SyslogLogging

SyslogLogging is a C# logging library for syslog, console, and file destinations. It supports synchronous and asynchronous logging, structured log entries, Microsoft.Extensions.Logging integration, and file retention management.

Current release: 2.1.0

Target builds:

• .NET Standard 2.0
• .NET Standard 2.1
• .NET Framework 4.6.2
• .NET Framework 4.8
• .NET 8.0
• .NET 10.0

Highlights

• RFC 3164 syslog output
• Console and file logging in the same logger
• Structured logging with LogEntry
• Fluent structured logging builder
• Microsoft.Extensions.Logging provider and DI registration
• Configurable header format tokens including {app}, {pid}, {source}, and {correlation}
• Configurable exception severity
• Automatic retention cleanup for dated log files
• Shared Touchstone test coverage exposed through CLI, xUnit, and NUnit runners

What's New in 2.1.0

• Added LoggingSettings.ApplicationName so callers can explicitly control the {app} header token without changing the existing logging API.
• Changed {app} fallback resolution to use Assembly.GetEntryAssembly()?.GetName().Name before falling back to the current process name.
• Fixed .Exception() and .ExceptionAsync() so they honor LoggingSettings.ExceptionSeverity.
• Fixed concurrent async file logging so writes are serialized correctly under load.
• Migrated tests to Touchstone shared suites with CLI, xUnit, and NUnit runners on net8.0 and net10.0.

Installation

dotnet add package SyslogLogging

Quick Start

Simple Logging

using SyslogLogging;

LoggingModule log = new LoggingModule();
await log.InfoAsync("Hello, world!");

Syslog Logging

using SyslogLogging;

LoggingModule log = new LoggingModule("mysyslogserver", 514);
await log.WarnAsync("Rate limit exceeded");

File Logging

using SyslogLogging;

LoggingModule log = new LoggingModule("./logs/app.log", FileLoggingMode.SingleLogFile);
await log.InfoAsync("File-only message");

Structured Logging

LogEntry

LogEntry entry = new LogEntry(Severity.Error, "Payment processing failed")
    .WithProperty("OrderId", orderId)
    .WithProperty("Amount", amount)
    .WithProperty("Currency", "USD")
    .WithCorrelationId(correlationId)
    .WithSource("PaymentService")
    .WithException(exception);

await log.LogEntryAsync(entry);

Fluent Builder

await log.BeginStructuredLog(Severity.Info, "User login")
    .WithProperty("UserId", userId)
    .WithProperty("IpAddress", ipAddress)
    .WithCorrelationId(correlationId)
    .WriteAsync();

Microsoft.Extensions.Logging Integration

services.AddLogging(builder =>
{
    builder.AddSyslog("syslogserver", 514);
});

Multiple syslog targets are also supported:

services.AddLogging(builder =>
{
    builder.AddSyslog(new List<SyslogServer>
    {
        new SyslogServer("primary-log", 514),
        new SyslogServer("backup-log", 514)
    }, enableConsole: true);
});

Header Formatting

log.Settings.HeaderFormat = "{ts} {host}[{pid}] {sev} [T:{thread}] [{app}]";
log.Settings.ApplicationName = "MyService";
log.Settings.TimestampFormat = "yyyy-MM-dd HH:mm:ss.fff";
log.Settings.UseUtcTime = true;

Available header variables:

Variable	Description	Example
{ts}	Timestamp	2024-01-15 14:30:25.123
{host}	Machine name	web-server-01
{thread}	Thread ID	12
{sev}	Severity name	Info
{level}	Severity number	6
{pid}	Process ID	1234
{user}	Current username	john.doe
{app}	Application name	MyWebApp
{domain}	App domain	MyWebApp.exe
{cpu}	CPU core count	8
{mem}	Memory usage in MB	256
{uptime}	Process uptime	02:45:30
{correlation}	Correlation ID	abc-123-def
{source}	Log source	UserService

{app} resolves in this order:

1. log.Settings.ApplicationName
2. Assembly.GetEntryAssembly()?.GetName().Name
3. Current process name

File Retention

LoggingModule log = new LoggingModule("./logs/app.log", FileLoggingMode.FileWithDate, true);
LoggingSettings settings = log.Settings;
settings.LogRetentionDays = 30;
log.Settings = settings;

Retention cleanup only applies when using FileLoggingMode.FileWithDate. The cleanup timer removes files matching the dated filename pattern when they are older than the configured retention period.

Testing

Run the shared Touchstone suite through the CLI runner:

dotnet run --project src/Test.Automated/Test.Automated.csproj -f net10.0
dotnet run --project src/Test.Automated/Test.Automated.csproj -f net8.0

Run the same shared descriptors through xUnit and NUnit:

dotnet test src/Test.Xunit/Test.Xunit.csproj
dotnet test src/Test.Nunit/Test.Nunit.csproj

The shared suite covers:

• Constructor and settings validation
• Severity helpers
• Structured and fluent logging APIs
• Exception severity behavior
• File output and retention cleanup
• Message ordering and concurrency
• Syslog delivery and error handling
• Microsoft.Extensions.Logging integration

Related Project

The repository also includes SyslogServer, a simple utility application for receiving syslog traffic during development and testing.

Version History

See CHANGELOG.md for release details.

Help

File issues or feature requests at:

https://github.com/jchristn/LoggingModule/issues