A FUSE filesystem to collect and store coredumps.
Traditional web applications will "pre-fork" in order to improve parallelism but still support underlying runtimes which do not support multithreading correctly. It's not uncommon to have more than a dozen php or ruby processes, each consuming 400+ MB of memory.
Imagine a situation where all of them crash at the same time. All of the processes will dump core to disk in parallel. The disk will thrash, seeking endlessly between a dozen different huge files being written at once.
An easy solution is to simply disable core dumps, but if you want to be able to fix these bugs, it would be really nice to have a core. Plus if they all crashed at the same time, you probably only need one core anyway.
toiletfs solves this problem by allowing only a single file to be opened at a time. When the kernel tries to open a dozen cores on disk, the first will succeed, and the rest will fail.
toiletfs also supports a executing a shell script after close(), to create a bug report, or alert your monitoring infrastructure.
Why can't you just use core_pattern?
https://bugzilla.redhat.com/show_bug.cgi?id=566460 At some point I'd like to go back and fix this in the kernel, but for production servers, I'd like a solution right now. The kernel fix is complicated enough that it likely won't be eligible for backport into a stable distribution kernel and I'd prefer to avoid maintaining my own binary kernel packages.