Class: MCPClient::ServerStreamableHTTP

Inherits:
ServerBase
  • Object
show all
Includes:
JsonRpcTransport
Defined in:
lib/mcp_client/server_streamable_http.rb,
lib/mcp_client/server_streamable_http/json_rpc_transport.rb

Overview

Implementation of MCP server that communicates via Streamable HTTP transport This transport uses HTTP POST requests but expects Server-Sent Event formatted responses It’s designed for servers that support streaming responses over HTTP

Defined Under Namespace

Modules: JsonRpcTransport

Constant Summary collapse

DEFAULT_READ_TIMEOUT =

Default values for connection settings

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DEFAULT_MAX_RETRIES = 
3

Instance Attribute Summary collapse

Attributes inherited from ServerBase

#name

Instance Method Summary collapse

Methods included from HttpTransportBase

#rpc_notify, #rpc_request, #valid_server_url?, #valid_session_id?

Methods included from JsonRpcCommon

#build_jsonrpc_notification, #build_jsonrpc_request, #initialization_params, #ping, #process_jsonrpc_response, #with_retry

Methods inherited from ServerBase

#on_notification, #ping, #rpc_notify, #rpc_request

Constructor Details

#initialize(base_url:, **options) ⇒ ServerStreamableHTTP

Returns a new instance of ServerStreamableHTTP.

Parameters:

  • The base URL of the MCP server

  • Server configuration options (same as ServerHTTP)

Raises:



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# File 'lib/mcp_client/server_streamable_http.rb', line 41

def initialize(base_url:, **options)
  opts = default_options.merge(options)
  super(name: opts[:name])
  @logger = opts[:logger] || Logger.new($stdout, level: Logger::WARN)
  @logger.progname = self.class.name
  @logger.formatter = proc { |severity, _datetime, progname, msg| "#{severity} [#{progname}] #{msg}\n" }

  @max_retries = opts[:retries]
  @retry_backoff = opts[:retry_backoff]

  # Validate and normalize base_url
  raise ArgumentError, "Invalid or insecure server URL: #{base_url}" unless valid_server_url?(base_url)

  # Normalize base_url and handle cases where full endpoint is provided in base_url
  uri = URI.parse(base_url.chomp('/'))

  # Helper to build base URL without default ports
  build_base_url = lambda do |parsed_uri|
    port_part = if parsed_uri.port &&
                   !((parsed_uri.scheme == 'http' && parsed_uri.port == 80) ||
                     (parsed_uri.scheme == 'https' && parsed_uri.port == 443))
                  ":#{parsed_uri.port}"
                else
                  ''
                end
    "#{parsed_uri.scheme}://#{parsed_uri.host}#{port_part}"
  end

  @base_url = build_base_url.call(uri)
  @endpoint = if uri.path && !uri.path.empty? && uri.path != '/' && opts[:endpoint] == '/rpc'
                # If base_url contains a path and we're using default endpoint,
                # treat the path as the endpoint and use the base URL without path
                uri.path
              else
                # Standard case: base_url is just scheme://host:port, endpoint is separate
                opts[:endpoint]
              end

  # Set up headers for Streamable HTTP requests
  @headers = opts[:headers].merge({
                                    'Content-Type' => 'application/json',
                                    'Accept' => 'text/event-stream, application/json',
                                    'Accept-Encoding' => 'gzip, deflate',
                                    'User-Agent' => "ruby-mcp-client/#{MCPClient::VERSION}",
                                    'Cache-Control' => 'no-cache'
                                  })

  @read_timeout = opts[:read_timeout]
  @tools = nil
  @tools_data = nil
  @request_id = 0
  @mutex = Monitor.new
  @connection_established = false
  @initialized = false
  @http_conn = nil
  @session_id = nil
  @last_event_id = nil
  @oauth_provider = opts[:oauth_provider]
end

Instance Attribute Details

#base_url ⇒ String (readonly)

Returns The base URL of the MCP server.

Returns:

  • The base URL of the MCP server



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# File 'lib/mcp_client/server_streamable_http.rb', line 29

def base_url
  @base_url
end

#capabilities ⇒ Hash? (readonly)

Server capabilities from initialize response

Returns:

  • Server capabilities



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# File 'lib/mcp_client/server_streamable_http.rb', line 37

def capabilities
  @capabilities
end

#endpoint ⇒ String (readonly)

Returns The JSON-RPC endpoint path.

Returns:

  • The JSON-RPC endpoint path



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# File 'lib/mcp_client/server_streamable_http.rb', line 29

attr_reader :base_url, :endpoint, :tools

#server_info ⇒ Hash? (readonly)

Server information from initialize response

Returns:

  • Server information



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# File 'lib/mcp_client/server_streamable_http.rb', line 33

def server_info
  @server_info
end

#tools ⇒ Object (readonly)

Returns the value of attribute tools.



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# File 'lib/mcp_client/server_streamable_http.rb', line 29

attr_reader :base_url, :endpoint, :tools

Instance Method Details

#apply_request_headers(req, request) ⇒ Object

Override apply_request_headers to add session and SSE headers for MCP protocol



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# File 'lib/mcp_client/server_streamable_http.rb', line 195

def apply_request_headers(req, request)
  super

  # Add session header if we have one (for non-initialize requests)
  if @session_id && request['method'] != 'initialize'
    req.headers['Mcp-Session-Id'] = @session_id
    @logger.debug("Adding session header: Mcp-Session-Id: #{@session_id}")
  end

  # Add Last-Event-ID header for resumability (if available)
  return unless @last_event_id

  req.headers['Last-Event-ID'] = @last_event_id
  @logger.debug("Adding Last-Event-ID header: #{@last_event_id}")
end

#call_tool(tool_name, parameters) ⇒ Object

Call a tool with the given parameters

Parameters:

  • the name of the tool to call

  • the parameters to pass to the tool

Returns:

  • the result of the tool invocation (with string keys for backward compatibility)

Raises:

  • if server returns an error

  • if response isn’t valid JSON

  • for other errors during tool execution

  • if server is disconnected



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# File 'lib/mcp_client/server_streamable_http.rb', line 171

def call_tool(tool_name, parameters)
  rpc_request('tools/call', {
                name: tool_name,
                arguments: parameters
              })
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError
  # Re-raise connection/transport errors directly to match test expectations
  raise
rescue StandardError => e
  # For all other errors, wrap in ToolCallError
  raise MCPClient::Errors::ToolCallError, "Error calling tool '#{tool_name}': #{e.message}"
end

#call_tool_streaming(tool_name, parameters) ⇒ Enumerator

Stream tool call (default implementation returns single-value stream)

Parameters:

  • the name of the tool to call

  • the parameters to pass to the tool

Returns:

  • stream of results



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# File 'lib/mcp_client/server_streamable_http.rb', line 188

def call_tool_streaming(tool_name, parameters)
  Enumerator.new do |yielder|
    yielder << call_tool(tool_name, parameters)
  end
end

#cleanup ⇒ Object

Clean up the server connection Properly closes HTTP connections and clears cached state



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# File 'lib/mcp_client/server_streamable_http.rb', line 243

def cleanup
  @mutex.synchronize do
    # Attempt to terminate session before cleanup
    terminate_session if @session_id

    @connection_established = false
    @initialized = false

    @logger.debug('Cleaning up Streamable HTTP connection')

    # Close HTTP connection if it exists
    @http_conn = nil
    @session_id = nil

    @tools = nil
    @tools_data = nil
  end
end

#connect ⇒ Boolean

Connect to the MCP server over Streamable HTTP

Returns:

  • true if connection was successful

Raises:

  • if connection fails



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# File 'lib/mcp_client/server_streamable_http.rb', line 104

def connect
  return true if @mutex.synchronize { @connection_established }

  begin
    @mutex.synchronize do
      @connection_established = false
      @initialized = false
    end

    # Test connectivity with a simple HTTP request
    test_connection

    # Perform MCP initialization handshake
    perform_initialize

    @mutex.synchronize do
      @connection_established = true
      @initialized = true
    end

    true
  rescue MCPClient::Errors::ConnectionError => e
    cleanup
    raise e
  rescue StandardError => e
    cleanup
    raise MCPClient::Errors::ConnectionError, "Failed to connect to MCP server at #{@base_url}: #{e.message}"
  end
end

#handle_successful_response(response, request) ⇒ Object

Override handle_successful_response to capture session ID



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# File 'lib/mcp_client/server_streamable_http.rb', line 212

def handle_successful_response(response, request)
  super

  # Capture session ID from initialize response with validation
  return unless request['method'] == 'initialize' && response.success?

  session_id = response.headers['mcp-session-id'] || response.headers['Mcp-Session-Id']
  if session_id
    if valid_session_id?(session_id)
      @session_id = session_id
      @logger.debug("Captured session ID: #{@session_id}")
    else
      @logger.warn("Invalid session ID format received: #{session_id.inspect}")
    end
  else
    @logger.warn('No session ID found in initialize response headers')
  end
end

#list_tools ⇒ Array<MCPClient::Tool>

List all tools available from the MCP server

Returns:

  • list of available tools

Raises:

  • if server returns an error

  • if response isn’t valid JSON

  • for other errors during tool listing



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# File 'lib/mcp_client/server_streamable_http.rb', line 139

def list_tools
  @mutex.synchronize do
    return @tools if @tools
  end

  begin
    ensure_connected

    tools_data = request_tools_list
    @mutex.synchronize do
      @tools = tools_data.map do |tool_data|
        MCPClient::Tool.from_json(tool_data, server: self)
      end
    end

    @mutex.synchronize { @tools }
  rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
    # Re-raise these errors directly
    raise
  rescue StandardError => e
    raise MCPClient::Errors::ToolCallError, "Error listing tools: #{e.message}"
  end
end

#terminate_session ⇒ Boolean

Terminate the current session (if any)

Returns:

  • true if termination was successful or no session exists



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# File 'lib/mcp_client/server_streamable_http.rb', line 233

def terminate_session
  @mutex.synchronize do
    return true unless @session_id

    super
  end
end