apache/flink · error · IllegalArgumentException

The given host:port (' ') is invalid

Error message

The given host:port ('{}') is invalid

What it means

This IllegalArgumentException wraps a java.net.MalformedURLException raised while NetUtils.validateHostPortString turns the input into a URL. It means the string is not parseable as a URL at all — malformed syntax rather than merely a missing host or port. The original MalformedURLException is attached as the cause for details.

Solutions

1. Read the cause (MalformedURLException) to see where parsing failed.
2. For IPv6, bracket the address: 'http://[fe80::1]:8081' or '[fe80::1]:8081'.
3. Trim whitespace and remove duplicate schemes or stray path/query suffixes from the value.
4. If the field expects bare host:port, do not also include a scheme that conflicts with the auto-prepended one.

Example fix

// before
String address = "fe80::1:8081"; // ambiguous IPv6

// after
String address = "[fe80::1]:8081";

static boolean isParsableHostPort(String s) {
    try { new java.net.URL(s.startsWith("http") ? s : "http://" + s); return true; }
    catch (java.net.MalformedURLException e) { return false; }
}

try { NetUtils-validating call } catch (IllegalArgumentException e) { Throwable cause = e.getCause(); if (cause instanceof MalformedURLException) { /* report malformed value, keep cause */ } }

When it happens

Trigger: Inputs like 'host:8081:extra', an unbracketed IPv6 literal such as 'fe80::1:8081', 'http://host:NotAPort', or strings containing illegal URL characters (spaces, stray slashes) passed to host:port validation.

Common situations: IPv6 addresses used without square brackets; copy-pasted endpoints with trailing paths or whitespace; interpolating a full URL into a field that already gets the 'http://' prefix, producing 'http://http://host:port'.

Related errors

• The configured hostname is not valid
• The given host:port (' ') doesn't contain a valid host
• The given host:port (' ') doesn't contain a valid port
• Address cannot be resolved
• address is null

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/08cec05b7e97e282. Report an issue: GitHub.

Appendix: source

Thrown at flink-core/src/main/java/org/apache/flink/util/NetUtils.java:125

            throw new IllegalArgumentException("hostPort should not be null or empty");
        }
        try {
            URL u =
                    (hostPort.toLowerCase().startsWith("http://")
                                    || hostPort.toLowerCase().startsWith("https://"))
                            ? new URL(hostPort)
                            : new URL("http://" + hostPort);
            if (u.getHost() == null) {
                throw new IllegalArgumentException(
                        "The given host:port ('" + hostPort + "') doesn't contain a valid host");
            }
            if (u.getPort() == -1) {
                throw new IllegalArgumentException(
                        "The given host:port ('" + hostPort + "') doesn't contain a valid port");
            }
            return u;
        } catch (MalformedURLException e) {
            throw new IllegalArgumentException(
                    "The given host:port ('" + hostPort + "') is invalid", e);
        }
    }

    /**
     * Converts an InetSocketAddress to a URL. This method assigns the "http://" schema to the URL
     * by default.
     *
     * @param socketAddress the InetSocketAddress to be converted
     * @return a URL object representing the provided socket address with "http://" schema
     */
    public static URL socketToUrl(InetSocketAddress socketAddress) {
        String hostString = socketAddress.getHostString();
        // If the hostString is an IPv6 address, it needs to be enclosed in square brackets
        // at the beginning and end.
        if (socketAddress.getAddress() != null
                && socketAddress.getAddress() instanceof Inet6Address
                && hostString.equals(socketAddress.getAddress().getHostAddress())) {

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