apache/beam · error · IllegalArgumentException

Could not parse pubsub root url "%s"

Error message

Could not parse pubsub root url "%s"

What it means

PubsubOptions.targetForRootUrl converts a custom Pub/Sub root URL into a host[:port] target for the gRPC channel. If the URL string cannot be parsed by java.net.URL (MalformedURLException), it throws IllegalArgumentException with this message and the cause.

Source

Thrown at sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsub/PubsubOptions.java:48

/** Properties that can be set when using Google Cloud Pub/Sub with the Apache Beam SDK. */
@Description(
    "Options that are used to configure Google Cloud Pub/Sub. See "
        + "https://cloud.google.com/pubsub/docs/overview for details on Cloud Pub/Sub.")
public interface PubsubOptions
    extends ApplicationNameOptions, GcpOptions, PipelineOptions, StreamingOptions {

  /**
   * Internal only utility for converting {@link #getPubsubRootUrl()} (e.g. {@code https://<host>})
   * to an endpoint target, usable by GCP client libraries (e.g. {@code <host>:443})
   */
  @Internal
  static String targetForRootUrl(String urlString) {
    URL url;
    try {
      url = new URL(urlString);
    } catch (MalformedURLException e) {
      throw new IllegalArgumentException(
          String.format("Could not parse pubsub root url \"%s\"", urlString), e);
    }

    int port = url.getPort();

    if (port < 0) {
      switch (url.getProtocol()) {
        case "https":
          port = 443;
          break;
        case "http":
          port = 80;
          break;
        default:
          throw new IllegalArgumentException(
              String.format(
                  "Could not determine port for pubsub root url \"%s\". You must either specify the port or use the protocol \"https\" or \"http\"",
                  urlString));

View on GitHub (pinned to 12126d8942)

Solutions

  1. Fix the pubsubRootUrl value to be a well-formed absolute URL, e.g. 'https://pubsub.googleapis.com' or 'http://localhost:8085'.
  2. Validate the URL with new URL(...) or a regex before setting the option.
  3. Check the config file/flag for stray characters, spaces, or unescaped quotes.

Example fix

// before
--pubsubRootUrl=localhost:8085   // may be rejected depending on parse
// after
--pubsubRootUrl=http://localhost:8085
Defensive patterns

Strategy: validation

Validate before calling

try { new java.net.URL(urlString); } catch (java.net.MalformedURLException e) {
  throw new IllegalArgumentException("pubsubRootUrl must be an absolute URL like http://localhost:8085", e);
}

Try / catch

try {
  options.setPubsubRootUrl(urlString);
} catch (IllegalArgumentException e) {
  log.error("Bad pubsubRootUrl: {}", urlString, e);
}

Prevention

When it happens

Trigger: Setting the pubsubRootUrl option/property to a malformed string, e.g. missing scheme ('localhost:8085' is fine, but 'localhost//' or '::bad::' is not) or containing invalid characters.

Common situations: Pointing at a local emulator or mock server and typos in the URL, quoting mistakes in config files, or missing the scheme entirely in ways java.net.URL rejects.

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.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/3db46a7a158f1248. Report an issue: GitHub.