fix: handle the situation where the channel is closed #304

button-chen · 2025-05-19T08:11:10Z

Description

This PR fix handle the situation where the channel is closed.

When using mcp-go as the mcp client, sometimes it is necessary to use ping to keep the server alive. A goroutine will be started to send pings at intervals. When an error is detected in the ping return, the client will be shut down. At this point, if other goroutines are using this client, a crash will occur. The reason is that the response is nil, which will be in the code:

// mcp-go code
if response.Error ! = nil {   // panic occurred, because response is nil
    return nil, errors.New(response.Error.Message)
}

// my code
go func() {
......
for {
	select {
	case <-ticker.C:
		err := c.Ping(ctx)
		if err != nil {
			cli.c.Close()
			return
		}
	}
}
}()

Type of Change

Bug fix (non-breaking change that fixes an issue)
New feature (non-breaking change that adds functionality)
MCP spec compatibility implementation
Breaking change (fix or feature that would cause existing functionality to not work as expected)
Documentation update
Code refactoring (no functional changes)
Performance improvement
Tests only (no functional changes)
Other (please describe):

Checklist

My code follows the code style of this project
I have performed a self-review of my own code
I have added tests that prove my fix is effective or that my feature works
I have updated the documentation accordingly

MCP Spec Compliance

This PR implements a feature defined in the MCP specification
Link to relevant spec section: Link text
Implementation follows the specification exactly

Additional Information

coderabbitai · 2025-05-19T08:11:17Z

Walkthrough

The change updates the logic in the SendRequest method within the SSE transport client to explicitly handle cases where the response channel is closed before a response is received, returning an error in such scenarios. No exported or public entity signatures were altered.

Changes

File(s)	Change Summary
client/transport/sse.go	Updated `SendRequest` to check if the response channel is closed and return an error if so.

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🔧 golangci-lint (1.64.8)

Error: you are using a configuration file for golangci-lint v2 with golangci-lint v1: please use golangci-lint v2
Failed executing command with error: you are using a configuration file for golangci-lint v2 with golangci-lint v1: please use golangci-lint v2

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📥 Commits

Reviewing files that changed from the base of the PR and between eaa6f29 and b2e4e31.

📒 Files selected for processing (1)

client/transport/sse.go (1 hunks)

🔇 Additional comments (1)

client/transport/sse.go (1)

313-317: Fixed potential panic on closed channel.

The change correctly handles the case where the response channel is closed, preventing a panic that would occur if code attempted to access fields of a nil response. This is a standard Go pattern for safely consuming from a channel.

This implementation directly addresses the PR's goal of fixing a crash that occurs when the client is shut down while other goroutines are still using it.

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fix: handle the situation where the channel is closed

b2e4e31

ezynda3 merged commit 99720bb into mark3labs:main May 19, 2025
4 checks passed

coderabbitai bot mentioned this pull request Jul 16, 2025

fix: check if resp is nil on error for initialize methods #492

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fix: handle the situation where the channel is closed #304

fix: handle the situation where the channel is closed #304

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button-chen commented May 19, 2025 •

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fix: handle the situation where the channel is closed #304

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button-chen commented May 19, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Description

Type of Change

Checklist

MCP Spec Compliance

Additional Information

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button-chen commented May 19, 2025 •

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