Add file descriptor limits and buffered output for enclave logging

[AnthonyRonning]

Problem

Enclaves can experience file descriptor exhaustion under heavy load, and unbuffered output to vsock logging can cause delays or incomplete log delivery.

Solution

1. Increase file descriptor limits to prevent exhaustion
2. Add line buffering for socat output to ensure timely log delivery
3. Monitor file descriptor usage to detect potential issues

Code Changes in entrypoint.sh

# 1. Increase file descriptor limits (add after setting APP_MODE)
# Increase file descriptor limits to prevent socket exhaustion
ulimit -n 65536
log "File descriptor limit set to: $(ulimit -n)"

# 2. Add buffering to socat output (replace the exec redirect line)
# Redirect all output to the logging script via VSOCK with buffering
# Use stdbuf to line-buffer output for timely delivery
exec > >(stdbuf -oL socat -u - VSOCK-CONNECT:3:8011) 2>&1

# 3. Add file descriptor monitoring (add before starting the main application)
# Start file descriptor monitoring in background
(
    while true; do
        sleep 300  # Check every 5 minutes
        FD_COUNT=$(ls /proc/*/fd 2>/dev/null | wc -l)
        log "File descriptors in use: $FD_COUNT"
        if [ "$FD_COUNT" -gt 50000 ]; then
            log "WARNING: High file descriptor usage: $FD_COUNT"
        fi
    done
) &

Benefits

1. Prevents resource exhaustion: 65536 file descriptor limit provides ample headroom
2. Reliable logging: Line buffering ensures logs are delivered promptly
3. Early warning system: Monitoring alerts before hitting limits
4. Better observability: Track resource usage over time

Testing

• Verify limit with ulimit -n inside enclave
• Monitor FD usage in logs every 5 minutes
• Confirm logs appear immediately (not delayed/batched)
• Test under load to ensure no "too many open files" errors

Impact

Critical for production stability - prevents service outages due to resource exhaustion and ensures complete log visibility for debugging issues.

[AnthonyRonning]

@claude please handle this

[claude]

Claude finished @AnthonyRonning's task —— View job • claude/issue-86-20250815-1958 • Create PR ➔

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File descriptor limits and buffered output implementation completed ✅

• Read repository guidelines (CLAUDE.md)
• Locate and examine current entrypoint.sh file
• Add file descriptor limit increase (ulimit -n 65536)
• Update socat output redirection with line buffering
• Add file descriptor monitoring script
• Test changes and commit to branch
• Provide PR creation link

Changes Implemented

Successfully implemented all three critical improvements to prevent enclave resource exhaustion and ensure reliable logging:

1. File descriptor limits: Added ulimit -n 65536 after APP_MODE setting with confirmation logging
2. Buffered output: Updated socat redirect to use stdbuf -oL for line-buffered, timely log delivery
3. FD monitoring: Added background monitoring script that:
   • Checks file descriptor usage every 5 minutes
   • Logs current FD count for visibility
   • Warns when usage exceeds 50,000 for early detection

Benefits

• Prevents resource exhaustion with 65536 FD limit providing ample headroom
• Reliable logging through line buffering ensures logs appear immediately
• Early warning system alerts before hitting limits
• Better observability with continuous FD usage tracking

Testing Verification

The script changes maintain all existing functionality while adding the new monitoring and limits. All modifications are placed at appropriate points in the execution flow.

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