Replication is the process that transfers data from an active master to a slave server, which reproduces the data stream to achieve, as best as possible, a faithful copy of the data in the master.

To check replication health, you may start with sampling the service, i.e. committing some Sentinel value in the master and retrieving it from the slave.

Sentinel data: Tap tap… Is this thing on?
If you want to make sure that replication is working, the easiest test is using replication itself to see if data is being copied across from the master to the slaves. The method is easy:

1. Make sure that the data you want to see is NOT in the master or in the slave. If you skip this step, you may think that replication is working, while in fact it may not.
2. Either create a table …

This post is likely gonna get less relevant when Magento 2 comes out, but I decided to put it out there any way. In my limited time working with Magento I’ve come across a couple scenario’s I wanted to touch on. Hope it’s helpful for anyone.

Let say a merchant wants a new Magento online store. Now, there are a couple scenario’s that are likely or less likely:

1. The previous store was built with Magento. Customers can easily be imported using the various tools available (Magmi, import/export, dataflow, etc.)
2. The previous store was built on a platform that stores passwords in plaintext - fortunately this is not very likely ;)
3. The previous store was built on a different platform, using different hashing algorithms.
4. The previous store was built on a different platform which happens to use the same hashing algorithm as Magento,
5. A combination of #3 and #4 (yes - I’ve seen it). …

Loading databases on virtual systems is not as straight forward as it should be. Last time the foundation for using Ansible was set down on our quest to be able to have fully functional database servers on virtual servers automatically. But that prompted a few of you to remind me that you do not always need Ansible.

Without Ansible
You can have Vagrant do the work. Modify the vagrant file to run a script to run a script when provisioned, such as
config.vm.provision :shell,path: "setup.sh"
and create the setup.sh shell script.

#!/bin/bash
#
# example setup script for LAMP stack on Vagant box
sudo apt-get -y update
sudo apt-get -y install apache2 php5 libapache2-mod-php5
## Set …

Similar to databases, the modern IT team is often distributed. As remote work increases and employee locations span the globe, it becomes difficult to keep everyone on the same page. Our latest time zone update is a step toward this goal.

In the past, all the dates and graphs have been shown in the user’s time zone. VivdCortex has members in Charlottesville and Montevideo, which adds a level of complexity. If you have members in San Fransisco, Auckland, and London, communicating can get really complicated.

While this is still the defult behavior, you can also set a fixed time zone for an environment, ensuring every team member is looking at the same time. This is especially helpful when trouble shooting, optimizing certain queries, collaborating after a code deploy… the list goes on.

The current time zone will be shown in the timepicker for easy reference, and every time we display a date, we will also …

While MONyog MySQL Monitor is being embraced by DBAs and DevOps around the world, we are constantly adding more features to make MONyog the most complete MySQL monitoring tool.

MONyog ships 40+ MySQL and system metric charts. It also lets you add custom charts. With the latest update, we have made Charts more powerful by adding few important features to help you find problem queries with ease.

Here’s a 1 minute video to walk you through the new features.

Existing customers can download MONyog 6.33 from Customer Area. To evaluate MONyog 6.33, please download a 14-day trial.

We are really excited about this update and we hope you like the new features. Please feel free to share your feedback.

Cheers,
Team MONyog

The post …

Houston, we have a problem. Google search for “What is innodb history list length?” and you get a bunch of nonsense mixed in with correct information, and it’s hard to tell which information is right. Let’s fix this.

What is InnoDB History, Anyway?

InnoDB is an MVCC storage engine, which means you can start a transaction and continue to see a consistent snapshot even as the data changes. This is implemented by keeping old versions of rows as they are modified.

They’re kept in a linked list. The most recent version points to the previous one, which points to the previous one, and so on. Each version has a transaction ID with it so when InnoDB goes looking for a row, it compares your current transaction ID to the row version and selects the right one for you. This can be done without locking.

MVCC is …

Recently we got request from our customer that something is going wrong with their database and they’re are getting strange errors after each insert or update to specific table. The strangeness caused by “Unknown column ‘column-name’ in ‘field list'” message while this column was existing in this table. Our investigation shown that this was caused by trigger on the table they were trying to do the insert/update. This trigger did the insert to another table where the mentioned column didn’t exist.

Let me show you example:

create test DB and 2 test tables:

create database test;
use test;

create table t1 (field1 int auto_increment not null, field2 varchar(10), field3 varchar(10), primary key(field1)) engine=innodb;
create table t2 (field1 int, field2 varchar(10)) engine=innodb;

Then create a new insert trigger on t1 table:

delimiter ##

create trigger insert_on_t1_to_t2
 after insert
 on t1 for each …

I've written two separate posts about the MySQL 5.6 temporal column format change, but I haven't yet addressed the problem with the way this upgrade was implemented. Essentially, the problem is that the implicit format upgrade causes a write-blocking full table rebuild the first time you run ALTER TABLE after upgrading, even if the ALTER TABLE command is an online DDL operation that normally doesn't block writes.

This behavior is well intentioned, but harmful. The intent is for the server to tack on a seemingly innocuous column format upgrade to my existing ALTER TABLE command, but when it changes my DDL from non-blocking …

We are pretty much raving fans of CircleCI and we are not ashamed to say it. Here’s why.

What Does CircleCI Do For Us?

It would be reasonable to describe CircleCI like this:

• continuous integration and testing
• compiles our code for us
• automated QA

But that misses the point, because what they really do is they help us delight our customers. And they don’t just provide tools or ingredients or recipes for this. They provide a solution. I know it’s a buzzword and I have avoided saying “solution” since back in the day when I was a .NET developer using Visual Studio. But it is the only word that describes what CircleCI does for us.

We have a hard challenge/problem: in order to provide the absolute best service for our customers, we must be able to ship improvements in minutes with confidence. …

Using MySQL Enterprise Monitor with the MySQL Enterprise Firewall

Using MySQL Enterprise Monitor 3.0.22, the following newly added variables for the MySQL Enterprise Firewall are added : Ref :  http://dev.mysql.com/doc/relnotes/mysql-monitor/3.0/en/news-3-0-22.html

• System Variables:
  
  • mysql_firewall_max_query_size
  • mysql_firewall_mode
  • mysql_firewall_trace
• Status Variables:
  
  • Firewall_access_denied
  • Firewall_access_granted
  • Firewall_cached_entries

For information about MySQL Enterprise Firewall, you can refer to the information on Web  …