Cross-Platform Process Containment: Job Objects vs Process Groups vs cgroups

Sat, 26 Sep 2026 16:20:00 -0700

Every turn a shipmates crew member takes is a subprocess. It’s claude or the codex app-server. That in turn spawns shells, go test, npm or whatever the task calls for. Two things have to be true about that tree. When a turn ends or gets killed, the whole tree goes, including the grandchildren. And if somebody sets a memory or CPU budget, the budget applies to the whole tree, not just the process I happened to start.

Per-Tenant Network Policy in One Process: ePHPm's eBPF Thread Tags

Fri, 28 Aug 2026 20:40:00 -0700

In multi-tenant mode ePHPm serves every site in sites_dir from one process. Every tenant’s PHP runs as the same OS user on the same pool of ZTS threads. A thread that just served blog.example will serve shop.example a few milliseconds later. That’s the density win. It also means the kernel has no idea which tenant is behind a given connect(). As far as Linux is concerned it’s all ephpm-web.

Most of the isolation work in ePHPm happens above the kernel. That covers open_basedir, the function denylist, per-site databases and KV keyspaces. Network is the one place where that isn’t enough. This week we brought eBPF in to give the kernel a per-tenant identity. It went from a roadmap doc on Wednesday morning to merged that evening (#413, aimed at v0.8.1). v0.8.1 never got a release because its Linux legs failed to link. v0.8.2 shipped with the BPF object silently stubbed out. v0.8.3 was the first release that carried it. This post covers what it enforces and what it costs. It also covers what broke on the way out the door and what it doesn’t do.

Cgroups on Luther Monson

Cross-Platform Process Containment: Job Objects vs Process Groups vs cgroups

Per-Tenant Network Policy in One Process: ePHPm's eBPF Thread Tags