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Edgar Arakelyanandgensokyo-dev
60bd646478
Add an explicit Streamable HTTP entry for environment/gateway hosts while keeping stdio registrations and default behavior. Preserve the shared provider/session owner across DELETE and replacement; fence and drain tool/completion work before handover or teardown. Bound HTTP input and plain-response admission, cancel refused bodies, join whole exchanges and asynchronous response cleanup before provider hooks, gate startup readiness, and reject queued HTTP/1.1 pipelining while retaining sequential keep-alive. Validation: 8 static/build tasks, 83 adapter tests and registry metadata pass. A real installed gh binary produces seven equivalent CLI/stdio/HTTP reports with DELETE/replacement and clean signal shutdown. Broader local native-provider/ownership failures reproduce on clean main and are documented with limitations in the PR. Co-authored-by: Edgar Arakelyan <edgar.arakelyan@scale.com> Co-authored-by: gensokyo-dev <342580529+gensokyo-dev@users.noreply.github.com>
80 lines
4.6 KiB
Markdown
80 lines
4.6 KiB
Markdown
# Streamable HTTP transport for the MCP server
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Issue: https://github.com/morluto/rea/issues/4933
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## Outcome
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`rea mcp --http [--host H] [--port N]` serves the existing MCP tool catalog over
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the pinned SDK's streamable HTTP transport instead of stdio, so an agent
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environment runtime or any HTTP MCP client can reach REA on a local URL. The
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listener is opt-in: bare `rea mcp`, `rea mcp doctor`, `rea mcp add` and every
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client registration keep stdio.
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## Requirements
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- Route `mcp --http ...` and `--mcp --http ...` to the MCP runtime in the
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dispatcher without changing bare `mcp`, `mcp doctor` or `mcp add`.
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- Resolve host and port from the flags, then `MCP_HOST`/`MCP_PORT` from the
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environment snapshot, then `127.0.0.1` and port `0`; announce the bound URL as
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one pino JSON line on stderr at every log level and leave stdout unused.
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- Use `WebStandardStreamableHTTPServerTransport` in stateful mode around one
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server instance built once, after the listener has bound. `DELETE` ends the session on its transport without
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running the instance's shutdown hooks, so the same instance keeps its
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providers and serves the next client on a fresh transport; the hooks run when
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the listener closes.
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- Let a new client's `initialize` replace a session that is still open, closing
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the earlier transport the same way, so a client that left without `DELETE`
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cannot block the listener; the replaced client's later requests are refused
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(`404` while the replacing session is open).
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- Bridge node:http to web Request/Response in `src/server/http/`, streaming
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response chunks as they are produced and turning a client disconnect into a
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request abort and body cancellation.
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- Classify a loopback bind by the actual bound IP (`127.0.0.0/8`, `::1`, or
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IPv4-mapped loopback), without using the configured DNS name as evidence; validate
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the `Host` and `Origin` headers with the SDK loopback allowlist plus the
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configured name and the bound address on such binds, and relax both for
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other binds and log that relaxation. Refuse scoped IPv6 literals before
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binding, close the listener if its URL cannot be formed, and forward
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listener errors to `onerror` only after a successful bind.
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- Let the caller own instance cleanup (`closeInstance: false`) when its factory
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owner already closes every instance, as the MCP runtime does.
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- Let only an `initialize` that carries the streamable headers and passes those
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checks replace an open session; refuse requests once the slot is closed, join
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an arming session during shutdown, and keep close stages retryable.
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- End the HTTP listener on SIGINT/SIGTERM only, never on stdin EOF, and exit with
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the signal status (`130`/`143`) after cleanup settles; latch a signal that
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arrives during startup so it is acted on as soon as the lifecycle owner exists,
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and exit at once on a second one.
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- Export `serveStreamableHttp({ host, port, createMcpServer, routes, logger })`
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returning `{ url, close }` so an agent environment server can add plain routes
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beside `/mcp` without a second bridge.
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- Keep listener failure causes out of stderr behind a fixed message while the
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typed listen error carries the system cause (such as `EADDRINUSE`) into the
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error-level log line.
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## Acceptance and limits
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Adapters tests cover the bridge (method, URL, headers, body, GET without body,
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incremental streaming, abort and cancel) and the listener (listening line, one
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factory call across three sessions, replacement of an open session by the next
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`initialize`, two `initialize` requests racing to replace one session while the
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instance's shutdown hook stays installed, a working tool call after `DELETE`,
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the instance's shutdown hook firing only when the listener closes, plain
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routes, 404, Host refusal, port release, typed bind failure naming
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`EADDRINUSE`). The dispatcher test covers the new routes and keeps `mcp add
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--http` with the CLI. An mcp-boundary test spawns the built CLI and drives
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initialize, tools/list, `binary_session` and `DELETE` with the SDK streamable
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HTTP client, then proves `binary_session` still answers in the next session and
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in a session that replaced one left open; a process-boundary test asserts
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`143`/`130` exits and a released port. Concurrent clients are not supported:
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the newest `initialize` owns the server. The non-loopback relaxation is covered
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only through its pure allowlist helper; no wide bind runs in tests. Response
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budgets keep their stdio-derived floor; registrations, `rea mcp doctor` and
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`server.json` stay stdio.
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## Deferred issue criteria
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Serving an environment manifest with replayed records, its environment card and
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the exported bundle are later increments of #4933. This PR must reference rather
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than close the issue.
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