feat: implement MCP streamable HTTP server

2026-03-25 20:02:23 +03:00
parent a776ae4a73
commit 752288ca70
11 changed files with 1031 additions and 156 deletions
@@ -0,0 +1,558 @@
+use std::{sync::Arc, time::Duration};
+
+use axum::{
+    Json, Router,
+    extract::State,
+    http::{
+        HeaderMap, HeaderValue, StatusCode,
+        header::{self, ACCEPT},
+    },
+    response::{IntoResponse, Response},
+    routing::get,
+};
+use mcpaas_registry::{PostgresRegistry, RegistryOperation};
+use mcpaas_runtime::{RuntimeError, RuntimeExecutor, RuntimeOperation};
+use serde::{Deserialize, Serialize};
+use serde_json::{Value, json};
+
+use crate::{
+    catalog::PublishedToolCatalog,
+    jsonrpc::{
+        CURRENT_PROTOCOL_VERSION, DEFAULT_PROTOCOL_VERSION, is_notification, is_request,
+        is_response, jsonrpc_error, jsonrpc_result, method_name, negotiated_protocol_version,
+        params, request_id,
+    },
+    session::{SessionState, SessionStore},
+};
+
+const HEADER_MCP_SESSION_ID: &str = "MCP-Session-Id";
+const HEADER_MCP_PROTOCOL_VERSION: &str = "MCP-Protocol-Version";
+
+#[derive(Clone)]
+pub struct AppState {
+    catalog: PublishedToolCatalog,
+    runtime: RuntimeExecutor,
+    sessions: SessionStore,
+    allowed_origins: AllowedOrigins,
+}
+
+#[derive(Clone)]
+pub struct AllowedOrigins {
+    public_origin: Option<String>,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+struct InitializeParams {
+    #[serde(rename = "protocolVersion")]
+    protocol_version: String,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+struct ToolCallParams {
+    name: String,
+    #[serde(default)]
+    arguments: Value,
+}
+
+pub fn build_app(
+    registry: PostgresRegistry,
+    refresh_interval: Duration,
+    public_base_url: Option<String>,
+) -> Router {
+    let state = Arc::new(AppState {
+        catalog: PublishedToolCatalog::new(registry, refresh_interval),
+        runtime: RuntimeExecutor::new(),
+        sessions: SessionStore::new(),
+        allowed_origins: AllowedOrigins::new(public_base_url),
+    });
+
+    Router::new()
+        .route("/health", get(health))
+        .route("/", get(mcp_get).post(mcp_post).delete(mcp_delete))
+        .route("/mcp", get(mcp_get).post(mcp_post).delete(mcp_delete))
+        .with_state(state)
+}
+
+async fn health() -> Json<Value> {
+    Json(json!({
+        "service": "mcp-server",
+        "status": "ok"
+    }))
+}
+
+async fn mcp_get() -> Response {
+    StatusCode::METHOD_NOT_ALLOWED.into_response()
+}
+
+async fn mcp_delete(State(state): State<Arc<AppState>>, headers: HeaderMap) -> Response {
+    match session_id_from_headers(&headers) {
+        Ok(Some(session_id)) => {
+            if state.sessions.delete(&session_id).await {
+                StatusCode::NO_CONTENT.into_response()
+            } else {
+                StatusCode::NOT_FOUND.into_response()
+            }
+        }
+        Ok(None) => StatusCode::BAD_REQUEST.into_response(),
+        Err(status) => status.into_response(),
+    }
+}
+
+async fn mcp_post(
+    State(state): State<Arc<AppState>>,
+    headers: HeaderMap,
+    Json(message): Json<Value>,
+) -> Response {
+    if let Err(status) = validate_origin(&state.allowed_origins, &headers) {
+        return status.into_response();
+    }
+
+    if let Err(status) = validate_accept_header(&headers) {
+        return status.into_response();
+    }
+
+    if is_response(&message) || is_notification(&message) && method_name(&message).is_none() {
+        return StatusCode::ACCEPTED.into_response();
+    }
+
+    let protocol_version = match protocol_version_from_headers(&headers) {
+        Ok(value) => value,
+        Err(status) => return status.into_response(),
+    };
+
+    match method_name(&message) {
+        Some("initialize") if is_request(&message) => handle_initialize(state, &message).await,
+        Some("notifications/initialized") if is_notification(&message) => {
+            handle_initialized_notification(state, &headers).await
+        }
+        Some("ping") if is_request(&message) => {
+            let session = match require_initialized_session(&state, &headers, &message).await {
+                Ok(session) => session,
+                Err(response) => return response,
+            };
+
+            json_response(
+                StatusCode::OK,
+                jsonrpc_result(
+                    request_id(&message),
+                    json!({ "protocolVersion": session.protocol_version }),
+                ),
+                None,
+                Some(&protocol_version),
+            )
+        }
+        Some("tools/list") if is_request(&message) => {
+            let session = match require_initialized_session(&state, &headers, &message).await {
+                Ok(session) => session,
+                Err(response) => return response,
+            };
+
+            match state.catalog.list_tools().await {
+                Ok(tools) => {
+                    let definitions = tools.iter().map(tool_definition).collect::<Vec<_>>();
+
+                    json_response(
+                        StatusCode::OK,
+                        jsonrpc_result(request_id(&message), json!({ "tools": definitions })),
+                        None,
+                        Some(&session.protocol_version),
+                    )
+                }
+                Err(error) => internal_jsonrpc_error(&message, error),
+            }
+        }
+        Some("tools/call") if is_request(&message) => {
+            let session = match require_initialized_session(&state, &headers, &message).await {
+                Ok(session) => session,
+                Err(response) => return response,
+            };
+            let tool_call_params: ToolCallParams = match serde_json::from_value(params(&message)) {
+                Ok(value) => value,
+                Err(error) => {
+                    return json_response(
+                        StatusCode::OK,
+                        jsonrpc_error(request_id(&message), -32602, error.to_string()),
+                        None,
+                        Some(&session.protocol_version),
+                    );
+                }
+            };
+
+            let arguments = if tool_call_params.arguments.is_null() {
+                json!({})
+            } else {
+                tool_call_params.arguments
+            };
+
+            match state.catalog.get_tool(&tool_call_params.name).await {
+                Ok(Some(operation)) => {
+                    match state
+                        .runtime
+                        .execute(&RuntimeOperation::from(operation), &arguments)
+                        .await
+                    {
+                        Ok(output) => json_response(
+                            StatusCode::OK,
+                            jsonrpc_result(
+                                request_id(&message),
+                                json!({
+                                    "content": [
+                                        {
+                                            "type": "text",
+                                            "text": serde_json::to_string_pretty(&output).unwrap_or_else(|_| "{}".to_owned())
+                                        }
+                                    ],
+                                    "structuredContent": output,
+                                    "isError": false
+                                }),
+                            ),
+                            None,
+                            Some(&session.protocol_version),
+                        ),
+                        Err(error) => json_response(
+                            StatusCode::OK,
+                            jsonrpc_result(
+                                request_id(&message),
+                                json!({
+                                    "content": [
+                                        {
+                                            "type": "text",
+                                            "text": error.to_string()
+                                        }
+                                    ],
+                                    "structuredContent": {
+                                        "error": {
+                                            "code": runtime_error_code(&error),
+                                            "message": error.to_string()
+                                        }
+                                    },
+                                    "isError": true
+                                }),
+                            ),
+                            None,
+                            Some(&session.protocol_version),
+                        ),
+                    }
+                }
+                Ok(None) => json_response(
+                    StatusCode::OK,
+                    jsonrpc_error(
+                        request_id(&message),
+                        -32602,
+                        format!("tool {} was not found", tool_call_params.name),
+                    ),
+                    None,
+                    Some(&session.protocol_version),
+                ),
+                Err(error) => internal_jsonrpc_error(&message, error),
+            }
+        }
+        Some(method) if is_notification(&message) => {
+            let _ = method;
+            StatusCode::ACCEPTED.into_response()
+        }
+        Some(method) => json_response(
+            StatusCode::OK,
+            jsonrpc_error(
+                request_id(&message),
+                -32601,
+                format!("method {method} is not supported"),
+            ),
+            None,
+            Some(&protocol_version),
+        ),
+        None => json_response(
+            StatusCode::BAD_REQUEST,
+            jsonrpc_error(Value::Null, -32600, "invalid JSON-RPC message"),
+            None,
+            Some(&protocol_version),
+        ),
+    }
+}
+
+async fn handle_initialize(state: Arc<AppState>, message: &Value) -> Response {
+    let initialize_params: InitializeParams = match serde_json::from_value(params(message)) {
+        Ok(value) => value,
+        Err(error) => {
+            return json_response(
+                StatusCode::OK,
+                jsonrpc_error(request_id(message), -32602, error.to_string()),
+                None,
+                Some(DEFAULT_PROTOCOL_VERSION),
+            );
+        }
+    };
+    let Some(protocol_version) = negotiated_protocol_version(&initialize_params.protocol_version)
+    else {
+        return json_response(
+            StatusCode::OK,
+            jsonrpc_error(
+                request_id(message),
+                -32602,
+                format!(
+                    "unsupported protocol version {}",
+                    initialize_params.protocol_version
+                ),
+            ),
+            None,
+            Some(DEFAULT_PROTOCOL_VERSION),
+        );
+    };
+    let session_id = state.sessions.create(protocol_version).await;
+
+    json_response(
+        StatusCode::OK,
+        jsonrpc_result(
+            request_id(message),
+            json!({
+                "protocolVersion": protocol_version,
+                "capabilities": {
+                    "tools": {
+                        "listChanged": false
+                    }
+                },
+                "serverInfo": {
+                    "name": "rmcp-mcp-server",
+                    "version": env!("CARGO_PKG_VERSION")
+                }
+            }),
+        ),
+        Some(&session_id),
+        Some(protocol_version),
+    )
+}
+
+async fn handle_initialized_notification(state: Arc<AppState>, headers: &HeaderMap) -> Response {
+    match session_id_from_headers(headers) {
+        Ok(Some(session_id)) => {
+            if state.sessions.mark_initialized(&session_id).await {
+                StatusCode::ACCEPTED.into_response()
+            } else {
+                StatusCode::NOT_FOUND.into_response()
+            }
+        }
+        Ok(None) => StatusCode::BAD_REQUEST.into_response(),
+        Err(status) => status.into_response(),
+    }
+}
+
+async fn require_initialized_session(
+    state: &Arc<AppState>,
+    headers: &HeaderMap,
+    message: &Value,
+) -> Result<SessionState, Response> {
+    let session_id = match session_id_from_headers(headers) {
+        Ok(Some(session_id)) => session_id,
+        Ok(None) => return Err(StatusCode::BAD_REQUEST.into_response()),
+        Err(status) => return Err(status.into_response()),
+    };
+
+    let Some(session) = state.sessions.get(&session_id).await else {
+        return Err(StatusCode::NOT_FOUND.into_response());
+    };
+
+    if !session.initialized {
+        return Err(json_response(
+            StatusCode::OK,
+            jsonrpc_error(request_id(message), -32002, "session is not initialized"),
+            None,
+            Some(&session.protocol_version),
+        ));
+    }
+
+    Ok(session)
+}
+
+fn validate_origin(
+    allowed_origins: &AllowedOrigins,
+    headers: &HeaderMap,
+) -> Result<(), StatusCode> {
+    let Some(origin) = headers.get(header::ORIGIN) else {
+        return Ok(());
+    };
+    let Ok(origin) = origin.to_str() else {
+        return Err(StatusCode::FORBIDDEN);
+    };
+
+    if allowed_origins.is_allowed(origin) {
+        return Ok(());
+    }
+
+    Err(StatusCode::FORBIDDEN)
+}
+
+fn validate_accept_header(headers: &HeaderMap) -> Result<(), StatusCode> {
+    let Some(accept) = headers.get(ACCEPT) else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+    let Ok(accept) = accept.to_str() else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+    let normalized = accept.to_ascii_lowercase();
+
+    if normalized.contains("application/json") && normalized.contains("text/event-stream") {
+        return Ok(());
+    }
+
+    Err(StatusCode::NOT_ACCEPTABLE)
+}
+
+fn protocol_version_from_headers(headers: &HeaderMap) -> Result<String, StatusCode> {
+    let Some(version) = headers.get(HEADER_MCP_PROTOCOL_VERSION) else {
+        return Ok(DEFAULT_PROTOCOL_VERSION.to_owned());
+    };
+    let Ok(version) = version.to_str() else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+
+    if negotiated_protocol_version(version).is_some() {
+        return Ok(version.to_owned());
+    }
+
+    Err(StatusCode::BAD_REQUEST)
+}
+
+fn session_id_from_headers(headers: &HeaderMap) -> Result<Option<String>, StatusCode> {
+    let Some(session_id) = headers.get(HEADER_MCP_SESSION_ID) else {
+        return Ok(None);
+    };
+    let Ok(session_id) = session_id.to_str() else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+
+    Ok(Some(session_id.to_owned()))
+}
+
+fn internal_jsonrpc_error(message: &Value, error: impl std::fmt::Display) -> Response {
+    json_response(
+        StatusCode::INTERNAL_SERVER_ERROR,
+        jsonrpc_error(request_id(message), -32603, error.to_string()),
+        None,
+        Some(DEFAULT_PROTOCOL_VERSION),
+    )
+}
+
+fn runtime_error_code(error: &RuntimeError) -> &'static str {
+    match error {
+        RuntimeError::Schema(_) => "schema_validation_error",
+        RuntimeError::Mapping(_) => "mapping_error",
+        RuntimeError::RestAdapter(_) => "adapter_execution_error",
+        RuntimeError::UnsupportedProtocol { .. } => "unsupported_protocol",
+        RuntimeError::InvalidPreparedRequest { .. } => "runtime_error",
+    }
+}
+
+fn json_response(
+    status: StatusCode,
+    payload: Value,
+    session_id: Option<&str>,
+    protocol_version: Option<&str>,
+) -> Response {
+    let mut response = (status, Json(payload)).into_response();
+
+    if let Some(session_id) = session_id {
+        response.headers_mut().insert(
+            HEADER_MCP_SESSION_ID,
+            HeaderValue::from_str(session_id)
+                .unwrap_or_else(|_| HeaderValue::from_static("invalid")),
+        );
+    }
+
+    if let Some(protocol_version) = protocol_version {
+        response.headers_mut().insert(
+            HEADER_MCP_PROTOCOL_VERSION,
+            HeaderValue::from_str(protocol_version)
+                .unwrap_or_else(|_| HeaderValue::from_static(CURRENT_PROTOCOL_VERSION)),
+        );
+    }
+
+    response
+}
+
+fn tool_definition(operation: &RegistryOperation) -> Value {
+    json!({
+        "name": operation.name,
+        "title": operation.tool_description.title,
+        "description": operation.tool_description.description,
+        "inputSchema": schema_to_json_schema(&operation.input_schema)
+    })
+}
+
+fn schema_to_json_schema(schema: &mcpaas_schema::Schema) -> Value {
+    match schema.kind {
+        mcpaas_schema::SchemaKind::Object => {
+            let mut properties = serde_json::Map::new();
+            let mut required = Vec::new();
+
+            for (field_name, field_schema) in &schema.fields {
+                properties.insert(field_name.clone(), schema_to_json_schema(field_schema));
+
+                if field_schema.required {
+                    required.push(Value::String(field_name.clone()));
+                }
+            }
+
+            json!({
+                "type": "object",
+                "properties": properties,
+                "required": required
+            })
+        }
+        mcpaas_schema::SchemaKind::Array => json!({
+            "type": "array",
+            "items": schema
+                .items
+                .as_deref()
+                .map(schema_to_json_schema)
+                .unwrap_or_else(|| json!({}))
+        }),
+        mcpaas_schema::SchemaKind::String => json!({ "type": "string" }),
+        mcpaas_schema::SchemaKind::Integer => json!({ "type": "integer" }),
+        mcpaas_schema::SchemaKind::Number => json!({ "type": "number" }),
+        mcpaas_schema::SchemaKind::Boolean => json!({ "type": "boolean" }),
+        mcpaas_schema::SchemaKind::Enum => json!({
+            "type": "string",
+            "enum": schema.enum_values
+        }),
+        mcpaas_schema::SchemaKind::Null => json!({ "type": "null" }),
+        mcpaas_schema::SchemaKind::Oneof => json!({
+            "anyOf": schema.variants.iter().map(schema_to_json_schema).collect::<Vec<_>>()
+        }),
+    }
+}
+
+impl AllowedOrigins {
+    fn new(public_base_url: Option<String>) -> Self {
+        Self {
+            public_origin: public_base_url.and_then(|value| extract_origin(&value)),
+        }
+    }
+
+    fn is_allowed(&self, origin: &str) -> bool {
+        if origin.starts_with("http://localhost")
+            || origin.starts_with("http://127.0.0.1")
+            || origin.starts_with("https://localhost")
+            || origin.starts_with("https://127.0.0.1")
+        {
+            return true;
+        }
+
+        match &self.public_origin {
+            Some(public_origin) => public_origin == origin,
+            None => false,
+        }
+    }
+}
+
+fn extract_origin(url: &str) -> Option<String> {
+    let mut parts = url.split('/');
+    let scheme = parts.next()?;
+    let empty = parts.next()?;
+    let authority = parts.next()?;
+
+    if empty.is_empty() {
+        return Some(format!("{scheme}//{authority}"));
+    }
+
+    None
+}