Serilog Dual Datadog Sinks - .NET 6

A minimal .NET 6 console application demonstrating dual Datadog log sinks configuration with Serilog, sending logs simultaneously to two different Datadog regions (US and EU).

Features

✅ Dual Datadog sinks configured at the same level
✅ US region sink (https://http-intake.logs.datadoghq.com)
✅ EU region sink (https://http-intake.logs.datadoghq.eu)
✅ Different log levels per sink (Information vs Warning)
✅ Custom tags per region
✅ Console output for verification
✅ Configuration-based setup via appsettings.json
✅ Built-in diagnostic logging with SelfLog
✅ File-based sink simulation for testing without API keys
✅ Real-time sink status verification

Prerequisites

.NET 6 SDK or higher
Valid Datadog API keys for US and/or EU regions
Network access to Datadog (port 443 for HTTPS)

Getting Started

1. Clone or Download

cd SerilogDatadogDualSinks-net6

2. Configure API Keys

Edit appsettings.json and replace the placeholder API keys:

REPLACE_WITH_API_KEY_US → Your Datadog US API key
REPLACE_WITH_API_KEY_EU → Your Datadog EU API key

Note: Each Datadog site requires its own API key. Get your keys from:

US: Datadog US Dashboard
EU: Datadog EU Dashboard

3. Run the Application

dotnet restore
dotnet run

Configuration Overview

The application uses five sinks configured simultaneously:

Sink	Type	Region/Purpose	URL/Path	Min Level	Tags
Console	Console	Display	-	All	-
File US	File	Simulate US	`logs/simulated-datadog-us-*.log`	`Information`	-
File EU	File	Simulate EU	`logs/simulated-datadog-eu-*.log`	`Warning`	-
Datadog US	Datadog	United States	`https://http-intake.logs.datadoghq.com`	`Information`	`env:dev`, `region:us`
Datadog EU	Datadog	Europe	`https://http-intake.logs.datadoghq.eu`	`Warning`	`env:dev`, `region:eu`

Key Differences Between Datadog Sinks

US Sink: Captures logs from Information level and above
EU Sink: Captures logs from Warning level and above (more restrictive)

Simulation Mode

The file sinks allow you to test the behavior without valid Datadog API keys:

simulated-datadog-us-*.log - Shows what would be sent to US region
simulated-datadog-eu-*.log - Shows what would be sent to EU region

Sample Output

Successful Execution

=================================================
SERILOG CONFIGURATION LOADED
=================================================

✓ Sink #1: Console

✓ Sink #2: File

✓ Sink #3: File

✓ Sink #4: DatadogLogs
  - Service: sample-app
  - URL: https://http-intake.logs.datadoghq.com
  - Min Level: Information
  - API Key: ⚠️  NOT CONFIGURED
  - Tags: env:dev, region:us

✓ Sink #5: DatadogLogs
  - Service: sample-app
  - URL: https://http-intake.logs.datadoghq.eu
  - Min Level: Warning
  - API Key: ⚠️  NOT CONFIGURED
  - Tags: env:dev, region:eu

=================================================
Total sinks loaded: 5
=================================================
💡 Tip: If API keys are valid, logs will appear in Datadog within ~30 seconds
🔍 Watch for RED messages below - they indicate sink errors

[17:32:42 INF] Application started
[17:32:42 WRN] This warning should go to both Datadog sinks
[17:32:42 INF] Processing item 0
[17:32:42 INF] Processing item 1
[17:32:42 INF] Processing item 2
[17:32:42 ERR] An error occurred while processing
[17:32:42 INF] Application finished successfully

⏳ Flushing logs to all sinks (this may take a few seconds)...
✅ All logs flushed successfully
📄 Check 'serilog-diagnostics.log' for any internal errors

Diagnostic Messages

When API keys are invalid or not configured, you'll see diagnostic messages in RED:

[SERILOG INTERNAL] Could not send payload to Datadog: [Forbidden] Forbidden

This is EXPECTED and confirms that:

✅ Sinks are loaded and working
✅ Logs are properly formatted
✅ HTTP requests are being made to Datadog
❌ Authentication failed (need valid API keys)

Verification Files

After running, check these files to verify behavior:

logs/simulated-datadog-us-YYYYMMDD.log - US region simulation (Information+)
logs/simulated-datadog-eu-YYYYMMDD.log - EU region simulation (Warning+)
serilog-diagnostics.log - Serilog internal errors (if any)

Project Structure

SerilogDatadogDualSinks-net6/
├── Program.cs                              # Main application
├── appsettings.json                        # Serilog & Datadog configuration
├── SerilogDatadogDualSinks-net6.csproj     # Project file
└── README.md                               # This file

Dependencies

Serilog (2.10.0) - Core logging library
Serilog.Settings.Configuration (3.3.0) - Configuration-based setup
Serilog.Sinks.Console (4.0.1) - Console output
Serilog.Sinks.File (5.0.0) - File output for simulation
Serilog.Sinks.Datadog.Logs (0.5.2) - Datadog integration
Serilog.Expressions (3.4.1) - Advanced filtering
Microsoft.Extensions.Configuration.Json (6.0.0) - JSON configuration
Microsoft.Extensions.Configuration.EnvironmentVariables (6.0.1) - Environment variables

Advanced Configuration

Using TCP Instead of HTTPS

To use TCP protocol instead of HTTPS, modify appsettings.json:

"configuration": {
  "url": "intake.logs.datadoghq.com",
  "port": 10516,
  "useSSL": true,
  "useTCP": true
}

Customizing Tags and Service Name

Adjust the following fields in appsettings.json:

"service": "your-app-name",
"tags": ["env:production", "region:us", "version:1.0.0"]

Adjusting Queue and Batch Settings

Control buffering behavior:

"queueLimit": 100000,
"batchSizeLimit": 1000

Verification & Testing

Test Without API Keys

The application includes simulation sinks that write to files. This allows you to verify the behavior without Datadog credentials:

dotnet run

Then check:

# View US sink simulation (Information+)
cat logs/simulated-datadog-us-*.log

# View EU sink simulation (Warning+ only)
cat logs/simulated-datadog-eu-*.log

# Check for internal errors
cat serilog-diagnostics.log

Verify Sinks Are Working

Look for these indicators:

✅ Working correctly:

Console shows ✅ Configured for API keys (if set) or ⚠️ NOT CONFIGURED
No RED messages during execution
serilog-diagnostics.log is empty or doesn't exist
Simulation files contain expected logs

❌ Issues detected:

RED [SERILOG INTERNAL] messages in console
serilog-diagnostics.log contains errors
Simulation files are missing or empty

Common Diagnostic Messages

Message	Meaning	Action
`[Forbidden] Forbidden`	Invalid API key	Replace placeholder with real API key
`An invalid request URI was provided`	Incorrect URL format	Ensure URL starts with `https://`
`Could not send payload to Datadog`	Network/auth issue	Check API key and network connectivity
No RED messages	Everything working	Logs are being sent successfully

Troubleshooting

Logs Not Appearing in Datadog

✅ Verify API keys are correct and not placeholders
✅ Check serilog-diagnostics.log for errors
✅ Verify simulation files show expected logs
✅ Check network connectivity to Datadog endpoints
✅ Ensure log level meets the sink's restrictedToMinimumLevel
✅ Wait ~30 seconds for ingestion (Datadog has slight delays)

Simulation Files Empty

If simulation files in logs/ are empty:

Check file permissions in the project directory
Verify Serilog.Sinks.File package is installed
Look for errors in serilog-diagnostics.log

RED Messages in Console

This is expected when:

Using placeholder API keys (REPLACE_WITH_API_KEY_*)
Testing without real credentials

This is NOT expected when:

Using valid API keys
URLs are correctly formatted

Build Warnings

If you see .NET version compatibility warnings, consider upgrading to .NET 8 or suppress warnings by adding to .csproj:

<SuppressTfmSupportBuildWarnings>true</SuppressTfmSupportBuildWarnings>

License

This is a sample project for demonstration purposes.

How It Works

Diagnostic Logging

The application uses Serilog.Debugging.SelfLog to capture internal errors:

SelfLog.Enable(msg =>
{
    Console.ForegroundColor = ConsoleColor.Red;
    Console.WriteLine($"[SERILOG INTERNAL] {msg}");
    Console.ResetColor();
});

This shows in real-time if sinks encounter issues like:

Network failures
Authentication errors
Configuration problems
Serialization issues

Sink Verification

The app displays configuration details on startup:

Sink type (Console, File, DatadogLogs)
Service name and URL
Minimum log level
API key status (configured or not)
Tags

This confirms sinks are loaded before any logging occurs.

Name		Name	Last commit message	Last commit date
Latest commit History 4 Commits
.gitignore		.gitignore
Program.cs		Program.cs
README.md		README.md
SerilogDatadogDualSinks-net6.csproj		SerilogDatadogDualSinks-net6.csproj
SerilogDatadogDualSinks-net6.sln		SerilogDatadogDualSinks-net6.sln
appsettings.json		appsettings.json

Folders and files

Latest commit

History

Repository files navigation

Serilog Dual Datadog Sinks - .NET 6

Features

Prerequisites

Getting Started

1. Clone or Download

2. Configure API Keys

3. Run the Application

Configuration Overview

Key Differences Between Datadog Sinks

Simulation Mode

Sample Output

Successful Execution

Diagnostic Messages

Verification Files

Project Structure

Dependencies

Advanced Configuration

Using TCP Instead of HTTPS

Customizing Tags and Service Name

Adjusting Queue and Batch Settings

Verification & Testing

Test Without API Keys

Verify Sinks Are Working

Common Diagnostic Messages

Troubleshooting

Logs Not Appearing in Datadog

Simulation Files Empty

RED Messages in Console

Build Warnings

License

How It Works

Diagnostic Logging

Sink Verification

Resources

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