Limitations

Playground

The playground (v0.7.0, built on engine v0.30.1) takes one wctr command per line, with no pipes in that line. It has exec, a shell (the shell image), typing into exec -i, and run -it and start -ai (its end-to-end test runs wctr run --rm -it shell). Its dashboard is v0.8.0, so GPU panes send input there (click a pane to focus it; vertex buffers and depth-stencil are not served). -p works in the browser since v0.5.0, in a tab of its own, for HTTP and (v0.6.0) WebDAV methods; there is no UDP and no raw TCP from outside the page. Networks stay inside the page: no Internet. Ctrl-C stops waiting for a container but leaves it running. Each container is bounded: 256 MiB of memory, a 5-minute run, 64 MiB of writes, 4 MiB of logs, and 64 containers at once.

The default UI, the dashboard, makes the page slower to be ready than the terminal page (728 ms against 1070 ms in Chromium on the live site), because dashboard.wasm was 20.45 MB raw (5.32 MB gzipped) when measured; dashboard v0.4.2 made it smaller and no newer figure has been measured. The terminal-only page is at ?ui=terminal.

Engine

Engine v0.31.0 does not have:

• CPU accounting: a WebAssembly guest gives none, so wctr stats shows CPU as --;
• host-path volumes: only named volumes exist, and a host path is refused;
• signals: processes are the WASIX subset, a child is stopped only with its container, and Ctrl-C in a terminal erases the line (a container’s first process has its own stdin and terminal since v0.30.0: run -it, attach);
• published ports with sockets in the browser (-p works natively since v0.22.0, and in the playground since v0.5.0 with no socket, through portmap.Virtual (v0.24.0) and a second origin; natively there is no SCTP, and the source address the guest sees is its own). A container on several networks binds to its primary address or to all (0.0.0.0), not to a secondary address alone; aliases work on in-engine networks only; no IPv6 on in-engine networks; the DNS shadows a container’s own UDP server on port 53 at the resolver addresses (see Networking);
• a Kubernetes API, and volume drivers or tmpfs;
• a distinct quota error: when a container exhausts its storage quota, the write surfaces to the module as EIO.

wctr build runs shell-form RUN from engine v0.17.0 on the shell base image (shell v0.1.0, ghcr.io/go-wasmcontainers/shell:0.1.0, public). See Build and Shell.