Bcain99 Fixes

[bcain99]

• Fixed bug where mcp sse client was not re-using connections for the /message endpoint (due to not draining io)
• Added http client transport parameters for client keepalives
• Fixed bug where handleListTools was not releasing mutex

Summary by CodeRabbit

• Bug Fixes
  • Improved connection reuse and response handling for HTTP requests, enhancing reliability and performance.
  • Fixed an issue where a server read lock was not properly released during tool listing, preventing potential resource contention.

[coderabbitai]

Walkthrough

This change updates the HTTP client configuration and response body handling in the SSE client implementation. The HTTP client is now initialized with a custom transport that optimizes connection reuse parameters. Additionally, the response body in the sendRequest method is fully read into memory and closed explicitly, improving resource management and error reporting. On the server side, a missing call to release a read lock is added in the handleListTools method to ensure proper synchronization.

Changes

Files/Paths	Change Summary
client/sse.go	Updated HTTP client initialization with a custom transport for better connection reuse; improved response body handling in sendRequest by reading and closing the body explicitly, enhancing error reporting and resource management.
server/server.go	Added a missing call to release a read lock (RUnlock) in the handleListTools method to ensure correct synchronization.

Possibly related PRs

• mark3labs/mcp-go#88: Also modifies client/sse.go, focusing on removing the SSE read timeout feature to fix client hangs; related by file and component.
• mark3labs/mcp-go#55: Updates client/sse.go to add configurable headers and read timeout options, directly modifying the sendRequest method and client setup, making it closely related.

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📜 Recent review details

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Review profile: CHILL
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📥 Commits

Reviewing files that changed from the base of the PR and between 8cdb6c6 and f6c405d.

📒 Files selected for processing (2)

• client/sse.go (2 hunks)
• server/server.go (1 hunks)

🔇 Additional comments (3)

server/server.go (1)

798-799: Great fix for the missed mutex unlock!

This change correctly adds the missing s.mu.RUnlock() after collecting and sorting the tools. It ensures the read lock is released as soon as it's no longer needed, before pagination and returning the result. Without this fix, the read lock would be held for longer than necessary, potentially causing performance issues or deadlocks if other parts of the code needed to acquire a write lock.

client/sse.go (2)

59-67: Excellent improvement to the HTTP client configuration for connection reuse.

Replacing the default HTTP client with a custom one that has specified connection pool parameters is a great optimization for an SSE client. The configuration now:

• Allows up to 100 idle connections in the pool
• Limits to 10 idle connections per host
• Sets a reasonable 90-second timeout for idle connections
• Explicitly enables keepalives

This will significantly improve connection reuse for frequent client-server communication.

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314-320: Good fix for proper response body handling.

This change properly drains the response body, which is essential for connection reuse in HTTP clients. The code now:

1. Reads the entire body with io.ReadAll()
2. Closes the body immediately after reading
3. Returns an error if reading fails
4. Includes the response body text in error messages

This ensures that connections can be properly reused, fixing the bug where connections weren't being reused for the /message endpoint.

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[tylergannon]

Might make sense to implement this as a WithTransport(*http.Transport) option, rather than hard-coding the settings?

[StarpTech]

@bcain99 could you add a test?