apache/cassandra · error

Seed provider couldn't lookup host

Error message

Seed provider couldn't lookup host {}

What it means

SimpleSeedProvider.getSeeds failed DNS resolution of a seed host from cassandra.yaml (UnknownHostException). Not fatal: the host is skipped and logged so startup can continue with remaining seeds; DatabaseDescriptor later complains if no seeds resolve.

Solutions

1. Verify the seed hostname is correct and resolvable via DNS on this node (nslookup/dig).
2. Fix cassandra.yaml seed_provider entries or /etc/resolv.conf / /etc/hosts.
3. Use IP addresses instead of hostnames if DNS is unreliable.

When it happens

Trigger: Thrown at src/java/org/apache/cassandra/locator/SimpleSeedProvider.java:106 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/739eb435351a5c14. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/locator/SimpleSeedProvider.java:106

                {
                    if (resolveMultipleIps)
                    {
                        List<InetAddressAndPort> resolvedSeeds = InetAddressAndPort.getAllByName(host.trim());
                        seeds.addAll(resolvedSeeds);
                        logger.debug("{} resolves to {}", host, resolvedSeeds);
                    }
                    else
                    {
                        InetAddressAndPort addressAndPort = InetAddressAndPort.getByName(host.trim());
                        seeds.add(addressAndPort);
                        logger.debug("Only resolving one IP per DNS record - {} resolves to {}", host, addressAndPort);
                    }
                }
            }
            catch (UnknownHostException ex)
            {
                // not fatal... DD will bark if there end up being zero seeds.
                logger.warn("Seed provider couldn't lookup host {}", host);
            }
        }

        if (seeds.size() > SEED_COUNT_WARN_THRESHOLD)
            logger.warn("Seed provider returned more than {} seeds. " +
                        "A large seed list may impact effectiveness of the third gossip round.",
                        SEED_COUNT_WARN_THRESHOLD);

        return Collections.unmodifiableList(seeds);
    }
}

View on GitHub (pinned to 88fd0f6a0e)