Hi, we encounter this problem in our proc hadoop cluster:
Sometimes hive mysql metastore hang because deadlock, so result in all hive client hang infinitely. we check in this problem, found most mysql request hang on " SHOW FULL COLUMNS FROM `DELETEME1472008582981` FROM `hive` LIKE '%' " More interesting is mysql request span to multiple nodes will request table with same name, like below: | 5409551 | hive | 10.93.xx.54:23327 | hive | Query | 1476 | Waiting for table metadata lock | SHOW FULL COLUMNS FROM `DELETEME1472008582981` FROM `hive` LIKE '%' | | 5409557 | hive | 10.93.xx.20:3862 | hive | Query | 1473 | Waiting for table metadata lock | SHOW FULL COLUMNS FROM `DELETEME1472008582981` FROM `hive` LIKE '%' | | 5409567 | hive | 10.93.xx.51:48055 | hive | Query | 1469 | Waiting for table metadata lock | SHOW FULL COLUMNS FROM `DELETEME1472008582981` FROM `hive` LIKE '%' | | 5409576 | hive | 10.93.xx.32:18886 | hive | Sleep | 1464 | | NULL | | 5409577 | hive | 10.93.xx.32:18887 | hive | Query | 1463 | Waiting for table metadata lock | SHOW FULL COLUMNS FROM `DELETEME1472008582981` FROM `hive` LIKE '%' | | 5409587 | hive | 10.93.25.32:19582 | hive | Query | 1457 | Waiting for table metadata lock | SHOW FULL COLUMNS FROM `DELETEME1472008582981` FROM `hive` LIKE '%' obviously it is not identical with the datanucleus code in : RDBMSStoreManager.java <https://github.com/datanucleus/datanucleus-rdbms/blob/master/src/main/java/org/datanucleus/store/rdbms/RDBMSStoreManager.java>, which one hive session will create probeTable with current milliseconds("DELETEME+"). List above shows that five hive session among multiple node however request for ProbeTable with same name! And we check our configuration in hive-site.xml, autoCreateSchema(false) and fixedDataStore(true) has been set for long time. Code shows when this two properties is set, no "DELETEMExxx" table will be created and queried. so we want to figure out why our hive client will request for such "DELETEMExxx" table, so result in deadlock in mysql metastore database. Any suggestion will be welcome. Thanks! env: hive version: 1.2.1 metastore database: MySQL Local/Embedded Metastore Server Hive user: 100+ Best wishes! -- Wang Haihua