MySQL 8.0 : Error Logging

By

MySQL 8.0 : Error Logging

MySQL 8.0 : Error Logging

Here I would like to explain, How MySQL 8.0 server can be configured to log diagnosis messages inside the error log file. 

Generally, the error log contains:
  • A record for mysqld service startup and shutdown.
  • Diagnostic messages such as errors, warnings, and notes during mysqld server startup, running or shut down. 
  • A stack trace if mysqld exits abnormally. 
  • mysqld_safe writes once it finds mysqld exists abnormally and mysqld_safe invoke/start mysqld. 

Error Log Component Configuration

MySQL 8.0 uses the MySQL error log component architecture that performs log event filtering and writing. These error log components can be configured using the system variable to achieve the desired logging results inside the error log file.

We have mainly two types of error log components: filter & sink.

  • Error Log Filter Components --->  Filter components, mainly process log events, to add, delete or modify event fields or to delete events entirely. 
  • Error Log Sink Components ---> Sink components, mainly log events into log messages in a particular format and then write these messages to its associated output such as into file or the system log. 
We have below error log components based on their category of filter & sink(writer). 
  • Error Log Sink Components
    • log_sink_internal
      • Purpose: Traditional error log message output format. Write inside file_name defined under log_error parameter. 
      • URN: Built-in component/default component
    • log_sink_json
      • Purpose: JSON-format error logging. Write inside the file named as file_name.NN.json
      • URN: file://component_log_sink_json
    • log_sink_syseventlog
      • Purpose: Error logging to the system log. Write to the system log file, regardless of the defined log_error parameter value.
      • URN: file://component_log_sink_syseventlog
    • log_sink_test
      • Purpose: Internal use in writing test cases. Not intended for production use.
      • URN: file://component_log_sink_test
These filter/sink components can be configured using the log_error_services system variable. 

The server executes the filter/sink components in the defined/named order inside the log_error_services parameter. So, we need to make sure the rightmost component should be the sink(writer) component. If we mistakenly place filter component as a rightmost component, then any changes on its event will have no effect on output. 

Below is the default value of log_error_services. 
mysql [localhost:8015] {msandbox} ((none)) > select @@global.log_error_services;
+----------------------------------------+
| @@global.log_error_services            |
+----------------------------------------+
| log_filter_internal; log_sink_internal |
+----------------------------------------+
1 row in set (0.00 sec) 

If we need to change log_error_services parameter value with new filter/sink component then we first need to load/enable/install that component using the "INSTALL COMPONENT" command(unless the component is a built-in component or already loaded). 

Here I will load some non-default filter/sink component using the "INSTALL COMPONENT" command with their respective URN. 
mysql [localhost:8015] {msandbox} ((none)) > INSTALL COMPONENT "file://component_log_filter_dragnet";
Query OK, 0 rows affected (0.20 sec)


mysql [localhost:8015] {msandbox} ((none)) > INSTALL COMPONENT "file://component_log_sink_json";
Query OK, 0 rows affected (0.01 sec)


mysql [localhost:8015] {msandbox} ((none)) > INSTALL COMPONENT "file://component_log_sink_syseventlog";
Query OK, 0 rows affected (0.01 sec)


We can check the list of manually loaded components from table mysql.component. 

mysql [localhost:8015] {msandbox} ((none)) > select * from mysql.component;
+--------------+--------------------+---------------------------------------+
| component_id | component_group_id | component_urn                         |
+--------------+--------------------+---------------------------------------+
|            1 |                  1 | file://component_log_filter_dragnet   |
|            2 |                  2 | file://component_log_sink_json        |
|            3 |                  3 | file://component_log_sink_syseventlog |
+--------------+--------------------+---------------------------------------+
3 rows in set (0.00 sec)


For example, now suppose we need to use system log writer(log_sink_syseventlog) instead of the default writer (log_sink_internal) then we can just set it dynamically to log_error_services parameters.

Note: above we have already installed the component log_sink_syseventlog.
mysql [localhost:8015] {msandbox} ((none)) > set global log_error_services="log_filter_internal; log_sink_syseventlog";
Query OK, 0 rows affected (0.00 sec)


mysql [localhost:8015] {msandbox} ((none)) > select @@global.log_error_services;
+-------------------------------------------+
| @@global.log_error_services               |
+-------------------------------------------+
| log_filter_internal; log_sink_syseventlog |
+-------------------------------------------+
1 row in set (0.00 sec)


If we need to UNINSTALL COMPONENT then we need to first make sure that COMPONENT is not being used inside the log_error_services parameter. If it is defined then first remove that component from log_error_services and then we can UNINSTALL that component.

Like example:
mysql [localhost:8015] {msandbox} ((none)) > select @@global.log_error_services;
+-------------------------------------------+
| @@global.log_error_services               |
+-------------------------------------------+
| log_filter_internal; log_sink_syseventlog |
+-------------------------------------------+
1 row in set (0.00 sec)

mysql [localhost:8015] {msandbox} ((none)) > UNINSTALL COMPONENT "file://component_log_sink_syseventlog";
ERROR 3540 (HY000): Unregistration of service implementation 'log_service.log_sink_syseventlog' provided by component 'mysql:log_sink_syseventlog' failed during unloading of the component.

mysql [localhost:8015] {msandbox} ((none)) > set global log_error_services="log_filter_internal; log_sink_internal";
Query OK, 0 rows affected (0.00 sec)

mysql [localhost:8015] {msandbox} ((none)) > UNINSTALL COMPONENT "file://component_log_sink_syseventlog";
Query OK, 0 rows affected (0.01 sec)

mysql [localhost:8015] {msandbox} ((none)) > select @@global.log_error_services;
+----------------------------------------+
| @@global.log_error_services            |
+----------------------------------------+
| log_filter_internal; log_sink_internal |
+----------------------------------------+
1 row in set (0.00 sec)

mysql [localhost:8015] {msandbox} ((none)) > select * from mysql.component;
+--------------+--------------------+-------------------------------------+
| component_id | component_group_id | component_urn                       |
+--------------+--------------------+-------------------------------------+
|            1 |                  1 | file://component_log_filter_dragnet |
|            2 |                  2 | file://component_log_sink_json      |
+--------------+--------------------+-------------------------------------+
2 rows in set (0.00 sec)

******


Photo by Nathan Dumlao on Unsplash

Comments

  1. Süz18 March 2021 at 21:29

    Hello,
    In June 2011, you asked a question on the Blogger forum about adding New Post/Older Post buttons to your Contempo Theme blog. I followed the answer and the Newer Post, Older Post buttons are now located in pagination. I would like to also locate these buttons at the bottom of each opened individual post, as I see you have here, so that I can move directly from one post to the next, or the previous. I am, sadly, not a coder, and would appreciate some direction on where I should place similar code to achieve this. And any CSS that would go along with that. I am using the Contempo Theme as well. Assistance greatly appreciated :)

    ReplyDelete

Post a Comment

Popular

SLEEP thread causing "Waiting for table metadata lock"

By
Image
SLEEP thread causing "Waiting for table metadata lock" We might have faced some scenarios once our db connection threads are getting locked and we try to find the culprit thread id which is locking the thread, to kill and release the connections.  Here I am going to focus on one of the scenarios when db connection threads are locked at state " waiting for table metadata lock " and when we see the processlist, we can't find any thread which is running and using the same table, i.e., all threads are in SLEEP state except the locked threads. Such as :  mysql [localhost:5726] {msandbox} (world) > show processlist\G *************************** 1. row ***************************            Id: 5          User: rsandbox          Host: localhost:60624            db: NULL       Command: Binlog Dump       ...
Read more

MySQL Memory Calculator

By
Image
MySQL Memory Calculator Check out the “ MySQL Memory Calculator ” added to my blog page, which will be helpful to calculate MySQL memory usage during tuning of MySQL memory parameters. https://www.abhinavbit.com/p/mysql-memory-calculator.html Photo by  Kelly Sikkema  on  Unsplash
Read more

How to create CentOS VM using Vagrant

By
Image
Create CentOS VM using Vagrant 1. Download and install the latest Oracle VM VirtualBox.  https://www.oracle.com/technetwork/server-storage/virtualbox/downloads/index.html Like (For Mac OS X) https://download.oracle.com/virtualbox/6.0.6/VirtualBox-6.0.6-130049-OSX.dmg 2. Download and install the latest Vagrant. https://www.vagrantup.com/downloads.html Like (For Mac OS X) https://releases.hashicorp.com/vagrant/2.2.4/vagrant_2.2.4_x86_64.dmg 3. Download " centos /7" Vagrant Box using below command. abhinavs -Air : ~ agupta$ vagrant box add centos /7 ==> box: Loading metadata for box ' centos /7'      box : URL: https://vagrantcloud.com/centos/7 This box can work with multiple providers! The providers that it can work with are listed below. Please review the list and choose the provider you will be working with. 1) hyperv 2) libvirt 3) virtualbox 4) vmware_desktop Enter your choice: 3 ==> box:...
Read more

errno: 24 - Too many open files

By
Image
errno: 24 - Too many open files You might see this error inside MySQL's error log file or during mysql_upgrade operation. Can't open file: ‘./db/table.frm' (errno: 24 - Too many open files) To solve this issue, you will need to change the open files limit at system and db service level. --> To check and change this limit at the system level, we use ulimit client tool to set it dynamically. * Check current system open file limit. root@test:~# ulimit -a core file size          (blocks, -c) 0 data seg size           (kbytes, -d) unlimited scheduling priority             (-e) 0 file size               (blocks, -f) unlimited pending signals            ...
Read more

How to properly shutdown MySQL before any maintenance activity

By
Image
How to properly shutdown MySQL before any maintenance activity We might have different scenarios once we need to stop MySQL service before performing either server or database activity like patching/upgrade.   Before performing such activity, we need to make sure that we stop MySQL service properly to avoid any unforeseen crashes once our maintenance activity complete and MySQL service is started.  Here I would like to share the below steps which should be performed and take care to properly stop MySQL service.  Step 1: Ensure we don't have any long-running queries. Manually verify by checking the processlist. show processlist;  Step 2: If it is the master node, then ensure to stop application write hits on the database by doing either stop an app and put in maintenance OR if we have any failover solution then move write hits on another node.  Step 3: If it is a slave node, then STOP replication and note down t...
Read more

set --server-id to enable either a master or a slave

By
set --server-id to enable either a master or a slave Below issue can be faced, when we run CHANGE MASTER command to setup replication. mysql> change master to master_host='xx.xx.xx.xx',master_user='rep_user',master_password="xxxxxxx", master_log_file='db-01-test-bin.000064',master_log_pos=95854072,master_auto_position=0; ERROR 1794 (HY000): Slave is not configured or failed to initialize properly. You must at least set --server-id to enable either a master or a slave. Additional error messages can be found in the MySQL error log. Solution :- Here It is assumed, We have already set server-id parameter value different on master and slave node but still, we have the above error. It happens once, you performed the server packages upgrade(like from 5.6 to 5.7) and just started MySQL service and going to run CHANGE MASTER command. So, to solve this issue, Run mysql_upgrade command to update/upgrade system tables and then restart M...
Read more

ERROR 1040 (HY000): Too many connections

By
Image
ERROR 1040 (HY000): Too many connections An application might face this issue when all the defined max_connections parameter value is exhausted.  mysqld reserve a  +1 connection (i.e., max_connections + 1) for the user who is having the SUPER privilege.  When this issue appears, Only the user with the SUPER privileges can be connected if any other user who has SUPER privileges is not already connected to the database and we have reached max_connections.  1. Always make sure to DON'T give the SUPER privilege to any application user or any user which is being used inside the scripts. Because if that user has already been connected to db when "too many connections" issue appears, then that time root user can't be connected even though root user is having all privileges along with SUPER privileges.  Here I am presenting 3 cases which will help us, how MySQL handles "too many connections" and reserve 1 connection. For below example,...
Read more

GTID Replication (Skip Transaction using empty transaction)

By
Image
GTID Replication (Skip Transaction using empty transaction) To skip SQL thread's error in GTID replication setup, Insert empty transaction. PROBLEM :  db -test (none ) > show slave status\G *************************** 1. row ***************************                Slave_IO_State: Waiting for master to send event                   Master_Host: xxxxx                   Master_User: rep_user                   Master_Port: 3306                 Connect_Retry: 60               Master_Log_File: db -test-02-bin . 006725           Read_Master_Log_Pos: 4508785                Relay_Log_File: db -test-relay-bin . 000015         ...
Read more

Master has purged binary logs containing GTIDs that the slave requires

By
Master has purged binary logs containing GTIDs that the slave requires Problem :  Last_IO_Error: Got fatal error 1236 from master when reading data from binary log: 'The slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, but the master has purged binary logs containing GTIDs that the slave requires.' Solution : stop slave; Query OK, 0 rows affected (0.00 sec) CHANGE MASTER TO MASTER_AUTO_POSITION = 0; Query OK, 0 rows affected (0.01 sec) start slave; Query OK, 0 rows affected (0.00 sec)
Read more

How to Prepare for MySQL Certification Exam

By
Image
How to Prepare for MySQL Certification Exam Here I am going to suggest MySQL DBA, student or any newbie that how they can prepare for "Oracle's MySQL 5.x Database Administrator" certification exam.  Step 1: Lab -- Prepare your local MySQL lab environment and make sure to install the respective MySQL version on your lab. (i.e., if you are going to appear on MySQL 5.6 DBA exam 1Z0-883 then install MySQL 5.6 on your lab)  -- You can follow my below blog post to create your local MySQL lab environment.  How to create CentOS VM using Vagrant Install MySQL on CentOS using DBdeployer Step 2: Book + HandsOn Experience -- If you don't have below book, then go right now and purchase this book. (Here Please, you don't judge that below-suggested book is for 5.0 version whereas you are going to prepare for MySQL 5.6/5.7 DBA certification exam. Just go ahead and purchase below book. In the end, you will definitely say it was your...
Read more