geektutu/7days-golang · warning

bad request

Error message

bad request

What it means

geecache's HTTPPool.ServeHTTP only understands URLs of the form /<basePath>/<groupName>/<key>. When the path after basePath splits on '/' into fewer than 2 segments, it responds with HTTP 400 and body 'bad request'. It is the library telling you the request URL does not match the expected cache API shape.

Source

Thrown at gee-cache/day3-http-server/geecache/http.go:41

		basePath: defaultBasePath,
	}
}

// Log info with server name
func (p *HTTPPool) Log(format string, v ...interface{}) {
	log.Printf("[Server %s] %s", p.self, fmt.Sprintf(format, v...))
}

// ServeHTTP handle all http requests
func (p *HTTPPool) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if !strings.HasPrefix(r.URL.Path, p.basePath) {
		panic("HTTPPool serving unexpected path: " + r.URL.Path)
	}
	p.Log("%s %s", r.Method, r.URL.Path)
	// /<basepath>/<groupname>/<key> required
	parts := strings.SplitN(r.URL.Path[len(p.basePath):], "/", 2)
	if len(parts) != 2 {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}

	groupName := parts[0]
	key := parts[1]

	group := GetGroup(groupName)
	if group == nil {
		http.Error(w, "no such group: "+groupName, http.StatusNotFound)
		return
	}

	view, err := group.Get(key)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

View on GitHub (pinned to cf36443821)

Solutions

1. Send the full expected path: /<basePath>/<groupName>/<key>, e.g. GET /_geecache/groups/key1.
2. Exclude this endpoint from health checks, or point health checks at a dedicated route (e.g. /healthz) served by a different handler.
3. Check any reverse-proxy/ingress rewrite rules so they do not strip the group or key segment.
4. URL-encode the key if it can contain '/' so SplitN still yields exactly two parts.

Example fix

// before: GET /_geecache/mygroup  -> 400
http.Get("http://localhost:8001/_geecache/mygroup")
// after: include key
http.Get("http://localhost:8001/_geecache/mygroup/key1")

// validate the URL before calling the cache node
func validCacheURL(base, group, key string) bool {
    return group != "" && key != "" && !strings.ContainsAny(key, "/?#")
}
// url := base + "/" + group + "/" + url.PathEscape(key)

When it happens

Trigger: An HTTP request to the pool whose path after basePath contains fewer than two '/'-separated parts, e.g. GET /_geecache/ or GET /_geecache/mygroup (missing the /<key> segment).

Common situations: Health checks or load balancers hitting the pool's base path directly; a client forgetting to append /<key>; proxy rewriting that strips part of the path; typos like a trailing-slash-only URL.

Related errors

• bad request
• bad request
• key is required
• no such group: "+groupName
• err.Error()

AI-assisted analysis of geektutu/7days-golang@cf36443821 (2026-09-03). Data as JSON: /api/errors/8be1527df24247a6. Report an issue: GitHub.