@modelcontextprotocol/sdk
Version:
Model Context Protocol implementation for TypeScript
355 lines • 17.5 kB
JavaScript
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.StreamableHTTPClientTransport = exports.StreamableHTTPError = void 0;
const types_js_1 = require("../types.js");
const auth_js_1 = require("./auth.js");
const stream_1 = require("eventsource-parser/stream");
// Default reconnection options for StreamableHTTP connections
const DEFAULT_STREAMABLE_HTTP_RECONNECTION_OPTIONS = {
initialReconnectionDelay: 1000,
maxReconnectionDelay: 30000,
reconnectionDelayGrowFactor: 1.5,
maxRetries: 2,
};
class StreamableHTTPError extends Error {
constructor(code, message) {
super(`Streamable HTTP error: ${message}`);
this.code = code;
}
}
exports.StreamableHTTPError = StreamableHTTPError;
/**
* Client transport for Streamable HTTP: this implements the MCP Streamable HTTP transport specification.
* It will connect to a server using HTTP POST for sending messages and HTTP GET with Server-Sent Events
* for receiving messages.
*/
class StreamableHTTPClientTransport {
constructor(url, opts) {
var _a;
this._url = url;
this._resourceMetadataUrl = undefined;
this._requestInit = opts === null || opts === void 0 ? void 0 : opts.requestInit;
this._authProvider = opts === null || opts === void 0 ? void 0 : opts.authProvider;
this._sessionId = opts === null || opts === void 0 ? void 0 : opts.sessionId;
this._reconnectionOptions = (_a = opts === null || opts === void 0 ? void 0 : opts.reconnectionOptions) !== null && _a !== void 0 ? _a : DEFAULT_STREAMABLE_HTTP_RECONNECTION_OPTIONS;
}
async _authThenStart() {
var _a;
if (!this._authProvider) {
throw new auth_js_1.UnauthorizedError("No auth provider");
}
let result;
try {
result = await (0, auth_js_1.auth)(this._authProvider, { serverUrl: this._url, resourceMetadataUrl: this._resourceMetadataUrl });
}
catch (error) {
(_a = this.onerror) === null || _a === void 0 ? void 0 : _a.call(this, error);
throw error;
}
if (result !== "AUTHORIZED") {
throw new auth_js_1.UnauthorizedError();
}
return await this._startOrAuthSse({ resumptionToken: undefined });
}
async _commonHeaders() {
var _a;
const headers = {};
if (this._authProvider) {
const tokens = await this._authProvider.tokens();
if (tokens) {
headers["Authorization"] = `Bearer ${tokens.access_token}`;
}
}
if (this._sessionId) {
headers["mcp-session-id"] = this._sessionId;
}
return new Headers({ ...headers, ...(_a = this._requestInit) === null || _a === void 0 ? void 0 : _a.headers });
}
async _startOrAuthSse(options) {
var _a, _b;
const { resumptionToken } = options;
try {
// Try to open an initial SSE stream with GET to listen for server messages
// This is optional according to the spec - server may not support it
const headers = await this._commonHeaders();
headers.set("Accept", "text/event-stream");
// Include Last-Event-ID header for resumable streams if provided
if (resumptionToken) {
headers.set("last-event-id", resumptionToken);
}
const response = await fetch(this._url, {
method: "GET",
headers,
signal: (_a = this._abortController) === null || _a === void 0 ? void 0 : _a.signal,
});
if (!response.ok) {
if (response.status === 401 && this._authProvider) {
// Need to authenticate
return await this._authThenStart();
}
// 405 indicates that the server does not offer an SSE stream at GET endpoint
// This is an expected case that should not trigger an error
if (response.status === 405) {
return;
}
throw new StreamableHTTPError(response.status, `Failed to open SSE stream: ${response.statusText}`);
}
this._handleSseStream(response.body, options);
}
catch (error) {
(_b = this.onerror) === null || _b === void 0 ? void 0 : _b.call(this, error);
throw error;
}
}
/**
* Calculates the next reconnection delay using backoff algorithm
*
* @param attempt Current reconnection attempt count for the specific stream
* @returns Time to wait in milliseconds before next reconnection attempt
*/
_getNextReconnectionDelay(attempt) {
// Access default values directly, ensuring they're never undefined
const initialDelay = this._reconnectionOptions.initialReconnectionDelay;
const growFactor = this._reconnectionOptions.reconnectionDelayGrowFactor;
const maxDelay = this._reconnectionOptions.maxReconnectionDelay;
// Cap at maximum delay
return Math.min(initialDelay * Math.pow(growFactor, attempt), maxDelay);
}
/**
* Schedule a reconnection attempt with exponential backoff
*
* @param lastEventId The ID of the last received event for resumability
* @param attemptCount Current reconnection attempt count for this specific stream
*/
_scheduleReconnection(options, attemptCount = 0) {
var _a;
// Use provided options or default options
const maxRetries = this._reconnectionOptions.maxRetries;
// Check if we've exceeded maximum retry attempts
if (maxRetries > 0 && attemptCount >= maxRetries) {
(_a = this.onerror) === null || _a === void 0 ? void 0 : _a.call(this, new Error(`Maximum reconnection attempts (${maxRetries}) exceeded.`));
return;
}
// Calculate next delay based on current attempt count
const delay = this._getNextReconnectionDelay(attemptCount);
// Schedule the reconnection
setTimeout(() => {
// Use the last event ID to resume where we left off
this._startOrAuthSse(options).catch(error => {
var _a;
(_a = this.onerror) === null || _a === void 0 ? void 0 : _a.call(this, new Error(`Failed to reconnect SSE stream: ${error instanceof Error ? error.message : String(error)}`));
// Schedule another attempt if this one failed, incrementing the attempt counter
this._scheduleReconnection(options, attemptCount + 1);
});
}, delay);
}
_handleSseStream(stream, options) {
if (!stream) {
return;
}
const { onresumptiontoken, replayMessageId } = options;
let lastEventId;
const processStream = async () => {
var _a, _b, _c, _d;
// this is the closest we can get to trying to catch network errors
// if something happens reader will throw
try {
// Create a pipeline: binary stream -> text decoder -> SSE parser
const reader = stream
.pipeThrough(new TextDecoderStream())
.pipeThrough(new stream_1.EventSourceParserStream())
.getReader();
while (true) {
const { value: event, done } = await reader.read();
if (done) {
break;
}
// Update last event ID if provided
if (event.id) {
lastEventId = event.id;
onresumptiontoken === null || onresumptiontoken === void 0 ? void 0 : onresumptiontoken(event.id);
}
if (!event.event || event.event === "message") {
try {
const message = types_js_1.JSONRPCMessageSchema.parse(JSON.parse(event.data));
if (replayMessageId !== undefined && (0, types_js_1.isJSONRPCResponse)(message)) {
message.id = replayMessageId;
}
(_a = this.onmessage) === null || _a === void 0 ? void 0 : _a.call(this, message);
}
catch (error) {
(_b = this.onerror) === null || _b === void 0 ? void 0 : _b.call(this, error);
}
}
}
}
catch (error) {
// Handle stream errors - likely a network disconnect
(_c = this.onerror) === null || _c === void 0 ? void 0 : _c.call(this, new Error(`SSE stream disconnected: ${error}`));
// Attempt to reconnect if the stream disconnects unexpectedly and we aren't closing
if (this._abortController && !this._abortController.signal.aborted) {
// Use the exponential backoff reconnection strategy
if (lastEventId !== undefined) {
try {
this._scheduleReconnection({
resumptionToken: lastEventId,
onresumptiontoken,
replayMessageId
}, 0);
}
catch (error) {
(_d = this.onerror) === null || _d === void 0 ? void 0 : _d.call(this, new Error(`Failed to reconnect: ${error instanceof Error ? error.message : String(error)}`));
}
}
}
}
};
processStream();
}
async start() {
if (this._abortController) {
throw new Error("StreamableHTTPClientTransport already started! If using Client class, note that connect() calls start() automatically.");
}
this._abortController = new AbortController();
}
/**
* Call this method after the user has finished authorizing via their user agent and is redirected back to the MCP client application. This will exchange the authorization code for an access token, enabling the next connection attempt to successfully auth.
*/
async finishAuth(authorizationCode) {
if (!this._authProvider) {
throw new auth_js_1.UnauthorizedError("No auth provider");
}
const result = await (0, auth_js_1.auth)(this._authProvider, { serverUrl: this._url, authorizationCode, resourceMetadataUrl: this._resourceMetadataUrl });
if (result !== "AUTHORIZED") {
throw new auth_js_1.UnauthorizedError("Failed to authorize");
}
}
async close() {
var _a, _b;
// Abort any pending requests
(_a = this._abortController) === null || _a === void 0 ? void 0 : _a.abort();
(_b = this.onclose) === null || _b === void 0 ? void 0 : _b.call(this);
}
async send(message, options) {
var _a, _b, _c;
try {
const { resumptionToken, onresumptiontoken } = options || {};
if (resumptionToken) {
// If we have at last event ID, we need to reconnect the SSE stream
this._startOrAuthSse({ resumptionToken, replayMessageId: (0, types_js_1.isJSONRPCRequest)(message) ? message.id : undefined }).catch(err => { var _a; return (_a = this.onerror) === null || _a === void 0 ? void 0 : _a.call(this, err); });
return;
}
const headers = await this._commonHeaders();
headers.set("content-type", "application/json");
headers.set("accept", "application/json, text/event-stream");
const init = {
...this._requestInit,
method: "POST",
headers,
body: JSON.stringify(message),
signal: (_a = this._abortController) === null || _a === void 0 ? void 0 : _a.signal,
};
const response = await fetch(this._url, init);
// Handle session ID received during initialization
const sessionId = response.headers.get("mcp-session-id");
if (sessionId) {
this._sessionId = sessionId;
}
if (!response.ok) {
if (response.status === 401 && this._authProvider) {
this._resourceMetadataUrl = (0, auth_js_1.extractResourceMetadataUrl)(response);
const result = await (0, auth_js_1.auth)(this._authProvider, { serverUrl: this._url, resourceMetadataUrl: this._resourceMetadataUrl });
if (result !== "AUTHORIZED") {
throw new auth_js_1.UnauthorizedError();
}
// Purposely _not_ awaited, so we don't call onerror twice
return this.send(message);
}
const text = await response.text().catch(() => null);
throw new Error(`Error POSTing to endpoint (HTTP ${response.status}): ${text}`);
}
// If the response is 202 Accepted, there's no body to process
if (response.status === 202) {
// if the accepted notification is initialized, we start the SSE stream
// if it's supported by the server
if ((0, types_js_1.isInitializedNotification)(message)) {
// Start without a lastEventId since this is a fresh connection
this._startOrAuthSse({ resumptionToken: undefined }).catch(err => { var _a; return (_a = this.onerror) === null || _a === void 0 ? void 0 : _a.call(this, err); });
}
return;
}
// Get original message(s) for detecting request IDs
const messages = Array.isArray(message) ? message : [message];
const hasRequests = messages.filter(msg => "method" in msg && "id" in msg && msg.id !== undefined).length > 0;
// Check the response type
const contentType = response.headers.get("content-type");
if (hasRequests) {
if (contentType === null || contentType === void 0 ? void 0 : contentType.includes("text/event-stream")) {
// Handle SSE stream responses for requests
// We use the same handler as standalone streams, which now supports
// reconnection with the last event ID
this._handleSseStream(response.body, { onresumptiontoken });
}
else if (contentType === null || contentType === void 0 ? void 0 : contentType.includes("application/json")) {
// For non-streaming servers, we might get direct JSON responses
const data = await response.json();
const responseMessages = Array.isArray(data)
? data.map(msg => types_js_1.JSONRPCMessageSchema.parse(msg))
: [types_js_1.JSONRPCMessageSchema.parse(data)];
for (const msg of responseMessages) {
(_b = this.onmessage) === null || _b === void 0 ? void 0 : _b.call(this, msg);
}
}
else {
throw new StreamableHTTPError(-1, `Unexpected content type: ${contentType}`);
}
}
}
catch (error) {
(_c = this.onerror) === null || _c === void 0 ? void 0 : _c.call(this, error);
throw error;
}
}
get sessionId() {
return this._sessionId;
}
/**
* Terminates the current session by sending a DELETE request to the server.
*
* Clients that no longer need a particular session
* (e.g., because the user is leaving the client application) SHOULD send an
* HTTP DELETE to the MCP endpoint with the Mcp-Session-Id header to explicitly
* terminate the session.
*
* The server MAY respond with HTTP 405 Method Not Allowed, indicating that
* the server does not allow clients to terminate sessions.
*/
async terminateSession() {
var _a, _b;
if (!this._sessionId) {
return; // No session to terminate
}
try {
const headers = await this._commonHeaders();
const init = {
...this._requestInit,
method: "DELETE",
headers,
signal: (_a = this._abortController) === null || _a === void 0 ? void 0 : _a.signal,
};
const response = await fetch(this._url, init);
// We specifically handle 405 as a valid response according to the spec,
// meaning the server does not support explicit session termination
if (!response.ok && response.status !== 405) {
throw new StreamableHTTPError(response.status, `Failed to terminate session: ${response.statusText}`);
}
this._sessionId = undefined;
}
catch (error) {
(_b = this.onerror) === null || _b === void 0 ? void 0 : _b.call(this, error);
throw error;
}
}
}
exports.StreamableHTTPClientTransport = StreamableHTTPClientTransport;
//# sourceMappingURL=streamableHttp.js.map