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internal/mcp: implement streamable HTTP transport

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Add an (almost) complete implementation of the streamable HTTP
transport, including:
- A StreamableHTTPHandler for serving sessions.
- A StreamableHTTPServerTransport that supports session resumption.
- A minimal StreamableHTTPClientTransport.

Additionally, include the following minor changes:
- Refactor SSE event reading to use an iterator.
- Start to to aliases for JSON-RPC types (incomplete)
- Fix handling for null tool arguments (again)

Still to do:
- The streamable client does not support retry/resumption, or the
  side-channel GET requests.
- Support configurable session and event retention (garbage collection).
- Expose the HTTP client used for HTTP requests (for auth).

Change-Id: Ieba216ef901169b4660d601386fa0c7c7bb4c4b2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/667515
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Rob Findley 2025-04-23 10:52:44 +00:00 • committed by Robert Findley
commit d2f2f87bbe
1 changed files with 1570 additions and 149 deletions
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18
examples/hello/main.go
View file

@ -8,6 +8,7 @@ import (
"context"
"flag"
"fmt"
"log"
"net/http"
"net/url"
"os"
@ -15,21 +16,23 @@ import (
"github.com/modelcontextprotocol/go-sdk/mcp"
)
var httpAddr = flag.String("http", "", "if set, use SSE HTTP at this address, instead of stdin/stdout")
var httpAddr = flag.String("http", "", "if set, use streamable HTTP at this address, instead of stdin/stdout")
type HiArgs struct {
Name string `json:"name"`
}
func SayHi(ctx context.Context, ss *mcp.ServerSession, params *mcp.CallToolParamsFor[HiArgs]) (*mcp.CallToolResultFor[any], error) {
return &mcp.CallToolResultFor[any]{
func SayHi(ctx context.Context, ss *mcp.ServerSession, params *mcp.CallToolParamsFor[HiArgs]) (*mcp.CallToolResultFor[struct{}], error) {
return &mcp.CallToolResultFor[struct{}]{
Content: []*mcp.Content{
mcp.NewTextContent("Hi " + params.Name),
},
}, nil
}
func PromptHi(ctx context.Context, ss *mcp.ServerSession, args *HiArgs, params *mcp.GetPromptParams) (*mcp.GetPromptResult, error) {
// TODO(jba): it should be OK for args to be a pointer, but this fails in
// jsonschema. Needs investigation.
func PromptHi(ctx context.Context, ss *mcp.ServerSession, args HiArgs, params *mcp.GetPromptParams) (*mcp.GetPromptResult, error) {
return &mcp.GetPromptResult{
Description: "Code review prompt",
Messages: []*mcp.PromptMessage{
@ -56,14 +59,15 @@ func main() {
})
if *httpAddr != "" {
handler := mcp.NewSSEHandler(func(*http.Request) *mcp.Server {
handler := mcp.NewStreamableHTTPHandler(func(*http.Request) *mcp.Server {
return server
})
}, nil)
log.Printf("MCP handler listening at %s", *httpAddr)
http.ListenAndServe(*httpAddr, handler)
} else {
t := mcp.NewLoggingTransport(mcp.NewStdIOTransport(), os.Stderr)
if err := server.Run(context.Background(), t); err != nil {
fmt.Fprintf(os.Stderr, "Server failed: %v", err)
log.Printf("Server failed: %v", err)
}
}
}