Class: RailsAiContext::McpController

Inherits:
ActionController::API
  • Object
show all
Includes:
ActionController::Live
Defined in:
app/controllers/rails_ai_context/mcp_controller.rb

Overview

Rails controller for serving MCP over Streamable HTTP. Alternative to the Rack middleware - integrates with Rails routing, authentication, and middleware stack.

Mount in routes: mount RailsAiContext::Engine, at: "/mcp"

Defined Under Namespace

Classes: FlushableStream

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.mcp_transport ⇒ Object

Class-level memoization - transport persists across requests. Thread-safe: MCP::Server and transport are stateless for reads.



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# File 'app/controllers/rails_ai_context/mcp_controller.rb', line 84

def mcp_transport
  @transport_mutex.synchronize do
    @mcp_transport ||= begin
      server = RailsAiContext::Server.new(Rails.application, transport: :http).build
      MCP::Server::Transports::StreamableHTTPTransport.new(server)
    end
  end
end

.reset_transport! ⇒ Object 



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# File 'app/controllers/rails_ai_context/mcp_controller.rb', line 93

def reset_transport!
  @transport_mutex.synchronize { @mcp_transport = nil }
end

Instance Method Details

#handle ⇒ Object 



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# File 'app/controllers/rails_ai_context/mcp_controller.rb', line 29

def handle
  status_code, rack_headers, body = self.class.mcp_transport.handle_request(request)
  self.status = status_code
  rack_headers.each { |k, v| response.headers[k] = v }

  if body.respond_to?(:each)
    # Plain enumerable body (initialize, errors, JSON mode): join to a
    # string so Content-Length/ETag semantics stay conventional.
    chunks = []
    body.each { |chunk| chunks << chunk }
    body.close if body.respond_to?(:close)
    self.response_body = chunks.join
  elsif body.respond_to?(:call)
    stream = response.stream
    stream = FlushableStream.new(stream) unless stream.respond_to?(:flush)
    begin
      body.call(stream)
      # A GET opens the server-push channel: the transport registers the
      # stream and returns, expecting it to outlive this call. Live closes
      # the response when the action returns, so hold the thread until the
      # transport's keepalive (or the client) closes the stream. Live also
      # sends headers only on the first write - the transport writes
      # nothing until its first keepalive ping, so commit with an SSE
      # comment up front or clients sit waiting on headers.
      if request.get?
        begin
          stream.write(": connected\n\n")
        rescue IOError
          nil
        end
        wait_for_stream_close
      end
    ensure
      begin
        response.stream.close
      rescue StandardError
        nil
      end
    end
  else
    self.response_body = body
  end
end