I haven't studied this carefully, but this seems like an important improvement that needs a test?

I spent some time with this and stepped through and it all seems good to me.

The one TODO if you think it's appropriate is to see if a test can be added. If you think the xhgui stuff is testing it adequately, that's OK.

Below is Claude's opinion. Seems all fine.

Overview

This PR addresses router health issues with optional services by improving Traefik entrypoint port discovery and optimizing YAML file writes. The changes fix the issue where the router wasn't becoming healthy due to missing entrypoints for services defined in project configurations but not yet running.

Key Changes

1. Enhanced Port Discovery (pkg/ddevapp/router.go:341-418)

Strengths:

• Comprehensive port detection: Now reads from both project configuration files AND running containers, fixing the core issue where optional services weren't detected
• Cleaner code structure: Extracted processExposePorts() helper function for better maintainability
• Robust error handling: Continues processing other projects if one fails to read
• Better documentation: Clear comments explaining the port mapping logic

Technical details:

• Calls ReadDockerComposeYAML() for all active projects to extract HTTP_EXPOSE/HTTPS_EXPOSE from service environments
• Properly handles pointer dereferencing for environment variables
• Maintains existing behavior for running containers while adding configuration-based discovery

2. YAML Write Optimization (pkg/ddevapp/compose_yaml.go:19-132)

Strengths:

• Performance improvement: Avoids unnecessary file writes when content is unchanged using bytes.Equal()
• Maintains atomicity: Still uses proper file creation/closing patterns
• Added ReadDockerComposeYAML(): New function to read compose files, supporting the router port discovery

Technical details:

• Implements content comparison before writing both base and full YAML files
• Uses bytes.Equal() instead of string comparison for better performance
• Preserves existing error handling and file closing patterns

3. File Utility Enhancement (pkg/fileutil/embed.go:46-49)

Strengths:

• Consistency: Uses same bytes.Equal() optimization pattern
• Minor but effective: Removes unnecessary string conversion

Code Quality Assessment

Positive aspects:

• ✅ Passes all static analysis (make staticrequired)
• ✅ Follows existing code patterns and conventions
• ✅ Proper error handling throughout
• ✅ Clear, descriptive function and variable names
• ✅ Good separation of concerns with the new helper function

Areas that could be improved:

• The determineRouterPorts() function is getting quite long (70+ lines). Consider splitting the config-based and container-based logic into separate functions
• Could benefit from unit tests for processExposePorts() function
• The error handling for ReadDockerComposeYAML() uses util.Warning() but continues - consider if this is the right approach

Testing Considerations

The PR description provides good manual testing instructions. However, automated tests would strengthen confidence:

Suggested tests:

• Unit test for processExposePorts() with various port formats
• Integration test verifying port discovery from stopped services
• Test for YAML write optimization (verify files aren't rewritten when unchanged)

Impact Analysis

Positive impacts:

• ✅ Fixes router health issues with optional services (addresses ddev/ddev-mongo#24)
• ✅ Reduces unnecessary disk I/O through YAML write optimization
• ✅ More reliable port discovery for Traefik configuration
• ✅ Better user experience with optional add-ons

Risk assessment:

• 🟡 Low risk: Changes are primarily additive, maintaining backward compatibility
• 🟡 Performance: Additional file reads for all active projects during router startup (acceptable trade-off)

Recommendation

✅ APPROVE with minor suggestions

This is a well-implemented fix that solves a real problem. The code quality is good, follows established patterns, and the optimizations are beneficial. The approach of reading project configurations in addition to running containers is the right solution for detecting optional services.

Minor suggestions for follow-up:

1. Consider splitting determineRouterPorts() for better maintainability
2. Add unit tests for the new processExposePorts() function
3. Consider caching the project configuration reads if this becomes a performance concern

The PR successfully addresses the core issue and includes valuable optimizations as a bonus.

It's still great, thanks, and thanks for understanding, studying, and solving this, and caring for ddev-mongo.

I wonder if this means that we could now start/restart traefik before everything else is up and ready, which might slightly improve user experience. (Related idea: Most people in most situations don't really need to wait for everything to be fully ready. We might want to give them an out like "press return to get to work")