apache/druid · error · RE

%s: Malformed url for DruidNode [%s] and baseUrl [%s]

Error message

%s: Malformed url for DruidNode [%s] and baseUrl [%s]

What it means

getListenerURL builds the catalog sync listener URL from a DruidNode's host/port and a baseUrl. If java.net.URL considers the constructed string malformed (bad host characters, missing scheme after concat, illegal port), it logs and rethrows as a ResourceException (RE) wrapping the MalformedURLException.

Source

Thrown at extensions-core/druid-catalog/src/main/java/org/apache/druid/catalog/sync/RestUpdateSender.java:190

                      cacheNotificationsTimeoutMs,
                      TimeUnit.MILLISECONDS
                  );
  }

  private URL getListenerURL(DruidNode druidNode, String baseUrl)
  {
    try {
      return new URL(
          druidNode.getServiceScheme(),
          druidNode.getHost(),
          druidNode.getPortToUse(),
          baseUrl
      );
    }
    catch (MalformedURLException mue) {
      String msg = StringUtils.format(callerName + ": Malformed url for DruidNode [%s] and baseUrl [%s]", druidNode, baseUrl);
      LOG.error(msg);
      throw new RE(mue, msg);
    }
  }
}

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Fix druid.host to a valid URL hostname (RFC 1123: no underscores, use hyphens) and restart.
2. Ensure baseUrl includes the scheme, e.g. 'http://' or 'https://'.
3. If using IPv6, set druid.host to the bracketed form or a resolvable hostname.
4. Log/inspect the generated URL string (druidNode + baseUrl) to spot the malformed part, then correct the config value.

Example fix

// before
druid.host=my_pod_name   // underscore -> Malformed URL

// after
druid.host=my-pod-name.my-namespace.svc.cluster.local

String host = druidNode.getHost();
if (host.contains("_") || !baseUrl.matches("^https?://.*")) {
  throw new IllegalArgumentException("Invalid druid.host or baseUrl missing scheme: " + host + ", " + baseUrl);
}

try {
  URL url = getListenerURL(druidNode, callerName, baseUrl);
} catch (RE e) {
  LOG.error("Bad catalog listener URL config: host=%s baseUrl=%s", druidNode.getHost(), baseUrl);
}

When it happens

Trigger: accept() → getListenerURL() with a druidNode whose host contains invalid URL characters (e.g. underscores, IPv6 literal without brackets) or a baseUrl missing the http(s):// scheme, so the concatenation 'scheme://host:port/baseUrl' fails URL parsing.

Common situations: Kubernetes pod names with underscores used as druid.host; baseUrl configured without protocol; misconfigured druid.host containing scheme already (double scheme); special characters from templated config values.

Understand the failure class

Background: "Invalid URL" errors: why new URL(), URI.parse, and reqwest::Url reject your string — missing scheme, whitespace, and bad path format — this error's family across 39 libraries.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Bad URL: %s
• Failed to construct server URL.
• Failed to start lookup [%s]:[%s]
• The gRPC query server requires either a Basic or Anonymous a
• Metric [%s] not whitelisted.

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/2b710c318a46898d. Report an issue: GitHub.