Yep; as I mentioned elsewhere, I'm not discounting mailboxes filling faster than you can handle them, but rather the idea that you have 'problematic mails in the mailbox' - I've never had problematic mail in the mailbox. I've certainly seen mailboxes grow, because they were receiving messages faster than I was processing them, and i had to rethink my design. But that isn't an issue with the mail going into the mailbox; that's an issue with my not scaling out my receivers to fit the load. As I mentioned elsewhere, that may seem like semantics, but to me it isn't; it means the language's working that way makes sense, and it's rather an issue that I created a bottleneck with no way to relieve the pressure (as compared to messages that can't be handled and just sit there causing receives to take longer and longer over time).
Oh, I think I see. I don't think there's such thing as a problematic mail for BEAM really, mails are just terms, and BEAM handles terms, no problem. A mail that contained a small slice of a very large binary, would of course keep the whole referenced binary hanging around, which could be bad, or a large tuple could be bad because if you tried to inspect the message queue through process_info in another process, that would be a big copy.
But I think maybe the original poster just meant lots of bad mail in the mailbox to mean mail that would take a long time to process, because of how the receiving process will handle it.
Or, possibly bad mail meaning (as you suggest, perhaps), mail that won't be matched by any receive, resulting in longer and longer receives when they need to start from the top.
"But I think maybe the original poster just meant lots of bad mail in the mailbox to mean mail that would take a long time to process, because of how the receiving process will handle it."
Yeah; just, if he meant that, it seems like a...weird call out. Since that's not particular to Erlang's messaging model; that's true in any system where you have a synchronization point that is being hit faster than it can execute. Seems weird to call that out as a notable problem, as such.
What's unique to Erlang, and -could- be prevented (by limiting a process to a single receive block, and having a type system prevent sending any messages not in that receive block), if you wanted to change the model, is the fact I can send arbitrary messages to a process, that will never match on them, and because it's a queue, will cause it to delay all following messages from being handled. Hence my focusing on that; yes, that's a potential problem, no, it's not a particularly likely one.
