{"record":{"id":"7c689b40dcb9d9a8","repo":"alibaba/canal","slug":"command-show-variables-like-server-id-has-an-e-7c689b","errorCode":null,"errorMessage":"command : show variables like 'server_id' has an error!","messagePattern":"command : show variables like 'server_id' has an error!","errorType":"exception","errorClass":"CanalParseException","httpStatus":null,"severity":"error","filePath":"parse/src/main/java/com/alibaba/otter/canal/parse/inbound/mysql/MysqlEventParser.java","lineNumber":659,"sourceCode":"            }\n        }\n        // 找不到\n        return null;\n    }\n\n    /**\n     * 查询当前db的serverId信息\n     */\n    private Long findServerId(MysqlConnection mysqlConnection) {\n        try {\n            ResultSetPacket packet = mysqlConnection.query(\"show variables like 'server_id'\");\n            List<String> fields = packet.getFieldValues();\n            if (CollectionUtils.isEmpty(fields)) {\n                throw new CanalParseException(\"command : show variables like 'server_id' has an error! pls check. you need (at least one of) the SUPER,REPLICATION CLIENT privilege(s) for this operation\");\n            }\n            return Long.valueOf(fields.get(1));\n        } catch (IOException e) {\n            throw new CanalParseException(\"command : show variables like 'server_id' has an error!\", e);\n        }\n    }\n\n    /**\n     * 查询当前的binlog位置\n     */\n    private EntryPosition findEndPosition(MysqlConnection mysqlConnection) {\n        String showSql = \"show master status\";\n        try {\n            if (mysqlConnection.atLeastMySQL84()) {\n                // 8.4新语法\n                showSql = \"show binary log status\";\n            } else if (multiStreamEnable) {\n                // 兼容polardb-x的多流binlog\n                showSql = \"show master status with \" + destination;\n            }\n            ResultSetPacket packet = mysqlConnection.query(showSql);\n            List<String> fields = packet.getFieldValues();","sourceCodeStart":641,"sourceCodeEnd":677,"githubUrl":"https://github.com/alibaba/canal/blob/87be50e87686a3e8af08c368d0e1ffd1f59eb04a/parse/src/main/java/com/alibaba/otter/canal/parse/inbound/mysql/MysqlEventParser.java#L641-L677","documentation":"findServerId()'s catch (IOException) wraps any I/O failure of the `show variables like 'server_id'` query in CanalParseException. Unlike error 396 (empty result = privilege), this fires when the query itself fails at the transport/protocol level — the connection broke, timed out, or the server returned a protocol error.","triggerScenarios":"The query throws IOException — network drop, connection closed by server, socket timeout, or an authentication/protocol error mid-query.","commonSituations":"Transient network failure to the master; connection idle-timed out (wait_timeout); server restarted mid-session; firewall killed the connection; SSL handshake failure surfacing as IO error.","solutions":["Check network connectivity and latency between canal and the MySQL master.","Increase connection/socket timeout (defaultConnectionTimeoutInSeconds) if the query is timing out.","Ensure the connection is alive before the query; canal's reconnect logic should retry — verify retry/HA config.","Inspect the wrapped IOException cause for the precise failure (SocketTimeoutException, Connection reset, etc.)."],"exampleFix":null,"handlingStrategy":"retry","validationCode":"// Verify connectivity before the metadata query\nif (!connection.isConnected()) {\n    connection.reconnect();\n}","typeGuard":null,"tryCatchPattern":"try {\n    return findServerId(mysqlConnection);\n} catch (CanalParseException e) {\n    if (e.getCause() instanceof IOException) {\n        logger.warn(\"Transient IO error reading server_id, will reconnect and retry once\", e);\n        mysqlConnection.reconnect();\n        return findServerId(mysqlConnection); // single retry\n    }\n    throw e;\n}","preventionTips":["Increase defaultConnectionTimeoutInSeconds to absorb slow networks.","Ensure canal reconnect/HA retry is enabled.","Inspect the IOException cause to distinguish transient vs permanent failures."],"tags":["mysql","network","io","server-id","canal-parse"],"backgroundTag":null,"analyzedSha":"87be50e87686a3e8af08c368d0e1ffd1f59eb04a","analyzedAt":"2026-08-14T04:30:11.918Z","schemaVersion":2},"datasetVersion":"2026-08-14T05:17:29.042Z"}