tree 95ff4d67ab4707d41a0ddad1e801c55cf8bf33c7
parent 6cad861fbb3dbb646d190b7a5efc2fe982ea3aa8
author Sean McCullough <banksean@gmail.com> 1748825744 +0000
committer Sean McCullough <banksean@gmail.com> 1748827755 -0700

loop: add periodic port monitoring to container processes

Partial fix for issue #47

Implement periodic port monitoring functionality that runs ss every 5 seconds
to detect changes in container listening ports, providing visibility into port
usage changes during sketch agent execution.

Problem Analysis:
Container processes need visibility into port changes that occur during
agent execution. Without monitoring, it's difficult to detect when services
start or stop listening on ports, which can be crucial for debugging
and understanding application behavior.

Implementation:
Added comprehensive port monitoring system to Agent struct:

1. Port Monitoring Infrastructure:
   - Added portMonitorMu mutex and lastPorts field to Agent struct
   - Created startPortMonitoring() method that launches background goroutine
   - Uses time.Ticker with 5-second intervals for periodic checks
   - Only activates when running in container mode (IsInContainer() check)

2. Port Detection Logic:
   - updatePortState() executes ss -lntu to get listening ports
   - Compares current port state with previous state for change detection
   - Thread-safe port state updates using dedicated mutex

3. Port Parsing and Comparison:
   - isSSOutput() automatically detects command output format
   - Extracts protocol and local address from port listings
   - Returns map[string]bool for efficient port comparison

4. Change Detection and Logging:
   - logPortDifferences() identifies newly opened and closed ports
   - Structured logging with slog for port changes
   - Separate log entries for new ports and closed ports
   - Non-critical operation - errors don't interrupt agent execution

Technical Details:
- Background goroutine lifecycle tied to agent context cancellation
- Handles IPv4/IPv6 address formats correctly
- Only monitors LISTEN state ports, ignores other connection states
- 5-second polling interval balances responsiveness with resource usage

Testing:
- Added comprehensive test coverage for port parsing functions
- Verifies port difference detection logic
- All existing loop package tests continue to pass
- Integration test confirms no regressions in agent functionality

Integration:
- Port monitoring starts automatically in Agent.Loop() method
- Only enabled for container execution mode
- Uses same context pattern as existing background tasks
- Follows established logging and error handling patterns

This enhancement provides real-time visibility into container port
changes without affecting core agent functionality or performance.

Benefits:
- Real-time port change detection for debugging
- Thread-safe implementation with proper resource cleanup
- Comprehensive test coverage ensures reliability

Co-Authored-By: sketch <hello@sketch.dev>
Change-ID: s9bd1b1bd0b518b2bk