vrod
I am wondering for advice on how to monitor an application with many genservers doing long-running work. Often we want to know “how many messages are in the queue?” The process has a mailbox not a queue but this is the same idea : how can we see what our app is doing? I have seen GenStage.estimate_buffered_count/2 and I am wondering if that is the best way. There is a mix of genserver and genstage, so I thought maybe Process.info/1 could help with genservers, but I noticed that this function seems to require a pid and it will not work with a process name. Also I do not see the messages in the process info? Only message_queue_len?
Another idea was because we are using pubsub, maybe we could add subscribers that would count messages but that feels maybe smelly.
Thank you for suggestions!
Where Next?
Trending in Questions
Other Trending Topics
Latest on Elixir Forum
Sponsor Spotlight
Producing high quality Elixir screencasts since 2017.
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #library
- #deployment
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #elixirconf
- #channels
- #exunit
- #discussion
- #code-sync
- #podcasts
- #javascript
- #onsite
- #dialyzer
- #docker
- #authentication
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #ecto-query
- #ai
- #elixirconf-us
- #blog-post
- #elixir-ls
- #phoenix_html
- #iex
- #graphql
- #genstage
- #websockets
- #supervisor
- #advent-of-code
- #distillery
- #processes
- #api
- #forms
- #elixirconf-eu
- #metaprogramming
- #hex
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
Catch errors, track performance, monitor hosts and more.
Error tracking, logs, uptime, and Just Enough APM. Built for developers.
Elixir, Erlang & BEAM conferences from Code Sync - join us in 2026!
Practical resources that improve the lives of professional developers.
Producing high quality Elixir screencasts since 2017.
The deployment platform built for Elixir: PaaS ease, VPS control.
The team behind Membrane, Popcorn, LiveDebugger. Available for hire.
Courses that'll move you from confusion to "Aha, now I get it!"
Marked As Solved- Show Best Posts
- Show All (oldest first)
- Show All (newest first)
rvirding
A simple way of of finding the length of the message queue is
Process.info(pid, :message_queue_len)which avoids copying the whole message queue. Only having:message)_queue_lenin the default info is to NOT copy all the messages unless you explicitly request it.Also Liked
nathanl
I haven’t used this yet, but as of OTP 27.0, you can subscribe to notifications about mailbox lengths.
disableandenableare integer thresholds for when you want receive a message. More explanation is in the docs.rvirding
It is not really the
handle_infocallback which processes the actual message. The GenServer has a top-loop which sits and receives messages arriving at the process. When a message arrives it checks the message format and and calls the relevant callback to handle the message. When the callback returns it goes back into the top-loop and waits for and then processes the next message aand then waits for the next one and then … . In your case it calls thehandle_infocallback with the message.This means that there is no real buffering of messages in the GenServer message queue so checking its length will generally return a small number. The only time the queue can become long is if the GenServer becomes overloaded.
RudManusachi
To find a
pidby process name we could checkProcess.whereis(:name)And now we could see the messages via
Process.info(pid, :messages), but only be careful, as this operation copies all messages to the process that called. So if mailbox is huge - the operation might be expensive.