Implementing logging

Logging (sometimes also called tracing) is used to record information about a program's execution for debugging and testing purposes.

Developers, testers and support engineers often use logging and tracing techniques to identify software problems, for post-deployment debugging, monitoring live systems and auditing purposes.

Logging usually involves writing text messages to log files or sending data to monitoring applications. Advanced and modern logging tools also support logging of complex data structures, call stacks, threading behavior and also support real-time monitoring of applications over a network or on a local machine.

Serilog

Like many other libraries for .NET, Serilog provides diagnostic logging to files, the console, and elsewhere. It is easy to set up, has a clean API, and is portable between recent .NET platforms.

Unlike other logging libraries, Serilog is built with powerful structured event data in mind.

Text formatting

Serilog message templates are a simple DSL extending .NET format strings. Parameters can be named, and their values are serialized as properties on the event for incredible searching and sorting flexibility:

var position = new { Latitude = 25, Longitude = 134 };
var elapsedMs = 34;

Log.Information("Processed {@Position} in {Elapsed:000} ms.", position, elapsedMs);

This example records two properties, Position and Elapsed along with the log event. The properties captured in the example, in JSON format, would appear like:

{"Position": {"Latitude": 25, "Longitude": 134}, "Elapsed": 34}

Installation

Browse the Serilog tag on NuGet to see the available sinks, extensions and related third-party packages.

PM> Install-Package Serilog
PM> Install-Package Serilog.Sinks.Console

Configuration basics

Creating a logger

Loggers are created using a LoggerConfiguration object:

Log.Logger = new LoggerConfiguration().CreateLogger();
Log.Information("No one listens to me!");

Sinks

This example will use the console sink package, which pretty-prints log data, and the file sink package, which writes log events to a set of date-stamped text files.

Install-Package Serilog.Sinks.Console
Install-Package Serilog.Sinks.File

Sinks are configured using the WriteTo configuration object. Multiple sinks can be active at the same time. Adding additional sinks is a simple as chaining WriteTo blocks:

Log.Logger = new LoggerConfiguration()
    .WriteTo.Console()
    .WriteTo.File("log-.txt", rollingInterval: RollingInterval.Day)
    .CreateLogger();

Minimum level

Level	Usage
Verbose	Verbose is the noisiest level, rarely (if ever) enabled for a production app.
Debug	Debug is used for internal system events that are not necessarily observable from the outside, but useful when determining how something happened.
Information	Information events describe things happening in the system that correspond to its responsibilities and functions. Generally these are the observable actions the system can perform.
Warning	When service is degraded, endangered, or may be behaving outside of its expected parameters, Warning level events are used.
Error	When functionality is unavailable or expectations broken, an Error event is used.
Fatal	The most critical level, Fatal events demand immediate attention.

Writing Log Events

Log events are written to sinks using the Log static class, or the methods on an ILogger. These examples will use Log for syntactic brevity, but the same methods shown below are available also on the interface.