t8y2/dbx · error

ZooKeeper connect string contains no servers

Error message

ZooKeeper connect string contains no servers

What it means

parseConnectTarget splits the ZooKeeper connect string on commas into host:port server entries (with an optional chroot path). If, after trimming, no server entries remain, it returns 'ZooKeeper connect string contains no servers'.

Source

Thrown at agents/drivers/zookeeper/connection.go:376

func parseConnectTarget(value string) (connectTarget, error) {
	connectString := strings.TrimSpace(strings.TrimPrefix(value, "zookeeper://"))
	slash := strings.Index(connectString, "/")
	hostsPart := connectString
	chroot := ""
	if slash >= 0 {
		hostsPart = connectString[:slash]
		chroot = normalizePrefix(connectString[slash:])
	}
	servers := make([]string, 0)
	for _, item := range strings.Split(hostsPart, ",") {
		server := strings.TrimSpace(item)
		if server != "" {
			servers = append(servers, server)
		}
	}
	if len(servers) == 0 {
		return connectTarget{}, errors.New("ZooKeeper connect string contains no servers")
	}
	return connectTarget{Servers: servers, Chroot: chroot}, nil
}

func requireReachableServer(servers []string, timeout time.Duration) error {
	ctx, cancel := context.WithTimeout(context.Background(), timeout+500*time.Millisecond)
	defer cancel()
	workers := minInt(len(servers), maximumReachabilityWorkers)
	jobs := make(chan string)
	reachable := make(chan struct{}, 1)
	var waitGroup sync.WaitGroup
	for worker := 0; worker < workers; worker++ {
		waitGroup.Add(1)
		go func() {
			defer waitGroup.Done()
			for server := range jobs {
				address, err := endpointAddress(server)
				if err != nil {

View on GitHub (pinned to c0390bff16)

Solutions

1. Set the connect string to at least one host:port, e.g. "zk1:2181,zk2:2181" (optionally with chroot: "zk1:2181/app/ns").
2. Check the config source (env var, config file, secret) is actually populated at runtime — log or print the resolved value.
3. Fix templating/escaping issues that dropped the server list.
4. Validate the config early with TestConnectionConfiguration before opening the client.

Example fix

// before
config.ConnectString = ""
// after
config.ConnectString = "zk1:2181,zk2:2181"

func validateConnectString(s string) error {
    if strings.TrimSpace(s) == "" { return errors.New("zookeeper connect string is empty") }
    for _, item := range strings.Split(s, ",") {
        item = strings.TrimSpace(item)
        if item != "" && strings.Contains(item, ":") { return nil }
    }
    return errors.New("zookeeper connect string has no host:port servers")
}
// call before openClient / TestConnectionConfiguration

if err := validateConnectString(cfg.ConnectString); err != nil {
    return fmt.Errorf("bad zookeeper config: %w", err)
}
session, err := openClient(cfg)
if err != nil { return err }

When it happens

Trigger: Calling openClient, TestConnectionConfiguration, or databaseInfo with a connect string that is empty, whitespace-only, consists only of separators, or is just a chroot path with no host:port entries before it. Raised in agents/drivers/zookeeper/connection.go:376.

Common situations: Config env var or YAML key missing/empty so the connect string is ""; a typo leaving only "/chroot" in the field; template/secret expansion yielding whitespace; trailing commas producing zero non-empty items.

Related errors

• ZooKeeper server list is empty
• Unsupported auth_scheme %q; expected %q or %q
• base_sleep_time_ms must be non-negative
• max_retries must be non-negative
• %s must be between 1 and %d bytes

AI-assisted analysis of t8y2/dbx@c0390bff16 (2026-09-05). Data as JSON: /api/errors/cf5d7c8b4f235307. Report an issue: GitHub.