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fix: don't share mutex between tools/resources #574

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Merged
merged 1 commit into from
Sep 11, 2025
Merged

fix: don't share mutex between tools/resources #574

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19 changes: 10 additions & 9 deletions server/server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -147,9 +147,10 @@ type NotificationHandlerFunc func(ctx context.Context, notification mcp.JSONRPCN
type MCPServer struct {
// Separate mutexes for different resource types
resourcesMu sync.RWMutex
resourceMiddlewareMu sync.RWMutex
promptsMu sync.RWMutex
toolsMu sync.RWMutex
middlewareMu sync.RWMutex
toolMiddlewareMu sync.RWMutex
notificationHandlersMu sync.RWMutex
capabilitiesMu sync.RWMutex
toolFiltersMu sync.RWMutex
Expand Down Expand Up @@ -221,9 +222,9 @@ func WithToolHandlerMiddleware(
toolHandlerMiddleware ToolHandlerMiddleware,
) ServerOption {
return func(s *MCPServer) {
s.middlewareMu.Lock()
s.toolMiddlewareMu.Lock()
s.toolHandlerMiddlewares = append(s.toolHandlerMiddlewares, toolHandlerMiddleware)
s.middlewareMu.Unlock()
s.toolMiddlewareMu.Unlock()
}
}

Expand All @@ -233,9 +234,9 @@ func WithResourceHandlerMiddleware(
resourceHandlerMiddleware ResourceHandlerMiddleware,
) ServerOption {
return func(s *MCPServer) {
s.middlewareMu.Lock()
s.resourceMiddlewareMu.Lock()
s.resourceHandlerMiddlewares = append(s.resourceHandlerMiddlewares, resourceHandlerMiddleware)
s.middlewareMu.Unlock()
s.resourceMiddlewareMu.Unlock()
}
}

Expand Down Expand Up @@ -876,13 +877,13 @@ func (s *MCPServer) handleReadResource(
s.resourcesMu.RUnlock()

finalHandler := handler
s.middlewareMu.RLock()
s.resourceMiddlewareMu.RLock()
mw := s.resourceHandlerMiddlewares
// Apply middlewares in reverse order
for i := len(mw) - 1; i >= 0; i-- {
finalHandler = mw[i](finalHandler)
}
s.middlewareMu.RUnlock()
s.resourceMiddlewareMu.RUnlock()

contents, err := finalHandler(ctx, request)
if err != nil {
Expand Down Expand Up @@ -1138,14 +1139,14 @@ func (s *MCPServer) handleToolCall(

finalHandler := tool.Handler

s.middlewareMu.RLock()
s.toolMiddlewareMu.RLock()
mw := s.toolHandlerMiddlewares

// Apply middlewares in reverse order
for i := len(mw) - 1; i >= 0; i-- {
finalHandler = mw[i](finalHandler)
}
s.middlewareMu.RUnlock()
s.toolMiddlewareMu.RUnlock()

result, err := finalHandler(ctx, request)
if err != nil {
Expand Down