perf(server): release Mutex early for performance

[cryo-zd]

  Note that in func MCPServer.AddResource()/AddResourceTemplate()/AddPrompt(), we utilize defer s.resourcesMu.Unlock() / defer s.promptsMu.Unlock() to release the corresponding exclusive mutex, which makes the functions mentioned could only release the mutex after we finish calling func SendNotificationToAllClients() to send notifications to all clients connected to MCPServer. And this could be a bottleneck in concurrent scenario when there are too many clients and there are also too many request of calling func AddResource() / AddResourceTemplate() /AddPrompt()

Is it safe to release the mutex as soon as we finish modifying s.resources/s.resourceTemplates/s.prompts but don't wait func SendNotificationToAllClients to finish?
  I think the answer to this question is YES, because func SendNotificationToAllClients only iterates over all registered sessions and send notifications to them, it doesn't modify s.resources/s.resourceTemplates/s.prompts and even don't read these fields.

//func (s *MCPServer) SendNotificationToAllClients()
	s.sessions.Range(func(k, v any) bool {
		if session, ok := v.(ClientSession); ok && session.Initialized() {
			select {
			case session.NotificationChannel() <- notification:
			default:
				// TODO: log blocked channel in the future versions
			}
		}
		return true
	})

experiment

Summary by CodeRabbit

• Refactor
  • Improved internal locking mechanism for better efficiency during resource and prompt updates. No changes to user-facing functionality.

[coderabbitai]

Walkthrough

This change updates the locking mechanism in three methods of the MCPServer implementation: AddResource, AddResourceTemplate, and AddPrompt. Instead of using deferred statements to unlock mutexes at the end of each method, the code now explicitly unlocks the mutex immediately after the critical section that modifies shared maps. No changes were made to the method signatures or the logic outside of mutex handling.

Changes

File(s)	Change Summary
server/server.go	Replaced deferred mutex unlocks with explicit unlock calls after map mutations in three methods: AddResource, AddResourceTemplate, and AddPrompt. No changes to method signatures or other logic.

Possibly related PRs

• fix race conditions #31: Introduces broader synchronization and atomic operations for thread safety in MCPServer, including changes to locking in the same methods.
• perf: optimize usage of RWMutex in MCPServer for performance #181: Optimizes locking strategy in MCPServer methods with a focus on the capabilitiesMu RWMutex, similar in scope but targeting a different mutex.
• Dustin/138 deadlock remove global mutex #139: Replaces a global mutex with multiple granular mutexes in MCPServer, laying the groundwork for the refined locking pattern in this PR.

---

📜 Recent review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 33c98f1 and bde7c06.

📒 Files selected for processing (1)

• server/server.go (3 hunks)

🔇 Additional comments (4)

server/server.go (4)

428-428: Improved performance by releasing the mutex earlier.

The mutex is now explicitly unlocked immediately after modifying the shared resource, rather than using a deferred unlock. This reduces lock contention by releasing the exclusive lock before SendNotificationToAllClients() executes.

---

473-473: Improved performance by releasing the mutex earlier.

Similar to the change in AddResource(), the mutex is now explicitly unlocked immediately after modifying the shared resource template map. This reduces lock contention since SendNotificationToAllClients() doesn't require access to the protected resources.

---

500-500: Improved performance by releasing the mutex earlier.

The mutex is now explicitly unlocked immediately after updating the prompts and promptHandlers maps. This change reduces lock contention since SendNotificationToAllClients() doesn't need to access these protected resources.

---

216-241: Confirms the safety of earlier mutex unlock.

This method only iterates over the sessions map and sends notifications through client channels without accessing the resources protected by resourcesMu or promptsMu, confirming that unlocking those mutexes earlier is safe.

✨ Finishing Touches

• 📝 Generate Docstrings

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

🪧 Tips

Chat

There are 3 ways to chat with CodeRabbit:

• Review comments: Directly reply to a review comment made by CodeRabbit. Example:
  • I pushed a fix in commit <commit_id>, please review it.
  • Generate unit testing code for this file.
  • Open a follow-up GitHub issue for this discussion.
• Files and specific lines of code (under the "Files changed" tab): Tag @coderabbitai in a new review comment at the desired location with your query. Examples:
  • @coderabbitai generate unit testing code for this file.
  • @coderabbitai modularize this function.
• PR comments: Tag @coderabbitai in a new PR comment to ask questions about the PR branch. For the best results, please provide a very specific query, as very limited context is provided in this mode. Examples:
  • @coderabbitai gather interesting stats about this repository and render them as a table. Additionally, render a pie chart showing the language distribution in the codebase.
  • @coderabbitai read src/utils.ts and generate unit testing code.
  • @coderabbitai read the files in the src/scheduler package and generate a class diagram using mermaid and a README in the markdown format.
  • @coderabbitai help me debug CodeRabbit configuration file.

Note: Be mindful of the bot's finite context window. It's strongly recommended to break down tasks such as reading entire modules into smaller chunks. For a focused discussion, use review comments to chat about specific files and their changes, instead of using the PR comments.

CodeRabbit Commands (Invoked using PR comments)

• @coderabbitai pause to pause the reviews on a PR.
• @coderabbitai resume to resume the paused reviews.
• @coderabbitai review to trigger an incremental review. This is useful when automatic reviews are disabled for the repository.
• @coderabbitai full review to do a full review from scratch and review all the files again.
• @coderabbitai summary to regenerate the summary of the PR.
• @coderabbitai generate docstrings to generate docstrings for this PR.
• @coderabbitai generate sequence diagram to generate a sequence diagram of the changes in this PR.
• @coderabbitai resolve resolve all the CodeRabbit review comments.
• @coderabbitai configuration to show the current CodeRabbit configuration for the repository.
• @coderabbitai help to get help.

Other keywords and placeholders

• Add @coderabbitai ignore anywhere in the PR description to prevent this PR from being reviewed.
• Add @coderabbitai summary to generate the high-level summary at a specific location in the PR description.
• Add @coderabbitai anywhere in the PR title to generate the title automatically.

CodeRabbit Configuration File (.coderabbit.yaml)

• You can programmatically configure CodeRabbit by adding a .coderabbit.yaml file to the root of your repository.
• Please see the configuration documentation for more information.
• If your editor has YAML language server enabled, you can add the path at the top of this file to enable auto-completion and validation: # yaml-language-server: $schema=https://coderabbit.ai/integrations/schema.v2.json

Documentation and Community

• Visit our Documentation for detailed information on how to use CodeRabbit.
• Join our Discord Community to get help, request features, and share feedback.
• Follow us on X/Twitter for updates and announcements.

[dugenkui03]

lgtm