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Merged
merged 5 commits into from
Apr 14, 2025
Merged

Dustin/138 deadlock remove global mutex #139

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2352335
fix: remove global mutex
StarpTech Apr 13, 2025
24a4bba
chore: remove uncessary comments
StarpTech Apr 13, 2025
fd3fc67
chore: remove comment
StarpTech Apr 13, 2025
8d5b20c
chore: remove comment
StarpTech Apr 13, 2025
8815f14
chore: explicit err checks
StarpTech Apr 13, 2025
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96 changes: 63 additions & 33 deletions server/server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -141,7 +141,14 @@ type NotificationHandlerFunc func(ctx context.Context, notification mcp.JSONRPCN
// MCPServer implements a Model Control Protocol server that can handle various types of requests
// including resources, prompts, and tools.
type MCPServer struct {
mu sync.RWMutex // Add mutex for protecting shared resources
// Separate mutexes for different resource types
resourcesMu sync.RWMutex
promptsMu sync.RWMutex
toolsMu sync.RWMutex
middlewareMu sync.RWMutex
notificationHandlersMu sync.RWMutex
capabilitiesMu sync.RWMutex

name string
version string
instructions string
Expand Down Expand Up @@ -301,7 +308,9 @@ func WithToolHandlerMiddleware(
toolHandlerMiddleware ToolHandlerMiddleware,
) ServerOption {
return func(s *MCPServer) {
s.middlewareMu.Lock()
s.toolHandlerMiddlewares = append(s.toolHandlerMiddlewares, toolHandlerMiddleware)
s.middlewareMu.Unlock()
}
}

Expand Down Expand Up @@ -396,11 +405,14 @@ func (s *MCPServer) AddResource(
resource mcp.Resource,
handler ResourceHandlerFunc,
) {
s.capabilitiesMu.Lock()
if s.capabilities.resources == nil {
s.capabilities.resources = &resourceCapabilities{}
}
s.mu.Lock()
defer s.mu.Unlock()
s.capabilitiesMu.Unlock()

s.resourcesMu.Lock()
defer s.resourcesMu.Unlock()
s.resources[resource.URI] = resourceEntry{
resource: resource,
handler: handler,
Expand All @@ -412,11 +424,14 @@ func (s *MCPServer) AddResourceTemplate(
template mcp.ResourceTemplate,
handler ResourceTemplateHandlerFunc,
) {
s.capabilitiesMu.Lock()
if s.capabilities.resources == nil {
s.capabilities.resources = &resourceCapabilities{}
}
s.mu.Lock()
defer s.mu.Unlock()
s.capabilitiesMu.Unlock()

s.resourcesMu.Lock()
defer s.resourcesMu.Unlock()
s.resourceTemplates[template.URITemplate.Raw()] = resourceTemplateEntry{
template: template,
handler: handler,
Expand All @@ -425,11 +440,14 @@ func (s *MCPServer) AddResourceTemplate(

// AddPrompt registers a new prompt handler with the given name
func (s *MCPServer) AddPrompt(prompt mcp.Prompt, handler PromptHandlerFunc) {
s.capabilitiesMu.Lock()
if s.capabilities.prompts == nil {
s.capabilities.prompts = &promptCapabilities{}
}
s.mu.Lock()
defer s.mu.Unlock()
s.capabilitiesMu.Unlock()

s.promptsMu.Lock()
defer s.promptsMu.Unlock()
s.prompts[prompt.Name] = prompt
s.promptHandlers[prompt.Name] = handler
}
Expand All @@ -441,34 +459,37 @@ func (s *MCPServer) AddTool(tool mcp.Tool, handler ToolHandlerFunc) {

// AddTools registers multiple tools at once
func (s *MCPServer) AddTools(tools ...ServerTool) {
s.capabilitiesMu.Lock()
if s.capabilities.tools == nil {
s.capabilities.tools = &toolCapabilities{}
}
s.mu.Lock()
s.capabilitiesMu.Unlock()

s.toolsMu.Lock()
for _, entry := range tools {
s.tools[entry.Tool.Name] = entry
}
s.mu.Unlock()
s.toolsMu.Unlock()

// Send notification to all initialized sessions
s.sendNotificationToAllClients("notifications/tools/list_changed", nil)
}

// SetTools replaces all existing tools with the provided list
func (s *MCPServer) SetTools(tools ...ServerTool) {
s.mu.Lock()
s.toolsMu.Lock()
s.tools = make(map[string]ServerTool)
s.mu.Unlock()
s.toolsMu.Unlock()
s.AddTools(tools...)
}

// DeleteTools removes a tool from the server
func (s *MCPServer) DeleteTools(names ...string) {
s.mu.Lock()
s.toolsMu.Lock()
for _, name := range names {
delete(s.tools, name)
}
s.mu.Unlock()
s.toolsMu.Unlock()

// Send notification to all initialized sessions
s.sendNotificationToAllClients("notifications/tools/list_changed", nil)
Expand All @@ -479,8 +500,8 @@ func (s *MCPServer) AddNotificationHandler(
method string,
handler NotificationHandlerFunc,
) {
s.mu.Lock()
defer s.mu.Unlock()
s.notificationHandlersMu.Lock()
defer s.notificationHandlersMu.Unlock()
s.notificationHandlers[method] = handler
}

Expand Down Expand Up @@ -589,12 +610,12 @@ func (s *MCPServer) handleListResources(
id interface{},
request mcp.ListResourcesRequest,
) (*mcp.ListResourcesResult, *requestError) {
s.mu.RLock()
s.resourcesMu.RLock()
resources := make([]mcp.Resource, 0, len(s.resources))
for _, entry := range s.resources {
resources = append(resources, entry.resource)
}
s.mu.RUnlock()
s.resourcesMu.RUnlock()

// Sort the resources by name
sort.Slice(resources, func(i, j int) bool {
Expand Down Expand Up @@ -622,12 +643,12 @@ func (s *MCPServer) handleListResourceTemplates(
id interface{},
request mcp.ListResourceTemplatesRequest,
) (*mcp.ListResourceTemplatesResult, *requestError) {
s.mu.RLock()
s.resourcesMu.RLock()
templates := make([]mcp.ResourceTemplate, 0, len(s.resourceTemplates))
for _, entry := range s.resourceTemplates {
templates = append(templates, entry.template)
}
s.mu.RUnlock()
s.resourcesMu.RUnlock()
sort.Slice(templates, func(i, j int) bool {
return templates[i].Name < templates[j].Name
})
Expand All @@ -653,11 +674,11 @@ func (s *MCPServer) handleReadResource(
id interface{},
request mcp.ReadResourceRequest,
) (*mcp.ReadResourceResult, *requestError) {
s.mu.RLock()
s.resourcesMu.RLock()
// First try direct resource handlers
if entry, ok := s.resources[request.Params.URI]; ok {
handler := entry.handler
s.mu.RUnlock()
s.resourcesMu.RUnlock()
contents, err := handler(ctx, request)
if err != nil {
return nil, &requestError{
Expand Down Expand Up @@ -686,7 +707,7 @@ func (s *MCPServer) handleReadResource(
break
}
}
s.mu.RUnlock()
s.resourcesMu.RUnlock()

if matched {
contents, err := matchedHandler(ctx, request)
Expand Down Expand Up @@ -717,12 +738,12 @@ func (s *MCPServer) handleListPrompts(
id interface{},
request mcp.ListPromptsRequest,
) (*mcp.ListPromptsResult, *requestError) {
s.mu.RLock()
s.promptsMu.RLock()
prompts := make([]mcp.Prompt, 0, len(s.prompts))
for _, prompt := range s.prompts {
prompts = append(prompts, prompt)
}
s.mu.RUnlock()
s.promptsMu.RUnlock()

// sort prompts by name
sort.Slice(prompts, func(i, j int) bool {
Expand Down Expand Up @@ -750,9 +771,9 @@ func (s *MCPServer) handleGetPrompt(
id interface{},
request mcp.GetPromptRequest,
) (*mcp.GetPromptResult, *requestError) {
s.mu.RLock()
s.promptsMu.RLock()
handler, ok := s.promptHandlers[request.Params.Name]
s.mu.RUnlock()
s.promptsMu.RUnlock()

if !ok {
return nil, &requestError{
Expand All @@ -779,7 +800,7 @@ func (s *MCPServer) handleListTools(
id interface{},
request mcp.ListToolsRequest,
) (*mcp.ListToolsResult, *requestError) {
s.mu.RLock()
s.toolsMu.RLock()
tools := make([]mcp.Tool, 0, len(s.tools))

// Get all tool names for consistent ordering
Expand All @@ -795,6 +816,8 @@ func (s *MCPServer) handleListTools(
for _, name := range toolNames {
tools = append(tools, s.tools[name].Tool)
}
s.toolsMu.RUnlock()

toolsToReturn, nextCursor, err := listByPagination[mcp.Tool](ctx, s, request.Params.Cursor, tools)
if err != nil {
return nil, &requestError{
Expand All @@ -817,9 +840,9 @@ func (s *MCPServer) handleToolCall(
id interface{},
request mcp.CallToolRequest,
) (*mcp.CallToolResult, *requestError) {
s.mu.RLock()
s.toolsMu.RLock()
tool, ok := s.tools[request.Params.Name]
s.mu.RUnlock()
s.toolsMu.RUnlock()

if !ok {
return nil, &requestError{
Expand All @@ -830,9 +853,16 @@ func (s *MCPServer) handleToolCall(
}

finalHandler := tool.Handler
for i := len(s.toolHandlerMiddlewares) - 1; i >= 0; i-- {
finalHandler = s.toolHandlerMiddlewares[i](finalHandler)

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

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

result, err := finalHandler(ctx, request)
if err != nil {
return nil, &requestError{
Expand All @@ -849,9 +879,9 @@ func (s *MCPServer) handleNotification(
ctx context.Context,
notification mcp.JSONRPCNotification,
) mcp.JSONRPCMessage {
s.mu.RLock()
s.notificationHandlersMu.RLock()
handler, ok := s.notificationHandlers[notification.Method]
s.mu.RUnlock()
s.notificationHandlersMu.RUnlock()

if ok {
handler(ctx, notification)
Expand Down
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