Default logging we ship will incorrectly print "?:?" for "%F:%L" pattern due to includeCallerData being false by default no appender

We specify the logging pattern as "%-5level [%thread] %date

%F:%L - %msg%n".

%F:%L is intended to print the Filename:Line Number. For performance reasons logback (like log4j2) disables tracking line numbers as it requires the entire stack to be materialized every time.

This causes logs to look like:
WARN [main] 2017-03-09 13:27:11,272 ?:? - Protocol Version 5/v5-beta not supported by java driver
INFO [main] 2017-03-09 13:27:11,813 ?:? - No commitlog files found; skipping replay
INFO [main] 2017-03-09 13:27:12,477 ?:? - Initialized prepared statement caches with 14 MB
INFO [main] 2017-03-09 13:27:12,727 ?:? - Initializing system.IndexInfo

When instead you'd expect something like:
INFO [main] 2017-03-09 13:23:44,204 ColumnFamilyStore.java:419 - Initializing system.available_ranges
INFO [main] 2017-03-09 13:23:44,210 ColumnFamilyStore.java:419 - Initializing system.transferred_ranges
INFO [main] 2017-03-09 13:23:44,215 ColumnFamilyStore.java:419 - Initializing system.views_builds_in_progress

The fix is to add "<includeCallerData>true</includeCallerData>" to the appender config to enable the line number and stack tracing.