apache/seatunnel · error · ClickhouseConnectorException

Failed to connect to host: " + host + " by user: " + user +

Error message

Failed to connect to host: " + host + " by user: " + user + " on port 22

What it means

RsyncFileTransfer.init wraps IOException/GeneralSecurityException from establishing or authenticating the SSH session in an SSH_OPERATION_FAILED exception whose message is "Failed to connect to host: <host> by user: <user> on port 22", with the original exception as cause.

Source

Thrown at seatunnel-connectors-v2/connector-clickhouse/src/main/java/org/apache/seatunnel/connectors/seatunnel/clickhouse/sink/file/RsyncFileTransfer.java:86

            sshClient.start();
            clientSession = sshClient.connect(user, host, SSH_PORT).verify().getSession();
            if (password != null) {
                clientSession.addPasswordIdentity(password);
            }
            if (keyPath != null) {
                FileKeyPairProvider fileKeyPairProvider =
                        new FileKeyPairProvider(Paths.get(keyPath));
                KeyPair fileKeyPair =
                        fileKeyPairProvider.loadKey(clientSession, KeyPairProvider.SSH_RSA);
                clientSession.addPublicKeyIdentity(fileKeyPair);
            }
            if (!clientSession.auth().verify().isSuccess()) {
                throw new ClickhouseConnectorException(
                        ClickhouseConnectorErrorCode.SSH_OPERATION_FAILED,
                        "ssh host " + host + "authentication failed");
            }
        } catch (IOException | GeneralSecurityException e) {
            throw new ClickhouseConnectorException(
                    ClickhouseConnectorErrorCode.SSH_OPERATION_FAILED,
                    "Failed to connect to host: " + host + " by user: " + user + " on port 22",
                    e);
        }
    }

    @Override
    public void transferAndChown(String sourcePath, String targetPath) {
        try {
            String sshParameter =
                    password != null
                            ? String.format(
                                    "'sshpass -p %s ssh -o StrictHostKeyChecking=no -p %s'",
                                    password, SSH_PORT)
                            : keyPath != null
                                    ? String.format(
                                            "'ssh -i %s -o StrictHostKeyChecking=no -p %s'",
                                            keyPath, SSH_PORT)

View on GitHub (pinned to cf67b549a7)

Solutions

1. Check the chained cause for the exact network/IO error
2. Verify connectivity: `ssh <user>@<host>` or `nc -vz <host> 22` from the SeaTunnel worker machine
3. Confirm sshd is running on the ClickHouse node and the firewall allows port 22
4. Fix the hostname/IP and user in the sink configuration

try {
    transfer.init();
} catch (ClickhouseConnectorException e) {
    if (e.getMessage() != null && e.getMessage().contains("Failed to connect to host")) {
        // check network/sshd/firewall before retrying with backoff
    }
}

When it happens

Trigger: init when the SSH connection to port 22 fails — host unreachable, wrong host/port, firewall blocking, SSH daemon down, DNS failure, or a GeneralSecurityException during crypto/key handling.

Common situations: ClickHouse node firewall blocks port 22 from the worker; sshd not running on the target; hostname typo or stale DNS; network partition between SeaTunnel worker and ClickHouse node.

Understand the failure class

Background: ECONNREFUSED and "connection refused" / "could not connect to server" errors: what they mean and how to fix them — this error's family across 44 libraries.

Related errors

• Failed to close ssh session
• Failed to close ssh client
• Failed to connect to host: " + host + " by user: " + user +
• Failed to close ssh session
• Failed to close ssh client

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/8921454d20ea50d1. Report an issue: GitHub.