worker-shell

worker-shell example

Important

PREVIEW ONLY This package is provided as a preview for feedback only. APIs are unstable and the design is subject to change.

A Cloudflare Worker + Durable Object that runs a Workspace whose shell is a Dynamic Worker loaded through env.LOADER. The shell is just-bash; the user-facing HTTP surface mirrors examples/container so the same curl recipes work, just without the container.

Architecture

client ─► Worker /c/<name>/{file,exec}
             │  (DO RPC calls)
             ▼
       DO (ContainerExample) ──► Workspace ──► WorkerShellBackend
                                                    │
                                                    │  env.LOADER.get(...)
                                                    ▼
                                              Dynamic Worker
                                              (ShellWorker)
                                                    │
                                                    │  env.HOST.get(id)
                                                    │    .getWorkspace()
                                                    ▼
                                          back to ContainerExample DO

1. The DO constructs a WorkerShellBackend from @cloudflare/computer/backends/worker-shell, passing the Loader binding, a {binding, id} reference to itself, and ctx. The backend handles the rest internally: it builds the Loader callback (with the code-split shell modules + the seek-bzip stub), mints a WorkspaceServiceProxy loopback through ctx.exports.WorkspaceServiceProxy(...), calls env.LOADER.get(...).getEntrypoint("ShellWorker"), and turns the resulting Fetcher into a ShellRPC.
2. The loader callback wires the WorkspaceServiceProxy loopback into the Dynamic Worker's env.HOST. The proxy is a small WorkerEntrypoint whose getWorkspace() method does the namespace lookup on the host side and returns a WorkspaceStub. A raw DurableObjectNamespace doesn't survive structured clone into the loader's env; the binding-shape Fetcher the proxy produces does.
3. ShellWorker (shipped in @cloudflare/computer/backends/worker-shell) lives inside that Dynamic Worker. Each exec(input) calls env.HOST.getWorkspace(), builds a fresh Bash around a WorkspaceFsAdapter wrapping the stub's .fs, runs the command, and disposes the stub when the run settles.
4. Filesystem operations from inside Bash round-trip through the host DO's own RPC surface, so storage handles stay valid and one workspace per DO is the natural boundary.
5. BackendHandle.sync is "none". There's a single authoritative store (the DO's SQLite); push and pull short-circuit. ExecResult.pushed / pulled are always zero.

The DO is a thin host. There's no Dockerfile; the Dynamic Worker lifecycle is the loader's problem.

Paths

PUT /c/<name>/file/workspace/hello.txt writes /workspace/hello.txt, and GET /c/<name>/file/workspace/r2/x reads /workspace/r2/x — the URL and the on-disk path always match. Any URL outside /workspace returns 400.

exec runs with cwd defaulting to /workspace. Commands run inside the just-bash interpreter — broad textual tooling (cat, grep, awk, sed, jq, sort, …) but not the full Linux userland. The Dynamic Worker has globalOutbound: null, so the shell can't reach the public internet on its own.

R2 mount

Identical to the container example. Seed once with:

npm run seed:r2:local --workspace @example/computer-worker-shell

# or after deploy
npm run seed:r2 --workspace @example/computer-worker-shell

HTTP surface

PUT  /c/<name>/file/workspace/<path>   raw body → writeFile at /workspace/<path>
GET  /c/<name>/file/workspace/<path>   octet-stream of /workspace/<path>
                                       (any path outside /workspace returns 400)
POST /c/<name>/exec                    { command | argv, cwd?, encoding? }
                                       cwd defaults to /workspace
                                       → JSON { exitCode, stdout, stderr }

Run it locally

No Docker, no extra build step. The shell ships as a record of pre-bundled modules (SHELL_MODULES) inside @cloudflare/computer/backends/worker-shell; WorkerShellBackend spreads the whole record into the Loader callback internally so the DO constructor stays a three-line backend invocation. The entry module parses on cold start; the dynamic chunks (python, js-exec, sqlite, curl, html-to-markdown) stay cold until a script reaches for them.

npm run dev --workspace @example/computer-worker-shell

Smoke test (same recipes as the container example):

curl http://127.0.0.1:8787/

echo 'hello' | curl -X PUT --data-binary @- \
  http://127.0.0.1:8787/c/demo/file/workspace/hello.txt

curl http://127.0.0.1:8787/c/demo/file/workspace/hello.txt

curl -X POST http://127.0.0.1:8787/c/demo/exec \
  -H 'content-type: application/json' \
  -d '{"command":"cat hello.txt && wc -l hello.txt","encoding":"utf8"}'

Layout

examples/worker-shell/
  wrangler.jsonc    Worker + DO + worker_loaders binding
  src/index.ts      Worker handler + DO (ContainerExample)

Nothing else. The Dynamic Worker source ships from @cloudflare/computer/backends/worker-shell as a pre-built module string.

Known limitations

• Exec is run-and-collect. The handler awaits handle.result() and emits one JSON response. just-bash itself doesn't stream chunks; the shell emits at most one stdout event and one stderr event per run.
• getExec reattach is intentionally absent. Each exec is scoped to its own call; an id observed in one envelope can't be reached from a later request.
• PATH-walk diagnostics in wrangler dev. just-bash probes every $PATH directory for every command name. Each miss prints an Uncaught WorkspaceFsError: no such path: ... in the dev log, even though just-bash catches the rejection locally. Cosmetic; exec returns the correct result.