Hi there,

Is there a way to trace, in any way, when a message arrives in the mailbox of a GenServer? Note, I am not refering to the moment when a message is actually handled (taken out of the mailbox). I am specifically refering to the moment when a message arrives in the mailbox (and might sit there for quite some time before it is actually handled).

I’ve looked at the dbg module, specifically into tracing receive in a specified Process. However, I am not sure this is the correct approach and I only end up with either very generic or totally unreadable trace messages.

For example:

{:"$gen_cast", {:push, :hello}}
{#Reference<0.4094062663.2986868739.152886>, {:ok, {1678, 384779, 246000}}}
{#Reference<0.4094062663.2986868740.153344>, {:ok, <<4, 0, 0, 0, 1, 127, 0, 0, 1, 0, 0, 0, 1, 65, 114, 110, 111, 0>>}}     
{[:alias | #Reference<0.4094062663.2986934276.153347>], {:ok, 52087622}}
{[:alias | #Reference<0.4094062663.2986934276.153348>], {:error, :no_socket, #PID<0.271.0>}}
{#Reference<0.4094062663.2986868740.153350>, {:ok, <<4, 0, 0, 0, 1, 127, 0, 0, 1, 0, 0, 0, 1, 65, 114, 110, 111, 0>>}}   

In the end, whenever a message arrives in the mailbox of a GenServer I would like to be able to log it somewhere, or even send an API call somewhere. As such, I would definetly need information about the message that arrived itself (i.e. content), as well as where it arrived (i.e. PID) and if possible also the type (i.e. cast/call).

It might be that this is impossible due to the nature of an actor (Process), in that case it would be nice to have this confirmed such that I do not search needlessly for a non-existent solution.

module