prestodb/presto · error · ClientException

Fully qualified name of localhost should not resolve to 'loc

Error message

Fully qualified name of localhost should not resolve to 'localhost'. System configuration error?

What it means

canonicalizeServiceHostName resolves the host to a fully qualified name via InetAddress canonical host names, and refuses 'localhost' as the result, throwing a ClientException. SPNEGO service principals must contain the real FQDN (HTTP/host.example.com@REALM); a localhost resolution means the machine's hostname/network is misconfigured and the resulting principal would not match the KDC.

Source

Thrown at presto-client/src/main/java/com/facebook/presto/client/SpnegoHandler.java:261

        if (useCanonicalHostname) {
            serviceHostName = canonicalizeServiceHostName(hostName);
        }
        return format("%s@%s", serviceName, serviceHostName.toLowerCase(Locale.US));
    }

    private static String canonicalizeServiceHostName(String hostName)
    {
        try {
            InetAddress address = InetAddress.getByName(hostName);
            String fullHostName;
            if ("localhost".equalsIgnoreCase(address.getHostName())) {
                fullHostName = InetAddress.getLocalHost().getCanonicalHostName();
            }
            else {
                fullHostName = address.getCanonicalHostName();
            }
            if (fullHostName.equalsIgnoreCase("localhost")) {
                throw new ClientException("Fully qualified name of localhost should not resolve to 'localhost'. System configuration error?");
            }
            return fullHostName;
        }
        catch (UnknownHostException e) {
            throw new ClientException("Failed to resolve host: " + hostName, e);
        }
    }

    private interface GssSupplier<T>
    {
        T get()
                throws GSSException;
    }

    private static <T> T doAs(Subject subject, GssSupplier<T> action)
            throws GSSException
    {
        try {

View on GitHub (pinned to 55bb57d202)

Solutions

1. Fix /etc/hosts so the machine's real hostname maps to its real IP, with 127.0.0.1 pointing only to 'localhost'.
2. Set a proper hostname (hostnamectl set-hostname host.example.com).
3. Fix reverse DNS (PTR record) with your DNS admin so the IP canonicalizes to the FQDN.
4. Verify with: hostname -f (must not print 'localhost').

Example fix

// before (in /etc/hosts)
127.0.0.1  myhost.example.com myhost localhost
// after
127.0.0.1  localhost
10.0.0.5   myhost.example.com myhost

String fqdn = InetAddress.getLocalHost().getCanonicalHostName();
if ("localhost".equalsIgnoreCase(fqdn)) {
    throw new IllegalStateException("Fix /etc/hosts or hostname: FQDN resolves to localhost");
}

try { ... } catch (ClientException e) { if (e.getMessage().contains("should not resolve to 'localhost'")) { /* fix hostname/DNS config */ } throw e; }

When it happens

Trigger: makeServicePrincipal -> canonicalizeServiceHostName when InetAddress.getLocalHost().getCanonicalHostName() (or the given address's) resolves to the string 'localhost'.

Common situations: /etc/hosts maps the machine's hostname to 127.0.0.1 or lists 'localhost' as canonical name; hostname set to 'localhost'; reverse DNS returning 'localhost'; container images with incomplete hostname setup.

Related errors

• Kerberos error for [%s]: %s
• Failed to resolve host:
• Authentication using Kerberos requires SSL to be enabled

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/5993ddecd8989776. Report an issue: GitHub.