apache/seatunnel · warning

Failed to get clickhouse server config: {}

Error message

Failed to get clickhouse server config: {}

What it means

ClickhouseSinkWriter checks whether the ClickHouse server has the experimental lightweight delete feature enabled by querying system tables (SELECT value FROM system.<config>). On SQLException it logs this warning and returns false, so the writer proceeds assuming lightweight delete is disabled.

Source

Thrown at seatunnel-connectors-v2/connector-clickhouse/src/main/java/org/apache/seatunnel/connectors/seatunnel/clickhouse/sink/client/ClickhouseSinkWriter.java:230

    private boolean clickhouseServerEnableExperimentalLightweightDelete(
            ClickHouseConnectionImpl clickhouseConnection) {
        if (!option.isAllowExperimentalLightweightDelete()) {
            return false;
        }
        String configKey = "allow_experimental_lightweight_delete";
        try (Statement stmt = clickhouseConnection.createStatement();
                ResultSet resultSet =
                        stmt.executeQuery("SHOW SETTINGS ILIKE '%" + configKey + "%'")) {
            while (resultSet.next()) {
                String name = resultSet.getString("name");
                if (name.equalsIgnoreCase(configKey)) {
                    return resultSet.getBoolean("value");
                }
            }
            return false;
        } catch (SQLException e) {
            log.warn("Failed to get clickhouse server config: {}", configKey, e);
            return false;
        }
    }
}

View on GitHub (pinned to cf67b549a7)

Solutions

1. Grant the configured ClickHouse user read access to system tables, or check the exact SQLException in the log cause.
2. Upgrade ClickHouse if the required config table/feature is absent but lightweight delete is desired.
3. Accept the fallback (feature treated as disabled) if your sink config does not rely on lightweight delete.

// pre-check feature flag before writing
SELECT value FROM system.system_settings WHERE name = 'enable_experimental_lightweight_delete';

try {
    boolean enabled = writer.checkLightweightDelete();
} catch (SQLException e) {
    // connector already falls back to false; log and continue
}

When it happens

Trigger: clickhouseServerEnableExperimentalLightweightDelete executes its config query and the JDBC statement fails — table missing on old ClickHouse versions, connection drop, or permission denied on system tables.

Common situations: ClickHouse versions without the checked system table; limited DB user lacking access to system.* tables; transient network issues between SeaTunnel and ClickHouse.

Understand the failure class

Background: "query failed", "%w: SQL error" — wrapped database query errors in Go libraries explained — this error's family across 3 libraries.

Related errors

• Failed to execute query: %s
• Failed to analyze SQL complexity using EXPLAIN, fallback to
• Failed to split chunks for table " + tableId
• Error to discover tables:
• Error to check tables:

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/2e480196cb7de3bb. Report an issue: GitHub.