2/1/2024 0 Comments Wordpress mysql deadlock![]() The easiest way to ensure that subsequent processes do not start processing the critical section code is to use a shared flag between processes. But how to ensure that other processes wait for the colleague who first entered the section? Mutex The critical section is what we call a particular part of the code that can only be executed simultaneously by one process. Subsequent processes should wait until the previous process finishes processing such code. The solution to the problem is obvious: you need to protect the part of the code that cannot run parallelly. The crux of the problem we encounter lies in that more than one process can execute the same code in parallel. The success of such an operation depends on luck it is a bug that is very difficult to reproduce and fix. When the result of an operation depends on processes execution order, it is called race conditions. Since we are using the API, we cannot convert both activities into one query.Įither of these two situations makes it impossible to solve the problem simply by converting to atomic operation. If there may appear a situation where two clients send an API request and get stock value first and then save the modified one, one of the processes may overwrite the data with an incorrect value. Suppose that, as part of handling a customer request, we want to take the stock value of a certain product, reduce it by one and save it. WooCommerce also allows you to change the inventory using the API. Regardless of how sending the SMS is done, we cannot easily combine it with modifying the database's inventory. Thankfully it was just an SMS, not a transfer of half a million dollars. The administrator will get two SMSs instead of one, even though the inventory reduction is atomic. The first process will not update the store until the second process has read its state. If two processes take the stock simultaneously, both can receive the number 5 and send an SMS. If we have exactly five products in stock, maybe we would like to send the warehouse admin an SMS informing them that the products are running out. Imagine that you want to make an operation in a store that is dependent on stock. The atomic operation is not always enough If you don't know what these operations are like, read it first. We look for both the 2 lock struct(s) and the ACTIVE 21 sec messages.This entry is a continuation of atomic operations. MySQL thread id 217, OS thread handle 0x2aef097700, query id 1177 1.3.5.7 mpsp cleaning up In our TRANSACTIONS section we also see the following: -TRANSACTION 644793773, ACTIVE 21 secĢ lock struct(s), heap size 360, 1 row lock(s) This worked on AWS MySQL RDS as well as local MySQL. To kill it you need to execute by using the "thread id #" specified - in this case: kill 12505095 MySQL thread id 12505095, query id 909492789 129.54įor us it was the # lock struct(s) that indicated a stuck lock. In your output the relevant problem seems to be: 3 lock struct(s), heap size 1248, 2 row lock(s) The relevant section is in the TRANSACTIONS section. This spits out a crap-ton of information. We found the locks by combing trough the output from: show engine innodb status We were seeing Java hibernate issues causing stuck locks. Using 'show engine innodb status' I see that wordpress has two deadlocks. RECORD LOCKS space id 4951009 page no 4 n bits 384 index `option_name` of table `wordpress_work`.`wp_options` trx id 9FBA0995 lock_mode X waiting *** (2) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 4951009 page no 4 n bits 384 index `option_name` of table `wordpress_work`.`wp_options` trx id 9FBA0995 lock_mode X locks rec but not gap TRANSACTION 9FBA0995, ACTIVE 0 sec, process no 14207, OS thread id 1230031168 starting index readģ lock struct(s), heap size 1248, 2 row lock(s) RECORD LOCKS space id 4951009 page no 4 n bits 384 index `option_name` of table `wordpress_work`.`wp_options` trx id 9FBA099E lock_mode X waiting *** (1) WAITING FOR THIS LOCK TO BE GRANTED: MySQL thread id 12505112, query id 909492800 129.54 wordpress_user updatingĭELETE FROM wp_options WHERE option_name = ''_site_transient_timeout_theme_roots'' LOCK WAIT 2 lock struct(s), heap size 376, 1 row lock(s) TRANSACTION 9FBA099E, ACTIVE 0 sec, process no 14207, OS thread id 1228433728 starting index read I can see thread ids, query ids, etc but nothing that I can use to stop either job.ĮDIT: Here's the (relevant?) portion of the status:. I'd like to clear these up but I don't see an active process for either of these cmds (IE something to 'kill' and hopefully force a rollback).
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