Hi there, I have a phoenix controller from which I spawn a Task with Task.Supervisor.start_child for some async processing. I’d like to propagate all the metadata I have in the logger of the parent process to the task logger, in order to have a continuous tracing; is there a better/standard way of…

Not really. All approaches will effectively need the same approach. However I would do it like that: metadata = :logger.get_process_metadata() Task.Supervisor.start_child(fn -> :logger.set_process_metadata(metadata) my_task() end) So the my_task/0 will not need to know anything about logger m…

I recently observed a strange error in some code using this pattern: ** (ArgumentError) argument error logger.erl:621 :logger.set_process_metadata(:undefined) I’m not familiar with Erlang but looking at the docs, it looks like it might not be technically safe because get_process_metadata can retur…

I mean it returns that if no process meta data is set, so if you always make sure to set it you should be save - which of course is more complex in a bigger data. As an alternative you can use Logger.metadata/0 - which seems to return [] in this case and hence shouldn’t break. iex(1)> :logger.get_…

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Propagate logger metadata in spawned task

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csuriano23 September 16, 2021, 9:00am 3

Thanks for the feedback!