Request
The payload of the channel request: the tag byte 4 and the request of the channel.
[4][params JSON …]- The params. The params of the MCP method
resources/list, as JSON. - Malformed. A channel request whose payload does not decode as stated is answered by a channel response finish that no channel response precedes, and the server does nothing else for it.
The channel request is defined by diverge-sdk-rs/src/container_proxy/outside/endpoints/tools/begin/client/channel_request/frame.rs:
//! What a client's channel request frame carries for a tool container
//! begin.
use std::error::Error;
use std::fmt;
use crate::wire::decode::Decode;
use crate::wire::encode::{Encode, Writer};
use crate::shared::containers::postgres;
use crate::shared::containers::daemon;
use crate::shared::containers::secrets::Values;
use crate::shared::mcp;
/// What the server asks the proxy for once a tool container has
/// begun.
///
/// A payload leads with one byte saying which, and the rest is that
/// variant's own bytes.
///
/// | tag | asks for |
/// |-----|----------|
/// | `0` | [`Postgres`](Self::Postgres) |
/// | `1` | [`Info`](Self::Info) |
/// | `2` | [`Daemon`](Self::Daemon) |
/// | `3` | [`McpListTools`](Self::McpListTools) |
/// | `4` | [`McpListResources`](Self::McpListResources) |
/// | `5` | [`McpCallTool`](Self::McpCallTool) |
/// | `6` | [`McpReadResource`](Self::McpReadResource) |
/// | `7` | [`McpNotifications`](Self::McpNotifications) |
/// | `8` | [`Secrets`](Self::Secrets) |
///
/// The first two are the same in both begin scopes, so a reader of
/// one is a reader of both; what follows is this family's own
/// exchange, and then the feed, which both scopes have again under a
/// tag of their own. All of them reach INTO the container: the last
/// hop of what a caller opened on the provider, or of what the caller
/// fed.
#[derive(Debug, Clone, PartialEq)]
pub enum Frame {
/// The server's half of a database connection. Tag `0`.
///
/// Opened once the server has taken the proxy's half, quoting the
/// same connection; what comes back is everything the container's
/// driver wrote. See
/// [`postgres`](crate::shared::containers::postgres) for the pair.
Postgres(postgres::request::Postgres),
/// What the arguments may be. Tag `1`.
///
/// Carries nothing — the variant is bare — and the proxy answers
/// with the image's DIVERGE.md, parsed — read from the
/// container's root, the program never asked — or that it has
/// none. See [`info`](crate::shared::containers::info).
Info,
/// A daemon connection the program opened, by the id the proxy
/// announced: the server's half of it. Tag `2`.
///
/// What comes back on it is everything the PROGRAM sends, as
/// [`daemon::client::Frame`](crate::shared::containers::daemon::client::Frame)s;
/// its finish is the program's socket ended. See
/// [`daemon`](crate::shared::containers::daemon) for the pair.
Daemon(daemon::request::Daemon),
/// What tools the container's server has. Tag `3`.
///
/// The family's own exchange, and the first of five: the caller
/// speaking to the MCP server inside, each of the exchanges in
/// [`shared::mcp`](crate::shared::mcp) on a channel of its own,
/// answered by the container's own server.
McpListTools(mcp::list_tools::request::Request),
/// What resources it has. Tag `4`.
McpListResources(mcp::list_resources::request::Request),
/// Run one of its tools. Tag `5`.
McpCallTool(mcp::call_tool::request::Request),
/// Read one of its resources. Tag `6`.
McpReadResource(mcp::read_resource::request::Request),
/// Everything it says on its own account. Tag `7`.
///
/// Carries nothing, and answers for as long as the channel lives.
McpNotifications(mcp::notifications::request::Request),
/// The secrets' values, fed to the program. Tag `8`.
///
/// Carries the [`Values`] as JSON — every name the program
/// declared, each to its value — which the proxy hands the
/// program on `POST /secrets` and holds until that call answers.
/// Opened by the server once before it sends the run's id and
/// again at every activation, relaying the caller's own feed.
/// Answered once — by a
/// [`feed::response::Frame`](crate::shared::containers::secrets::feed::response::Frame),
/// `Fed` or the program's refusal — and then the finish; a `Fed`
/// opens the gate the proxy holds every exchange behind. See
/// [`secrets`](crate::shared::containers::secrets).
Secrets(Values),
}
/// Tag for [`Frame::Postgres`].
const POSTGRES: u8 = 0;
/// Tag for [`Frame::Info`].
const INFO: u8 = 1;
/// Tag for [`Frame::Daemon`].
const DAEMON: u8 = 2;
/// Tag for [`Frame::McpListTools`].
const MCP_LIST_TOOLS: u8 = 3;
/// Tag for [`Frame::McpListResources`].
const MCP_LIST_RESOURCES: u8 = 4;
/// Tag for [`Frame::McpCallTool`].
const MCP_CALL_TOOL: u8 = 5;
/// Tag for [`Frame::McpReadResource`].
const MCP_READ_RESOURCE: u8 = 6;
/// Tag for [`Frame::McpNotifications`].
const MCP_NOTIFICATIONS: u8 = 7;
/// Tag for [`Frame::Secrets`].
const SECRETS: u8 = 8;
impl Encode for Frame {
/// The ordinary JSON failure, from whichever ask has one.
type Error = serde_json::Error;
fn encode(&self, out: &mut Writer<'_>) -> Result<(), Self::Error> {
match self {
Frame::Postgres(request) => {
out.extend_from_slice(&[POSTGRES]);
// Its error is `Infallible`, and an empty match on one
// is how you say so: there is no value to handle.
request.encode(out).map_err(|error| match error {})
}
Frame::Info => {
out.extend_from_slice(&[INFO]);
Ok(())
}
Frame::Daemon(request) => {
out.extend_from_slice(&[DAEMON]);
request.encode(out).map_err(|error| match error {})
}
Frame::McpListTools(request) => {
out.extend_from_slice(&[MCP_LIST_TOOLS]);
request.encode(out)
}
Frame::McpListResources(request) => {
out.extend_from_slice(&[MCP_LIST_RESOURCES]);
request.encode(out)
}
Frame::McpCallTool(request) => {
out.extend_from_slice(&[MCP_CALL_TOOL]);
request.encode(out)
}
Frame::McpReadResource(request) => {
out.extend_from_slice(&[MCP_READ_RESOURCE]);
request.encode(out)
}
Frame::McpNotifications(request) => {
out.extend_from_slice(&[MCP_NOTIFICATIONS]);
request.encode(out).map_err(|error| match error {})
}
Frame::Secrets(values) => {
out.extend_from_slice(&[SECRETS]);
serde_json::to_writer(out, values)
}
}
}
}
impl Decode<'_> for Frame {
/// Several ways to fail, and the parses among them name which.
type Error = FrameError;
fn decode(bytes: &[u8]) -> Result<Self, Self::Error> {
let (tag, rest) = bytes.split_first().ok_or(FrameError::Empty)?;
match *tag {
POSTGRES => postgres::request::Postgres::decode(rest)
.map(Frame::Postgres)
.map_err(FrameError::Postgres),
INFO => Ok(Frame::Info),
DAEMON => daemon::request::Daemon::decode(rest)
.map(Frame::Daemon)
.map_err(FrameError::Daemon),
MCP_LIST_TOOLS => mcp::list_tools::request::Request::decode(rest)
.map(Frame::McpListTools)
.map_err(FrameError::McpParams),
MCP_LIST_RESOURCES => {
mcp::list_resources::request::Request::decode(rest)
.map(Frame::McpListResources)
.map_err(FrameError::McpParams)
}
MCP_CALL_TOOL => mcp::call_tool::request::Request::decode(rest)
.map(Frame::McpCallTool)
.map_err(FrameError::McpParams),
MCP_READ_RESOURCE => {
mcp::read_resource::request::Request::decode(rest)
.map(Frame::McpReadResource)
.map_err(FrameError::McpParams)
}
MCP_NOTIFICATIONS => Ok(Frame::McpNotifications(
mcp::notifications::request::Request::decode(rest)
.unwrap_or_else(|error| match error {}),
)),
SECRETS => serde_json::from_slice(rest)
.map(Frame::Secrets)
.map_err(FrameError::Secrets),
tag => Err(FrameError::UnknownTag(tag)),
}
}
}
/// A tools begin channel request that could not be read.
#[derive(Debug)]
pub enum FrameError {
/// No bytes at all, so not even a tag.
Empty,
/// A tag that is none of this frame's.
UnknownTag(u8),
/// The connection id was not four bytes.
Postgres(postgres::request::PostgresError),
/// The daemon connection's id was not four bytes.
Daemon(daemon::request::DaemonError),
/// One of the five MCP exchanges' params did not parse.
///
/// One variant for five tags, because they fail the same way and
/// the tag already said which was meant.
McpParams(serde_json::Error),
/// The secrets' values did not parse as JSON. The message is the
/// parser's, which quotes no value.
Secrets(serde_json::Error),
}
impl fmt::Display for FrameError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
FrameError::Empty => {
f.write_str("tools begin channel request frame is empty")
}
FrameError::UnknownTag(tag) => {
write!(f, "unknown tools begin channel request tag {tag}")
}
FrameError::Postgres(error) => write!(f, "{error}"),
FrameError::Daemon(error) => write!(f, "{error}"),
FrameError::McpParams(error) => {
write!(f, "mcp request params did not parse: {error}")
}
FrameError::Secrets(error) => {
write!(f, "secrets feed did not parse: {error}")
}
}
}
}
impl Error for FrameError {
fn source(&self) -> Option<&(dyn Error + 'static)> {
match self {
FrameError::McpParams(error) | FrameError::Secrets(error) => Some(error),
FrameError::Postgres(error) => Some(error),
FrameError::Daemon(error) => Some(error),
FrameError::Empty | FrameError::UnknownTag(_) => None,
}
}
}and by diverge-sdk-rs/src/shared/mcp/list_resources/request/request.rs:
//! Asking what resources there are.
use rmcp::model::{PaginatedRequestParams};
use serde_json::Error;
use crate::wire::decode::Decode;
use crate::wire::encode::{Encode, Writer};
/// Where in the listing to start, if anywhere in particular.
///
/// The same shape [`list_tools`](crate::shared::mcp::list_tools) has, for
/// the same reason: it is the same MCP request against a different
/// noun.
///
/// # It is a wrapper, and a thin one
///
/// [`rmcp`] already defines the shape and this crate has no business
/// redefining it — an MCP request has one form and it is MCP's. What
/// the wrapper adds is the two impls beneath it, so that a channel
/// request carrying one writes `request.encode(out)` like every other
/// payload in this crate rather than reaching for `serde_json` itself.
#[derive(Debug, Clone, PartialEq, Default)]
pub struct Request(
/// The parameters, as [`rmcp`] defines them.
pub Option<PaginatedRequestParams>,
);
/// Its JSON, and nothing in front of it. The tag that says which
/// request this is belongs to whichever frame carries it.
impl Encode for Request {
/// The ordinary JSON failure.
type Error = Error;
fn encode(&self, out: &mut Writer<'_>) -> Result<(), Error> {
serde_json::to_writer(out, &self.0)
}
}
impl Decode<'_> for Request {
/// The ordinary JSON failure. There is nothing else here to get
/// wrong — no tag to be unknown, and no empty case, since no bytes
/// at all is a JSON document that ended too early and is reported
/// as one.
type Error = Error;
fn decode(bytes: &[u8]) -> Result<Self, Error> {
serde_json::from_slice(bytes).map(Request)
}
}