You can enable debug logs in Cloudprober by setting the --debug_log flag. However, it may produce a lot of logs, making it difficult to find what you're looking for. To fix that problem, Cloudprober comes with another flag: --debug_logname_regex. This flag lets you filter logs by log attributes -- in most cases it's sufficient to filter by probe name or surfacer name. Example invocation:

# Show debug logs only for probe named dns_probe
cloudprober --config_file=/cfg/cloudprober.cfg --debug_log --debug_logname_regex=dns_probe

# Show debug logs for prometheus surfacer
cloudprober --config_file=/cfg/cloudprober.cfg --debug_log --debug_logname_regex=prometheus

# Show global debug logs, log associated with overall cloudprober independent of any component
cloudprober --config_file=/cfg/cloudprober.cfg --debug_log --debug_logname_regex=global

Caution: Debug logs may contain sensitive information, be careful while enabling them.