Exception Handling Path

Re-execute the pipeline to a fixed error path when an unhandled exception occurs. This renders a consistent error payload while keeping the original URL and method.

Full source

File: pwsh/tutorial/examples/18.1-ExceptionHandling-Path.ps1

#
# Sample: Exception Handling with Re-execution
# Demonstrates how to configure exception handling to re-execute the pipeline to a fixed error path.
# FileName: 18.1-ExceptionHandling-Path.ps1
#
param(
    [int]$Port = 5000,
    [IPAddress]$IPAddress = [IPAddress]::Loopback
)

Initialize-KrRoot -Path $PSScriptRoot
New-KrLogger | Set-KrLoggerLevel -Level Debug |
    Add-KrSinkConsole | Register-KrLogger -Name 'console' -SetAsDefault

# Create server and listener
New-KrServer -Name 'Exception Handling - ReExecute'
Add-KrEndpoint -Port $Port -IPAddress $IPAddress

# Configure exception handling to re-execute the pipeline at /error
Enable-KrExceptionHandling -ExceptionHandlingPath '/error'

# Finalize configuration
Enable-KrConfiguration

# A normal route
Add-KrMapRoute -Verbs Get -Pattern '/hello' -ScriptBlock {
    Write-KrJsonResponse @{ msg = 'Hello from /hello' } -StatusCode 200
}

# A route that throws to simulate an unhandled exception
Add-KrMapRoute -Verbs Get -Pattern '/throw' -ScriptBlock {
    throw [System.InvalidOperationException]::new('Boom! Something went wrong.')
}

# The error route that receives re-executed requests
Add-KrMapRoute -Verbs Get -Pattern '/error' -ScriptBlock {
    # Note: the request URL remains the original URL; this route handles the response content
    $path = $Context.Request.Path
    $method = $Context.Request.Method
    Write-KrJsonResponse @{ error = $true; message = 'Request re-executed to /error'; path = $path; method = $method } -StatusCode 500
}

Write-Host "Server starting on http://$($IPAddress):$Port" -ForegroundColor Green
Write-Host 'Try these URLs:' -ForegroundColor Yellow
Write-Host "  http://$($IPAddress):$Port/hello   - Happy path" -ForegroundColor Cyan
Write-Host "  http://$($IPAddress):$Port/throw   - Triggers exception, re-executes to /error" -ForegroundColor Cyan

Start-KrServer

Step-by-step

  1. Logging: Register console logger as default.
  2. Server: Create server and listen on loopback with a dynamic port.
  3. Exception handling: Enable Enable-KrExceptionHandling -ExceptionHandlingPath '/error'.
  4. Routes: Map /hello, /throw, and the handler route /error.
  5. Response: Return JSON from /error including path and method.
  6. Start: Apply configuration and start the server.

Try it 

# Happy path
curl -i http://127.0.0.1:5000/hello

# Trigger exception -> re-executes to /error
curl -i http://127.0.0.1:5000/throw

PowerShell equivalents:

Invoke-WebRequest -Uri http://127.0.0.1:5000/hello -UseBasicParsing | Select-Object StatusCode, Content
Invoke-WebRequest -Uri http://127.0.0.1:5000/throw -UseBasicParsing -SkipHttpErrorCheck | Select-Object StatusCode, Content

Troubleshooting

  • Getting a 404 on /error? Ensure the handler route is mapped and appears after enabling exception handling.
  • Seeing original path in JSON? That’s expected; the middleware re-executes to /error but preserves the original URL.

References

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