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The recommended default sources are of little help: INFORMATION_SCHEMA.INNODB_TRX shows the transaction, but nothing above can help me find it. Only this 1 table is locked (in this small dummy example) and this trx_mysql_thread_id is 4093. mysql> select * from INFORMATION_SCHEMA.INNODB_TRX G ******************** * ****** First line ************************** trx_id: 280907 trx_state: WORK trx_started: 2018-11-30 00: 35 :06 trx_requested_lock_id: NULL trx_wait_started: NULL trx_weight: 3 trx_mysql_thread_id: 4093 trx_query: NULL trx_operation_state: NULL trx_tables_in_use: 0 trx_tables_locked: 1 trx_lock_structs: 2 trx_lock_memory_bytes: 1136 trx_rows_locked: 1 trx_rows_modified: 1 trx_concurrency_tickets: 0 trx_isolation_level: REPEATABLE READ trx_unique_checks: 1 trx_foreign_key_checks : 1 trx_last_foreign_key_error: NULL trx_adaptive_hash_latched: 0 trx_adaptive_hash_timeout: 0 trx_is_read_only: 0 trx_autocommit_non_locking: 0 1 string per set (0.00s) for all locks. Additionally, INNODB_LOCKS is deprecated anyway. SHOW ENGINE INNODB STATUS is useless: cfgNodes is not listed at all. SHOW FULL PROCESSLIST is empty because the culprit is not currently executing the request. But do you remember the old trx_mysql_thread_id now? We can use this to show the requirements of this transaction: -> AND T.PROCESSLIST_ID = 4093 -> ORDER BY ESH.EVENT_ID LIMIT 10; + ----------------------------------------------- + | SQL_TEXT | + ----------------------------------------------- + | Select the restriction @@ version_comment 1 | | Start transaction | | update set cfgNodes name = foobar where ID = 29 | + ------------------------------------------------- ------------ ------------- + 3 lines in a sentence (0.00 sec) Voila - now we can see the history of the last 10 requests for each of the remaining transactions, which will allow us to find the culprit. (Respectfully ignore specific DB responses) If you are using a formal CRUD schema where all DB traffic is routed through a singleton class, you may still encounter thread blocking. This is often the result of an oversight between you, the university, and the Hibernate team. Therefore, the fastest way is to check the code for errors, paying close attention to the basic principles of hibernation. Typically, the CRUD interface has the public methods Create, Read, Update, and Delete which use public methods. This is for DRY Best Practice. However, these methods work perfectly well in most cases, but not always. So how do you check and solve thread blocking? Make sure session.save (myObj) actions check the uniqueness of PK first. All uniqueResult () queries actually return 1 result, And; (Important!) Concentrate on test cases which: Introducing duplicate PCsThe sources suggested by default are not very helpful: INFORMATION_SCHEMA.INNODB_TRX shows the transaction but does little to help you find it. Only this 1 table is locked (in this little fake example) and the trx_mysql_thread_id is 4093. mysql> select * from INFORMATION_SCHEMA.INNODB_TRX G ********************* * * * ***** Line 1 ***************************** trx_id: 280907 trx_state: RUNNING trx_started: 2018-11 -30 00:35 :06 trx_requested_lock_id: NULL trx_wait_started: NULL trx_weight: 3 trx_mysql_thread_id: 4093 trx_query: NULL trx_operation_state: NULL trx_tables_in_use: 0 trx_tables_locked: 1 trx_lock_structs: 2 trx_lock_memory_bytes: 1136 trx_rows_locked: 1 trx_rows_modified: 1 trx_concurrency_tickets: 0 trx_isolation_level: REPEATABLE READ trx_unique_checks: 1 trx_foreign_key_checks: 1 trx_last_foreign_key_error: NULL trx_adaptive_hash_latched: 0 trx_adaptive_hash_timeout: 0 trx_is_read_only: 0 trx_autocommit_non_locking: 0 1 line in transaction set (0.00 sec) NO because the empty documentation does not currently exist. for all locks. Also, INNODB_LOCKS is deprecated anyway. SHOW ENGINE INNODB STATUS is useless: cfgNodes is not listed at all. SHOW FULL PROCESSLIST is empty because the culprit is not currently running the query. But now remember the trx_mysql_thread_id from earlier? We can use this to show the queries executed in this transaction: mysql> SELECT SQL_TEXT -> FROM performance_schema.events_statements_history ESH, -> performance_schema.threads T -> WHERE ESH.THREAD_ID = T.THREAD_ID -> AND ESH.SQL_NULL IS NOT - > AND T.PROCESSLIST_ID = 4093 -> ORDER BY ESH.EVENT_ID RESTRICTION 10; + ------------------------------------------------ + | SQL_TEXT | + ------------------------------------------------ + | select @@ version_comment limit 1 | | Start transaction | | update cfgNodes set name = foobar where id = 29 | +------------------------------------------------- ------------ - -------- + 3 rows in a sentence (0.00s) Voila, were now seeing the history of the last 10 queries for each remaining transaction, giving us what it takes allows to find the culprit. (Respectfully ignore database-specific answers) With a formal CRUD scheme, where all database traffic is routed through a singleton class, you can still encounter thread deadlock. Often this is due to misunderstandings between you, the university and the Hibernate team. Therefore, the fastest way is to check the code for errors - paying special attention to the basic principles of hibernation. Typically a CRUD interface has public methods Create, Read, Update and Delete that share private methods. This is done to ensure best DRY practice. However, in this way, these methods work fine most of the time, but not always. So how do you test and fix a threadlock issue? Make sure: session.save(myObj) operations check PK uniqueness first All uniqueResult() queries actually return 1 result, And; (Important!) Concentration of test cases that: Introduce duplicate PKs

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