Add HTTP debug logging for Docker API calls

[cnuss]

Summary

This PR adds comprehensive HTTP debug logging for Docker API calls to aid in troubleshooting and debugging issues with the Docker client integration.

Changes

• Debug Transport Layer: Implemented a new HTTP transport wrapper (wrappedTransport) that intercepts Docker API requests and responses
• Configurable Logging Levels:
  • Info level (default): Standard logging, no Docker API call details
  • Debug level: Logs request method, endpoint, and response status
  • Trace level: Additionally logs full request and response bodies for detailed inspection
• Modified getDockerClient: Updated to automatically apply the debug transport when log level is set to debug or higher
• Updated CLI Help: Enhanced --log-level flag description to list all available log levels (panic, fatal, error, warn, info, debug, trace) and indicate that 'debug' and 'trace' levels enable Docker API logging
• Comprehensive Test Coverage: Added extensive unit tests and integration tests for the new debug functionality

Example Output

Info Level (default)

INFO[0000] Starting cri-dockerd 0.3.0
INFO[0000] Connecting to docker on the Endpoint unix:///var/run/docker.sock

Debug Level

INFO[0000] Starting cri-dockerd 0.3.0
INFO[0000] Connecting to docker on the Endpoint unix:///var/run/docker.sock
DEBU[0001] (dockerapi) GET unix:///var/run/docker.sock/v1.43/version => 200 OK
DEBU[0001] (dockerapi) GET unix:///var/run/docker.sock/v1.43/info => 200 OK
DEBU[0002] (dockerapi) POST unix:///var/run/docker.sock/v1.43/containers/create => 201 Created
DEBU[0002] (dockerapi) POST unix:///var/run/docker.sock/v1.43/containers/abc123/start => 204 No Content

Trace Level

INFO[0000] Starting cri-dockerd 0.3.0
INFO[0000] Connecting to docker on the Endpoint unix:///var/run/docker.sock
TRAC[0001] (dockerapi) GET unix:///var/run/docker.sock/v1.43/version: (empty) => 200 OK {"Version":"24.0.7","ApiVersion":"1.43","MinAPIVersion":"1.12","GitCommit":"afdd53b"}
TRAC[0001] (dockerapi) GET unix:///var/run/docker.sock/v1.43/info: (empty) => 200 OK {"ID":"ABCD:1234","Containers":5,"Images":12,...}
TRAC[0002] (dockerapi) POST unix:///var/run/docker.sock/v1.43/containers/create: {"Image":"nginx","HostConfig":{"NetworkMode":"bridge"}} => 201 Created {"Id":"abc123def456","Warnings":[]}
TRAC[0002] (dockerapi) POST unix:///var/run/docker.sock/v1.43/containers/abc123/start: (empty) => 204 No Content (empty)

Files Changed

• cmd/server.go: Updated --log-level flag help text to document available levels and Docker API logging behavior
• libdocker/client.go: Modified to conditionally apply debug transport based on log level
• libdocker/debug.go: New file implementing the HTTP debug transport wrapper
• libdocker/debug_test.go: Comprehensive tests for debug transport functionality
• libdocker/client_test.go: Tests for getDockerClient with debug transport integration

Benefits

• Enables visibility into Docker API interactions without modifying application code
• Helps diagnose issues with container runtime operations
• Clear documentation in CLI help about available log levels and their effects
• Progressive detail: debug for high-level flow, trace for deep inspection
• Minimal performance overhead (only active when debug logging is enabled)
• No impact on production deployments (disabled by default)

Fixes #532

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🤖 Generated with Claude Code

[cnuss]

@athongsamai @awmirantis @smerkviladze could you take a look at this or assign some reviewers that could?

thanks!

[cnuss]

@chenyaooo i saw you recently dropped an update for this repo, could you 👀 this PR or ping someone who's able to?

thanks!

[cnuss]

@athongsamai @awmirantis @smerkviladze @chenyaooo any of you there?

[athongsamai]

@cnuss thanks for opening this PR.
Meanwhile we review your code change, could you make your commits the signed ones?
Refer to https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits.
The unsigned commit will not be accepted for merging.

[cnuss]

@athongsamai done! sorry i thought i had that turned on

[athongsamai]

LGTM, thanks for good PR!

[cnuss]

thanks @athongsamai ❤️ !! can you ping a 2nd reviewer to 👀 for me?

i might have a couple more PRs coming up as i'm trying to get a kubelet-in-docker working reliably.

[awmirantis]

LGTM