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fix(mcp): make readiness probe non-invasive #151

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113 changes: 5 additions & 108 deletions internal/daemon/daemon.go
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,16 +1,11 @@
package daemon

import (
"bufio"
"bytes"
"context"
"encoding/json"
"errors"
"fmt"
"io"
"log"
"net"
"net/http"
"net/url"
"strings"
"sync"
Expand Down Expand Up @@ -61,8 +56,6 @@ const (
SDKClaude = "claude"
)

const mcpProbeID = "agynd-mcp-ready"

type Daemon struct {
cfg config.Config
sdk string
Expand Down Expand Up @@ -848,7 +841,6 @@ type tcpServiceTarget struct {
type mcpServiceTarget struct {
label string
addr string
url string
}

func waitForTCPService(ctx context.Context, addr string, timeout time.Duration, label string) error {
Expand Down Expand Up @@ -891,7 +883,6 @@ func waitForMCPServers(ctx context.Context, servers []config.MCPServer, timeout
targets = append(targets, mcpServiceTarget{
label: fmt.Sprintf("MCP server %s", server.Name),
addr: addr,
url: mcpEndpoint(server.Port),
})
}
return waitForMCPServices(ctx, targets, timeout)
Expand All @@ -907,12 +898,11 @@ func waitForMCPServices(ctx context.Context, targets []mcpServiceTarget, timeout
}
deadline := time.NewTimer(timeout)
defer deadline.Stop()
client := &http.Client{Timeout: 10 * time.Second}
for _, target := range targets {
attempt := 0
for {
attempt++
if err := probeMCPService(ctx, client, target.url); err == nil {
if err := probeMCPService(ctx, target.addr); err == nil {
log.Printf("%s at %s ready after %d attempt(s)", target.label, target.addr, attempt)
break
} else {
Expand All @@ -930,106 +920,13 @@ func waitForMCPServices(ctx context.Context, targets []mcpServiceTarget, timeout
return nil
}

func probeMCPService(ctx context.Context, client *http.Client, endpoint string) error {
body := []byte(fmt.Sprintf(`{"jsonrpc":"2.0","id":%q,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"agynd","version":"mcp-ready"}}}`, mcpProbeID))
req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, bytes.NewReader(body))
func probeMCPService(ctx context.Context, addr string) error {
dialer := net.Dialer{Timeout: 1 * time.Second}
conn, err := dialer.DialContext(ctx, "tcp", addr)
if err != nil {
return err
}
req.Header.Set("Content-Type", "application/json")
req.Header.Set("Accept", "application/json, text/event-stream")
resp, err := client.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode < 200 || resp.StatusCode >= 300 {
return fmt.Errorf("http status %s", resp.Status)
}
return readMCPProbeResult(resp.Body)
}

type mcpProbeResponse struct {
JSONRPC string `json:"jsonrpc"`
ID string `json:"id"`
Result json.RawMessage `json:"result"`
Error json.RawMessage `json:"error"`
}

func readMCPProbeResult(body io.Reader) error {
reader := bufio.NewReader(io.LimitReader(body, 64*1024))
var raw bytes.Buffer
var eventData []string
var lastEventErr error
sawSSE := false

for {
line, err := reader.ReadString('\n')
if line != "" {
raw.WriteString(line)
trimmed := strings.TrimRight(line, "\r\n")
if data, ok := strings.CutPrefix(trimmed, "data:"); ok {
sawSSE = true
eventData = append(eventData, strings.TrimSpace(data))
} else if sawSSE && strings.TrimSpace(trimmed) == "" {
if len(eventData) > 0 {
if err := validateMCPProbePayload([]byte(strings.Join(eventData, "\n"))); err == nil {
return nil
} else {
lastEventErr = err
}
}
eventData = nil
}
}
if err == nil {
continue
}
if errors.Is(err, io.EOF) {
break
}
return err
}

if sawSSE {
if len(eventData) > 0 {
if err := validateMCPProbePayload([]byte(strings.Join(eventData, "\n"))); err == nil {
return nil
} else {
lastEventErr = err
}
}
if lastEventErr != nil {
return lastEventErr
}
return fmt.Errorf("initialize SSE response missing data")
}
return validateMCPProbePayload(raw.Bytes())
}

func validateMCPProbePayload(payload []byte) error {
payload = bytes.TrimSpace(payload)
if len(payload) == 0 {
return fmt.Errorf("initialize response is empty")
}
var response mcpProbeResponse
if err := json.Unmarshal(payload, &response); err != nil {
return fmt.Errorf("parse initialize response: %w", err)
}
if response.JSONRPC != "2.0" {
return fmt.Errorf("initialize response jsonrpc %q does not match 2.0", response.JSONRPC)
}
if response.ID != mcpProbeID {
return fmt.Errorf("initialize response id %q does not match %q", response.ID, mcpProbeID)
}
if len(bytes.TrimSpace(response.Error)) > 0 && !bytes.Equal(bytes.TrimSpace(response.Error), []byte("null")) {
return fmt.Errorf("initialize response contains error")
}
result := bytes.TrimSpace(response.Result)
if len(result) == 0 || bytes.Equal(result, []byte("null")) {
return fmt.Errorf("initialize response missing result")
}
return nil
return conn.Close()
}

type codexThreadDefaults struct {
Expand Down
134 changes: 41 additions & 93 deletions internal/daemon/daemon_mcp_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,20 +3,19 @@ package daemon
import (
"context"
"errors"
"fmt"
"net"
"net/http"
"strings"
"sync/atomic"
"testing"
"time"

"github.com/agynio/agynd-cli/internal/config"
)

func TestWaitForMCPServersReady(t *testing.T) {
_, portA := startMCPReadyServer(t)
_, portB := startMCPReadyServer(t)
listenerA, portA := startAcceptingTCPListener(t)
defer listenerA.Close()
listenerB, portB := startAcceptingTCPListener(t)
defer listenerB.Close()

ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
defer cancel()
Expand All @@ -30,75 +29,42 @@ func TestWaitForMCPServersReady(t *testing.T) {
}
}

func TestWaitForMCPServersWaitsForInitializeResponse(t *testing.T) {
var requests atomic.Int32
server := &http.Server{Handler: http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
attempt := requests.Add(1)
if attempt < 3 {
http.Error(w, "starting", http.StatusServiceUnavailable)
func TestWaitForMCPServersDoesNotSendInitialize(t *testing.T) {
readBytes := make(chan int, 1)
listener, port := startTCPListener(t)
defer listener.Close()

go func() {
conn, err := listener.Accept()
if err != nil {
return
}
_, _ = w.Write([]byte(`{"jsonrpc":"2.0","id":"agynd-mcp-ready","result":{"protocolVersion":"2025-06-18"}}`))
})}
listener, port := startHTTPListener(t, server)
defer listener.Close()
defer conn.Close()

ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
if err := conn.SetReadDeadline(time.Now().Add(100 * time.Millisecond)); err != nil {
readBytes <- -1
return
}
buf := make([]byte, 1)
n, _ := conn.Read(buf)
readBytes <- n
}()

ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
defer cancel()

servers := []config.MCPServer{{Name: "memory", Port: port}}
if err := waitForMCPServers(ctx, servers, 5*time.Second); err != nil {
t.Fatalf("expected MCP server to become ready, got %v", err)
}
if got := requests.Load(); got < 3 {
t.Fatalf("expected readiness probe retries, got %d request(s)", got)
}
}

func TestReadMCPProbeResultRejectsInvalidPayloads(t *testing.T) {
tests := []struct {
name string
payload string
}{
{
name: "json rpc error containing result text",
payload: `{"jsonrpc":"2.0","id":"agynd-mcp-ready","error":{"message":"no result yet"}}`,
},
{
name: "unrelated payload containing result text",
payload: `{"message":"result is almost ready"}`,
},
{
name: "wrong response id",
payload: `{"jsonrpc":"2.0","id":"other","result":{"protocolVersion":"2025-06-18"}}`,
},
{
name: "null result",
payload: `{"jsonrpc":"2.0","id":"agynd-mcp-ready","result":null}`,
},
}

for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
if err := readMCPProbeResult(strings.NewReader(tt.payload)); err == nil {
t.Fatal("expected invalid MCP initialize response to be rejected")
}
})
if err := waitForMCPServers(ctx, servers, 500*time.Millisecond); err != nil {
t.Fatalf("expected MCP listener to be ready, got %v", err)
}
}

func TestReadMCPProbeResultAcceptsSSEInitializeResult(t *testing.T) {
payload := strings.Join([]string{
`event: message`,
`data: {"jsonrpc":"2.0","id":"unrelated","result":{"protocolVersion":"2025-06-18"}}`,
``,
`event: message`,
`data: {"jsonrpc":"2.0","id":"agynd-mcp-ready","result":{"protocolVersion":"2025-06-18"}}`,
``,
}, "\n")

if err := readMCPProbeResult(strings.NewReader(payload)); err != nil {
t.Fatalf("expected SSE initialize result to be accepted, got %v", err)
select {
case got := <-readBytes:
if got != 0 {
t.Fatalf("expected readiness probe to send no payload, got %d byte(s)", got)
}
case <-time.After(500 * time.Millisecond):
t.Fatal("listener did not observe readiness connection")
}
}

Expand Down Expand Up @@ -150,37 +116,19 @@ func startTCPListener(t *testing.T) (net.Listener, int) {
return listener, addr.Port
}

func startMCPReadyServer(t *testing.T) (*http.Server, int) {
func startAcceptingTCPListener(t *testing.T) (net.Listener, int) {
t.Helper()
server := &http.Server{Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r.URL.Path != "/mcp" {
http.NotFound(w, r)
return
}
_, _ = w.Write([]byte(`{"jsonrpc":"2.0","id":"agynd-mcp-ready","result":{"protocolVersion":"2025-06-18"}}`))
})}
listener, port := startHTTPListener(t, server)
t.Cleanup(func() { _ = listener.Close() })
return server, port
}

func startHTTPListener(t *testing.T, server *http.Server) (net.Listener, int) {
t.Helper()
listener, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
t.Fatalf("listen: %v", err)
}
addr, ok := listener.Addr().(*net.TCPAddr)
if !ok {
_ = listener.Close()
t.Fatalf("unexpected listener address type %T", listener.Addr())
}
listener, port := startTCPListener(t)
go func() {
if err := server.Serve(listener); err != nil && !errors.Is(err, http.ErrServerClosed) && !strings.Contains(err.Error(), "use of closed network connection") {
panic(fmt.Sprintf("serve MCP ready test server: %v", err))
for {
conn, err := listener.Accept()
if err != nil {
return
}
_ = conn.Close()
}
}()
return listener, addr.Port
return listener, port
}

func unusedTCPPort(t *testing.T) int {
Expand Down
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