docs(client): improve server reliability and error handling #560
Conversation
- Add a health check step using Ping to verify server availability - Change error handling for listing tools and resources to terminate the program on failure Signed-off-by: Bo-Yi Wu <[email protected]>
WalkthroughAdds a post-initialization health check via Ping(ctx) in the sample client and changes error handling for ListTools and ListResources from non-fatal logging to fatal exits on errors. Changes
Estimated code review effort🎯 2 (Simple) | ⏱️ ~10 minutes Possibly related PRs
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Actionable comments posted: 1
🧹 Nitpick comments (1)
examples/simple_client/main.go (1)
151-156: Refactor error handling for client cleanup and drop redundant pagination note
The client’s
ListResourcesmethod already aggregates pages internally (seeclient/client.go:243–265), so no manual pagination loop is needed.Introduce a
fatalfhelper inexamples/simple_client/main.goto close the client before exiting:// Add just after imports: func fatalf(c *client.Client, format string, args ...interface{}) { c.Close() log.Fatalf(format, args...) }Replace the
log.Fatalfcall on ListResources error (line 151) withfatalf(c, ...):- if err != nil { - log.Fatalf("Failed to list resources: %v", err) - } + if err != nil { + fatalf(c, "Failed to list resources: %v", err) + }Optionally, add
defer c.Close()immediately after initializingc(in the stdio/http branches) to ensure cleanup on normal exit paths.
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📒 Files selected for processing (1)
examples/simple_client/main.go(2 hunks)
🧰 Additional context used
🧠 Learnings (1)
📚 Learning: 2025-06-30T07:13:17.052Z
Learnt from: ezynda3
PR: mark3labs/mcp-go#461
File: server/sampling.go:22-26
Timestamp: 2025-06-30T07:13:17.052Z
Learning: In the mark3labs/mcp-go project, the MCPServer.capabilities field is a struct value (serverCapabilities), not a pointer, so it cannot be nil and doesn't require nil checking. Only pointer fields within the capabilities struct should be checked for nil.
Applied to files:
examples/simple_client/main.go
🧬 Code graph analysis (1)
examples/simple_client/main.go (1)
mcp/tools.go (1)
ListToolsRequest(18-21)
🔇 Additional comments (1)
examples/simple_client/main.go (1)
137-142: I’ve requested the example’s main.go context and checked for any existingfatalfhelper. Once we have that, I can confirm how to best implement cleanup on errors and finalize the review.
| // Perform health check using ping | ||
| fmt.Println("Performing health check...") | ||
| if err := c.Ping(ctx); err != nil { | ||
| log.Fatalf("❌ Health check failed: %v", err) | ||
| } | ||
| fmt.Println("✅ Server is alive and responding") | ||
|
|
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🛠️ Refactor suggestion
Graceful teardown before fatal exit to avoid leaking the server process (stdio) or sockets (HTTP).
log.Fatalf calls os.Exit(1), so defers won’t run and c.Close() won’t execute. If the stdio client has already started the server process, this can orphan it; for HTTP it can leave connections unclosed. Close the client explicitly before exiting.
Apply this diff in place:
- if err := c.Ping(ctx); err != nil {
- log.Fatalf("❌ Health check failed: %v", err)
- }
+ if err := c.Ping(ctx); err != nil {
+ fatalf(c, "❌ Health check failed: %v", err)
+ }Additionally (optional): use a short ping timeout and a couple of retries with backoff to reduce flakiness when a server is still warming up.
Supporting helper to add elsewhere in this file:
// fatalf closes the client (best-effort) before exiting fatally.
func fatalf(c *client.Client, format string, args ...any) {
if c != nil {
_ = c.Close()
}
log.Fatalf(format, args...)
}🤖 Prompt for AI Agents
In examples/simple_client/main.go around lines 124 to 130, the health-check uses
log.Fatalf which exits immediately and prevents defers (including c.Close())
from running; replace the fatal call with a helper that closes the client before
exiting (add a small fatalf(c *client.Client, format string, args ...any) helper
that best-effort calls c.Close() then calls log.Fatalf), update the Ping error
path to call fatalf(c, "...", err) instead of log.Fatalf, and optionally
implement a short context timeout and a couple of retry attempts with
exponential backoff around c.Ping to reduce flakiness while the server is
warming up.
| if err := c.Ping(ctx); err != nil { | ||
| log.Fatalf("❌ Health check failed: %v", err) | ||
| } | ||
| fmt.Println("✅ Server is alive and responding") |
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it’s better to remove the ❌ and ✅ icons since they may not display correctly in all environments.
Description
Type of Change
Checklist
MCP Spec Compliance
Additional Information
Summary by CodeRabbit
New Features
Refactor