMessage' event when ILogger.Log() is called. Provides the formatted string version of the information.
Turns on the 'MessageJson' event when ILogger.Log() is called. Provides a JSON representation of the Arguments.
The one and only instance of the LoggingEventSource.
FormattedMessage() is called when ILogger.Log() is called. and the FormattedMessage keyword is active
This only gives you the human readable formatted message.
Message() is called when ILogger.Log() is called. and the Message keyword is active
This gives you the logged information in a programmatic format (arguments are key-value pairs)
ActivityStart is called when ILogger.BeginScope() is called
Set the filtering specification. null means turn off all loggers. Empty string is turn on all providers.
The filter specification to set.
Given a set of specifications Pat1:Level1;Pat1;Level2 ... Where
Pat is a string pattern (a logger Name with a optional trailing wildcard * char)
and Level is a number 0 (Trace) through 5 (Critical).
The :Level can be omitted (thus Pat1;Pat2 ...) in which case the level is 1 (Debug).
A completely empty string act like * (all loggers set to Debug level).
The first specification that 'loggers' Name matches is used.
Parses the level specification (which should look like :N where n is a number 0 (Trace)
through 5 (Critical). It can also be an empty string (which means 1 (Debug) and ';' marks
the end of the specification. This specification should start at spec[curPos]
It returns the value in 'ret' and returns true if successful. If false is returned ret is left unchanged.
Extension methods for the class.
Adds a logger that writes messages to the instance.
The extension method argument.
The so that additional calls can be chained.
Adds a logger that writes messages to the instance.
The extension method argument.
The so that additional calls can be chained.
Scope provider that does nothing.
Returns a cached instance of .
An empty scope without any logic