How can I get the message queue length of a GenServer? I have tried def handle_call({:add,number},_from, state) do {_,num}=Process.info(self(), :message_queue_len) IO.inspect num {:reply,reply state} end but getting 0.

How are you sending messages to that process? I notice that you’re doing this in a handle_call which is synchronous. So, if you only have one process doing a GenServer.call to this process it’ll block until it gets a response. That means, you’ll never have a queue length, because this handle_call i…

Try something like this to test: 1..100 |> Task.async_stream(fn _ -> # Thing that calls your process end) |> Stream.run()

If you want to observe the size and not assert on it, :observer is specifically for this. :observer.start() will open the Observer WX GUI, go to the processes tab and you can sort on the MsgQ column. Right-clicking will allow you to get a dump of the current messages, but the Processes tab will re…

@KronicDeth thanks…but I want the GenServer to take actions based on the queue length.Imagine 3 GenServers spun up by a DynamicSupervisor and they are all sending messages to each other but they don’t accept new messages if the message count is over 50 in their respective queues and send a reply bac…

Sounds like you want to control the ingestion of data in your system. If that’s the case, rather than fiddling with the queue length, I’d suggest taking a look at GenStage.

[image] elixirnewbie: but I want the GenServer to take actions based on the queue length That is irrelevant given that the process can only control removal of messages from the mailbox and nothing else - i.e. a process can’t stop accepting messages; it can only stop accepting work which would…

Thanks @stefanchrobot @peerreynders @peerreynders basically I want to know the total remaining messages in the mailbox that haven’t been processed

A better way is to use ETS to track the queue length, then you can tell that the queue is full before messaging the process. See “Bounded Queues” under Handling Overload Edit: just realized you might be beginning with Elixir, so this is probably overkill. What kind of work do your processes do? The…

[image] elixirnewbie: basically I want to know the total remaining messages in the mailbox that haven’t been processed You already know the answer - you just aren’t creating the right conditions to see the effects. defmodule Demo do defp do_it(state) do {_, num} = Process.info(self(),…

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Message queue length of a GenServer

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boilercoding May 30, 2022, 5:05pm 21

Thanks a lot @msimonborg it makes more sense now.