Envoy has a built-in admin server that has a large amount of useful tools for debugging. The full abilities of this interface can be found in the docs, but some highlights are given here.
Log Levels
Envoy has the ability to set different log levels for different components of the running system. To see how they're all currently set:
NOTE all examples below assume the admin interface is started on port 8001 (the default option). Adjust according to your configuration.