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 (MCP 2025-06-18) This transport uses HTTP POST for RPC calls with optional SSE responses, and GET for event streams Compliant with MCP specification version 2025-06-18

Key features:

  • Supports server-sent events (SSE) for real-time notifications

  • Handles ping/pong keepalive mechanism

  • Thread-safe connection management

  • Automatic reconnection with exponential backoff

Defined Under Namespace

Modules: JsonRpcTransport

Constant Summary collapse

DEFAULT_READ_TIMEOUT =

Default values for connection settings

30
DEFAULT_MAX_RETRIES = 
3
SSE_CONNECTION_TIMEOUT =

SSE connection settings

300
SSE_RECONNECT_DELAY =

5 minutes

1
SSE_MAX_RECONNECT_DELAY =

Initial reconnect delay in seconds

30
THREAD_JOIN_TIMEOUT =

Maximum reconnect delay in seconds

5

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:

  • base_url (String) —

    The base URL of the MCP server

  • options (Hash) —

    Server configuration options (same as ServerHTTP)

Raises:

  • (ArgumentError) 


54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
 
# File 'lib/mcp_client/server_streamable_http.rb', line 54

def initialize(base_url:, **options)
  opts = default_options.merge(options)
  super(name: opts[:name])
  initialize_logger(opts[:logger])

  @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',
                                    'User-Agent' => "ruby-mcp-client/#{MCPClient::VERSION}",
                                    'Cache-Control' => 'no-cache'
                                  })

  @read_timeout = opts[:read_timeout]
  @faraday_config = opts[:faraday_config]
  @tools = nil
  @tools_data = nil
  @prompts = nil
  @prompts_data = nil
  @resources = nil
  @resources_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]

  # SSE events connection state
  @events_connection = nil
  @events_thread = nil
  @buffer = '' # Buffer for partial SSE event data
  @elicitation_request_callback = nil # MCP 2025-06-18
  @roots_list_request_callback = nil # MCP 2025-06-18
  @sampling_request_callback = nil # MCP 2025-06-18
end

Instance Attribute Details

#base_url ⇒ String (readonly)

Returns The base URL of the MCP server.

Returns:

  • (String) —

    The base URL of the MCP server



42
43
44
 
# File 'lib/mcp_client/server_streamable_http.rb', line 42

def base_url
  @base_url
end

#capabilities ⇒ Hash? (readonly)

Server capabilities from initialize response

Returns:

  • (Hash, nil) —

    Server capabilities



50
51
52
 
# File 'lib/mcp_client/server_streamable_http.rb', line 50

def capabilities
  @capabilities
end

#endpoint ⇒ String (readonly)

Returns The JSON-RPC endpoint path.

Returns:

  • (String) —

    The JSON-RPC endpoint path



42
 
# File 'lib/mcp_client/server_streamable_http.rb', line 42

attr_reader :base_url, :endpoint, :tools

#server_info ⇒ Hash? (readonly)

Server information from initialize response

Returns:

  • (Hash, nil) —

    Server information



46
47
48
 
# File 'lib/mcp_client/server_streamable_http.rb', line 46

def server_info
  @server_info
end

#tools ⇒ Object (readonly)

Returns the value of attribute tools.



42
 
# File 'lib/mcp_client/server_streamable_http.rb', line 42

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



393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
 
# File 'lib/mcp_client/server_streamable_http.rb', line 393

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:

  • tool_name (String) —

    the name of the tool to call

  • parameters (Hash) —

    the parameters to pass to the tool

Returns:

  • (Object) —

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

Raises:



198
199
200
201
202
203
204
205
206
207
208
209
210
 
# File 'lib/mcp_client/server_streamable_http.rb', line 198

def call_tool(tool_name, parameters)
  rpc_request('tools/call', {
                name: tool_name,
                arguments: parameters.except(:_meta),
                **parameters.slice(:_meta)
              })
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:

  • tool_name (String) —

    the name of the tool to call

  • parameters (Hash) —

    the parameters to pass to the tool

Returns:

  • (Enumerator) —

    stream of results



216
217
218
219
220
 
# File 'lib/mcp_client/server_streamable_http.rb', line 216

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, stops threads, and clears cached state



441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
 
# File 'lib/mcp_client/server_streamable_http.rb', line 441

def cleanup
  @mutex.synchronize do
    return unless @connection_established || @initialized

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

    # Mark connection as closed to stop reconnection attempts
    @connection_established = false
    @initialized = false

    # Attempt to terminate session before cleanup
    begin
      terminate_session if @session_id
    rescue StandardError => e
      @logger.warn("Failed to terminate session: #{e.message}")
    end

    # Stop events thread gracefully
    if @events_thread&.alive?
      @logger.debug('Stopping events thread...')
      @events_thread.kill
      @events_thread.join(THREAD_JOIN_TIMEOUT)
    end
    @events_thread = nil

    # Clear connections and state
    @http_conn = nil
    @events_connection = nil
    @session_id = nil
    @last_event_id = nil

    # Clear cached data
    @tools = nil
    @tools_data = nil
    @prompts = nil
    @prompts_data = nil
    @resources = nil
    @resources_data = nil
    @buffer = ''

    @logger.info('Cleanup completed')
  end
end

#complete(ref:, argument:) ⇒ Hash

Request completion suggestions from the server (MCP 2025-06-18)

Parameters:

  • ref (Hash) —

    reference object (e.g., { ‘type’ => ‘ref/prompt’, ‘name’ => ‘prompt_name’ })

  • argument (Hash) —

    the argument being completed (e.g., { ‘name’ => ‘arg_name’, ‘value’ => ‘partial’ })

Returns:

  • (Hash) —

    completion result with ‘values’, optional ‘total’, and ‘hasMore’ fields

Raises:



227
228
229
230
231
232
233
234
 
# File 'lib/mcp_client/server_streamable_http.rb', line 227

def complete(ref:, argument:)
  result = rpc_request('completion/complete', { ref: ref, argument: argument })
  result['completion'] || { 'values' => [] }
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ServerError, "Error requesting completion: #{e.message}"
end

#connect ⇒ Boolean

Connect to the MCP server over Streamable HTTP

Returns:

  • (Boolean) —

    true if connection was successful

Raises:



128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
 
# File 'lib/mcp_client/server_streamable_http.rb', line 128

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

    # Start long-lived GET connection for server events
    start_events_connection

    @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

#get_prompt(prompt_name, parameters) ⇒ Object

Get a prompt with the given parameters

Parameters:

  • prompt_name (String) —

    the name of the prompt to get

  • parameters (Hash) —

    the parameters to pass to the prompt

Returns:

  • (Object) —

    the result of the prompt (with string keys for backward compatibility)

Raises:



281
282
283
284
285
286
287
288
289
290
291
292
293
 
# File 'lib/mcp_client/server_streamable_http.rb', line 281

def get_prompt(prompt_name, parameters)
  rpc_request('prompts/get', {
                name: prompt_name,
                arguments: parameters.except(:_meta),
                **parameters.slice(:_meta)
              })
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError
  # Re-raise connection/transport errors directly
  raise
rescue StandardError => e
  # For all other errors, wrap in PromptGetError
  raise MCPClient::Errors::PromptGetError, "Error getting prompt '#{prompt_name}': #{e.message}"
end

#handle_successful_response(response, request) ⇒ Object

Override handle_successful_response to capture session ID



410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
 
# File 'lib/mcp_client/server_streamable_http.rb', line 410

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_prompts ⇒ Array<MCPClient::Prompt>

List all prompts available from the MCP server

Returns:

Raises:



252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
 
# File 'lib/mcp_client/server_streamable_http.rb', line 252

def list_prompts
  @mutex.synchronize do
    return @prompts if @prompts
  end

  begin
    ensure_connected

    prompts_data = request_prompts_list
    @mutex.synchronize do
      @prompts = prompts_data.map do |prompt_data|
        MCPClient::Prompt.from_json(prompt_data, server: self)
      end
    end

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

#list_resource_templates(cursor: nil) ⇒ Hash

List all resource templates available from the MCP server

Parameters:

  • cursor (String, nil) (defaults to: nil) —

    optional cursor for pagination

Returns:

  • (Hash) —

    result containing resourceTemplates array and optional nextCursor

Raises:



350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
 
# File 'lib/mcp_client/server_streamable_http.rb', line 350

def list_resource_templates(cursor: nil)
  params = {}
  params['cursor'] = cursor if cursor
  result = rpc_request('resources/templates/list', params)

  templates = (result['resourceTemplates'] || []).map do |template_data|
    MCPClient::ResourceTemplate.from_json(template_data, server: self)
  end

  { 'resourceTemplates' => templates, 'nextCursor' => result['nextCursor'] }
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ResourceReadError, "Error listing resource templates: #{e.message}"
end

#list_resources(cursor: nil) ⇒ Hash

List all resources available from the MCP server

Parameters:

  • cursor (String, nil) (defaults to: nil) —

    optional cursor for pagination

Returns:

  • (Hash) —

    result containing resources array and optional nextCursor

Raises:



299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
 
# File 'lib/mcp_client/server_streamable_http.rb', line 299

def list_resources(cursor: nil)
  @mutex.synchronize do
    return @resources_result if @resources_result && !cursor
  end

  begin
    ensure_connected

    params = {}
    params['cursor'] = cursor if cursor
    result = rpc_request('resources/list', params)

    resources = (result['resources'] || []).map do |resource_data|
      MCPClient::Resource.from_json(resource_data, server: self)
    end

    resources_result = { 'resources' => resources, 'nextCursor' => result['nextCursor'] }

    @mutex.synchronize do
      @resources_result = resources_result unless cursor
    end

    resources_result
  rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
    # Re-raise these errors directly
    raise
  rescue StandardError => e
    raise MCPClient::Errors::ResourceReadError, "Error listing resources: #{e.message}"
  end
end

#list_tools ⇒ Array<MCPClient::Tool>

List all tools available from the MCP server

Returns:

Raises:



166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
 
# File 'lib/mcp_client/server_streamable_http.rb', line 166

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

#log_level=(level) ⇒ Hash

Set the logging level on the server (MCP 2025-06-18)

Parameters:

  • level (String) —

    the log level (‘debug’, ‘info’, ‘notice’, ‘warning’, ‘error’, ‘critical’, ‘alert’, ‘emergency’)

Returns:

  • (Hash) —

    empty result on success

Raises:



241
242
243
244
245
246
247
 
# File 'lib/mcp_client/server_streamable_http.rb', line 241

def log_level=(level)
  rpc_request('logging/setLevel', { level: level })
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ServerError, "Error setting log level: #{e.message}"
end

#on_elicitation_request(&block) ⇒ void

This method returns an undefined value.

Register a callback for elicitation requests (MCP 2025-06-18)

Parameters:

  • block (Proc) —

    callback that receives (request_id, params) and returns response hash



488
489
490
 
# File 'lib/mcp_client/server_streamable_http.rb', line 488

def on_elicitation_request(&block)
  @elicitation_request_callback = block
end

#on_roots_list_request(&block) ⇒ void

This method returns an undefined value.

Register a callback for roots/list requests (MCP 2025-06-18)

Parameters:

  • block (Proc) —

    callback that receives (request_id, params) and returns response hash



495
496
497
 
# File 'lib/mcp_client/server_streamable_http.rb', line 495

def on_roots_list_request(&block)
  @roots_list_request_callback = block
end

#on_sampling_request(&block) ⇒ void

This method returns an undefined value.

Register a callback for sampling requests (MCP 2025-06-18)

Parameters:

  • block (Proc) —

    callback that receives (request_id, params) and returns response hash



502
503
504
 
# File 'lib/mcp_client/server_streamable_http.rb', line 502

def on_sampling_request(&block)
  @sampling_request_callback = block
end

#read_resource(uri) ⇒ Array<MCPClient::ResourceContent>

Read a resource by its URI

Parameters:

  • uri (String) —

    the URI of the resource to read

Returns:

Raises:



334
335
336
337
338
339
340
341
342
343
344
 
# File 'lib/mcp_client/server_streamable_http.rb', line 334

def read_resource(uri)
  result = rpc_request('resources/read', { uri: uri })
  contents = result['contents'] || []
  contents.map { |content| MCPClient::ResourceContent.from_json(content) }
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError
  # Re-raise connection/transport errors directly
  raise
rescue StandardError => e
  # For all other errors, wrap in ResourceReadError
  raise MCPClient::Errors::ResourceReadError, "Error reading resource '#{uri}': #{e.message}"
end

#subscribe_resource(uri) ⇒ Boolean

Subscribe to resource updates

Parameters:

  • uri (String) —

    the URI of the resource to subscribe to

Returns:

  • (Boolean) —

    true if subscription successful

Raises:



370
371
372
373
374
375
376
377
 
# File 'lib/mcp_client/server_streamable_http.rb', line 370

def subscribe_resource(uri)
  rpc_request('resources/subscribe', { uri: uri })
  true
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ResourceReadError, "Error subscribing to resource '#{uri}': #{e.message}"
end

#terminate_session ⇒ Boolean

Terminate the current session (if any)

Returns:

  • (Boolean) —

    true if termination was successful or no session exists



431
432
433
434
435
436
437
 
# File 'lib/mcp_client/server_streamable_http.rb', line 431

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

    super
  end
end

#unsubscribe_resource(uri) ⇒ Boolean

Unsubscribe from resource updates

Parameters:

  • uri (String) —

    the URI of the resource to unsubscribe from

Returns:

  • (Boolean) —

    true if unsubscription successful

Raises:



383
384
385
386
387
388
389
390
 
# File 'lib/mcp_client/server_streamable_http.rb', line 383

def unsubscribe_resource(uri)
  rpc_request('resources/unsubscribe', { uri: uri })
  true
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ResourceReadError, "Error unsubscribing from resource '#{uri}': #{e.message}"
end