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[Doc] Restructure README Usage section to align heading granularity

Browse source 
Group the Rails (mount) and Rails (controller) examples under a new
`Streamable HTTP Transport` heading so they sit one level below the
transport-type headings instead of alongside `Stdio Transport`.

Also move the single-process and sticky-sessions caveat up to the
`Streamable HTTP Transport` section since it applies to both Rails
integration styles rather than only the controller approach.
This commit is contained in:
Koichi ITO 2026-04-15 14:30:52 +09:00
commit acdf85f039
1 changed files with 25 additions and 14 deletions
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README.md
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@ -104,7 +104,24 @@ $ ruby examples/stdio_server.rb
{"jsonrpc":"2.0","id":"3","method":"tools/call","params":{"name":"example_tool","arguments":{"message":"Hello"}}} {"jsonrpc":"2.0","id":"3","method":"tools/call","params":{"name":"example_tool","arguments":{"message":"Hello"}}}
``` ```
#### Rails (mount) #### Streamable HTTP Transport
`MCP::Server::Transports::StreamableHTTPTransport` is a standard Rack app, so it can be mounted in any Rack-compatible framework.
The following examples show two common integration styles in Rails.
> [!IMPORTANT]
> `MCP::Server::Transports::StreamableHTTPTransport` stores session and SSE stream state in memory,
> so it must run in a single process. Use a single-process server (e.g., Puma with `workers 0`).
> Multi-process configurations (Unicorn, or Puma with `workers > 0`) fork separate processes that
> do not share memory, which breaks session management and SSE connections.
>
> When running multiple server instances behind a load balancer, configure your load balancer to use
> sticky sessions (session affinity) so that requests with the same `Mcp-Session-Id` header are always
> routed to the same instance.
>
> Stateless mode (`stateless: true`) does not use sessions and works with any server configuration.
##### Rails (mount)
`StreamableHTTPTransport` is a Rack app that can be mounted directly in Rails routes: `StreamableHTTPTransport` is a Rack app that can be mounted directly in Rails routes:
@ -125,7 +142,13 @@ Rails.application.routes.draw do
end end
``` ```
#### Rails (controller) `mount` directs all HTTP methods on `/mcp` to the transport. `StreamableHTTPTransport` internally dispatches
`POST` (client-to-server JSON-RPC messages, with responses optionally streamed via SSE),
`GET` (optional standalone SSE stream for server-to-client messages), and `DELETE` (session termination) per
the [MCP Streamable HTTP transport spec](https://modelcontextprotocol.io/specification/latest/basic/transports#streamable-http),
so no additional route configuration is needed.
##### Rails (controller)
While the mount approach creates a single server at boot time, the controller approach creates a new server per request. While the mount approach creates a single server at boot time, the controller approach creates a new server per request.
This allows you to customize tools, prompts, or configuration based on the request (e.g., different tools per route). This allows you to customize tools, prompts, or configuration based on the request (e.g., different tools per route).
@ -153,18 +176,6 @@ class McpController < ActionController::API
end end
``` ```
> [!IMPORTANT]
> `MCP::Server::Transports::StreamableHTTPTransport` stores session and SSE stream state in memory,
> so it must run in a single process. Use a single-process server (e.g., Puma with `workers 0`).
> Multi-process configurations (Unicorn, or Puma with `workers > 0`) fork separate processes that
> do not share memory, which breaks session management and SSE connections.
>
> When running multiple server instances behind a load balancer, configure your load balancer to use
> sticky sessions (session affinity) so that requests with the same `Mcp-Session-Id` header are always
> routed to the same instance.
>
> Stateless mode (`stateless: true`) does not use sessions and works with any server configuration.
### Configuration ### Configuration
The gem can be configured using the `MCP.configure` block: The gem can be configured using the `MCP.configure` block: