New Logger in Erlang

https://ferd.ca/erlang-otp-21-s-new-logger.html

• OTP-21 -> new logging library in Erlang - logger
• an alternative and “result” of lager library
• STRUCTURE
  • you should not know the structure of logger to use it. But to extend - you should
  • logger exposes 3 types of components with well-defined interfaces
    • Log Filters
    • Log Handlers
    • Log Formatters
  • These elements are in config database (ETS -> cheap)
  • You want to log asap (move everything to another process).
  • For Erlang (preemptive concurrency) logger might be a bottleneck:

    

  • => we want to distribute this work as much as possible at the call-site
  • quick -> will not be noticeable

    

  • as logger-configuration is ready for concurrent reading -> easy to implement
• DATA FLOW
  • check level, get logger config
  • apply general filters, apply handlers (+filters +formatters)
  • skip logging on any level
  • disk logging - one process that handle a file descriptor
• GOOD LOGGING
  • log what you know/observe, not your deductions (ssl problems -> “your system is hacked”)
  • single way to produce logs -> auto dispatch to different storage based on content
  • structured logs (maps of maps -> handler to flatten or json them)
• MORE
  • distributed tracing work nicely with the logger
  • metrics from log - too
  • which fields logs should contain (table)