apache/dolphinscheduler · error · RegistryException

zookeeper check key is existed error

Error message

zookeeper check key is existed error

What it means

ZookeeperRegistry.exists() calls Curator's client.checkExists().forPath(key) and wraps any exception in a RegistryException with message 'zookeeper check key is existed error'. Unlike get(), a missing node is not an error here (null Stat is returned as false); the wrapper fires only on infrastructure or argument failures.

Source

Thrown at dolphinscheduler-registry/dolphinscheduler-registry-plugins/dolphinscheduler-registry-zookeeper/src/main/java/org/apache/dolphinscheduler/plugin/registry/zookeeper/ZookeeperRegistry.java:167

            throw new RegistryException("Failed to subscribe listener for key: " + path, e);
        }
    }

    @Override
    public String get(String key) {
        try {
            return new String(client.getData().forPath(key), StandardCharsets.UTF_8);
        } catch (Exception e) {
            throw new RegistryException("zookeeper get data error", e);
        }
    }

    @Override
    public boolean exists(String key) {
        try {
            return null != client.checkExists().forPath(key);
        } catch (Exception e) {
            throw new RegistryException("zookeeper check key is existed error", e);
        }
    }

    @Override
    public void put(String key, String value, boolean deleteOnDisconnect) {
        final CreateMode mode = deleteOnDisconnect ? CreateMode.EPHEMERAL : CreateMode.PERSISTENT;

        try {
            client.create()
                    .orSetData()
                    .creatingParentsIfNeeded()
                    .withMode(mode)
                    .forPath(key, value.getBytes(StandardCharsets.UTF_8));
        } catch (Exception e) {
            throw new RegistryException("Failed to put registry key: " + key, e);
        }
    }

View on GitHub (pinned to 02eac45a1b)

Solutions

1. Check the wrapped cause: KeeperException.Code CONNECTIONLOSS/SESSIONEXPIRED → verify ensemble health and wait for Curator session recovery, then retry
2. Validate the key is an absolute, well-formed ZNode path before calling
3. Verify registry.zookeeper.connect-string, chroot, and auth configuration in the DolphinScheduler common properties
4. Check ZooKeeper server logs and ACLs if AUTHFAILED/NOAUTH appears

Example fix

// before
String key = "/ds/" + id;
boolean ok = registry.exists(key);
// after
if (id == null || id.isEmpty()) { throw new IllegalArgumentException("id required"); }
boolean ok = registry.exists("/ds/" + id);

if (key == null || !key.startsWith("/")) {
    throw new IllegalArgumentException("registry key must be an absolute znode path");
}

try {
    return registry.exists(key);
} catch (RegistryException e) {
    Throwable cause = e.getCause();
    if (cause instanceof KeeperException.ConnectionLossException || cause instanceof KeeperException.SessionExpiredException) {
        return retryExists(key); // retry after session recovery
    }
    throw e;
}

When it happens

Trigger: Calling exists(key) while the ZooKeeper session is expired or the ensemble is unreachable (CONNECTIONLOSS), when the key is a malformed path (empty string, not starting with '/', contains null byte — BADARGUMENTS), or when ACLs deny the checkExists stat call.

Common situations: ZooKeeper cluster down or network partition during startup health checks; building keys from user-supplied IDs that produce invalid paths; misconfigured chroot or connect string so all paths resolve outside the allowed tree.

Understand the failure class

Background: ECONNREFUSED and "connection refused" / "could not connect to server" errors: what they mean and how to fix them — this error's family across 44 libraries.

Related errors

• Failed to subscribe listener for key:
• zookeeper get data error
• Failed to put registry key:
• zookeeper get children error
• Worker registry client start up error

AI-assisted analysis of apache/dolphinscheduler@02eac45a1b (2026-09-06). Data as JSON: /api/errors/9b19e91646867472. Report an issue: GitHub.