It’s important to realize that on GenServer.call/3 processing in the calling process blocks:
- an asynchronous message is
sent - the calling process enters a blocking receive with a timeout
- the calling process unblocks when either the timeout expires (failing the call) or when the awaited return message arrives
So the calling process isn’t doing anything between the sent and return message.
because we don’t know when the messages get lost in the air.
Sometimes it makes more sense to monitor the process responsible and using a timeout to determine whether the result will be available (in time). That way the casting process doesn’t block (but the process interaction protocol is more work).
