Summary

Fixes #2907 LMCache emits an empty error message when enable_controller=True but required config fields are missing.

Root Cause

Two interacting bugs:

1. Missing validation in _validate_config(): When enable_controller=True, no validation was performed for required controller fields (lmcache_instance_id, controller_pull_url, controller_reply_url, lmcache_worker_ports). Config silently passed with None values, causing a runtime failure deep in the worker init.

2. Bare assert statements in worker.py: Checks like assert config.controller_pull_url is not None raise AssertionError with an empty string when they fail, resulting in the confusing ": ." in the error log.

Changes

lmcache/v1/config.py

• Added if self.enable_controller: validation block in _validate_config()
• Each required field is individually checked with raise ValueError(...) and a clear message
• lmcache_worker_ports also rejects empty lists (not just None)
• Follows the existing pattern used for enable_p2p validation in the same method

lmcache/v1/cache_controller/worker.py

• Replaced 4 bare assert statements with explicit if/raise ValueError checks
• Port-count checks now include actual vs expected values in f-strings
• Uses ValueError instead of assert to ensure validation is not bypassed by python -O

tests/v1/test_config.py

• Added 7 test cases covering all controller validation paths:
  • Each required field missing individually ValueError
  • Empty lmcache_worker_ports list ValueError
  • Valid config with all fields no error
  • enable_controller=False with missing fields no error

Before / After

Before:

LMCache ERROR: Failed to initialize LMCacheManager components: . System will operate in degraded mode (recompute).

After (at config creation time):

ValueError: controller_pull_url is required when enable_controller=True

Testing

• 7 new unit tests added and passing
• Zero impact on correctly-configured setups (if self.enable_controller: block is never entered when enable_controller=False)
• No existing tests broken