Have you ever wondered what could happen if your MySQL database goes down?

Although it’s evident such a crash will cause downtime – and surely some business impact in terms of revenue – can you do something to reduce this impact?

The simple answer is “yes” by doing regular backups (of course) but are you 100% sure that your current backup strategy will really come through when an outage occurs? And how much precious time will pass (and how much revenue will be lost) before you get your business back online?

I usually think of backups as the step after HA fails. Let’s say we’re in M<>M replication and something occurs that kills the db but the HA can’t save the day. Let’s pretend that the UPS fails and those servers are completely out. You can’t failover; you have to restore data. Backups are a key piece of “Business Continuity.” Also factor in the frequent need to restore data that’s been …

Quite often, especially for benchmarks, I am trying to limit available memory for a database server (usually for MySQL, but recently for MongoDB also). This is usually needed to test database performance in scenarios with different memory limits. I have physical servers with the usually high amount of memory (128GB or more), but I am interested to see how a database server will perform, say if only 16GB of memory is available.

And while InnoDB usually respects the setting of innodb_buffer_pool_size in O_DIRECT mode (OS cache is not being used in this case), more engines (TokuDB for MySQL, MMAP, WiredTiger, RocksDB for MongoDB) usually get benefits from OS cache, and Linux kernel by default is generous enough to allocate as much memory as available. There I should note that while TokuDB (and TokuMX for MongoDB) supports DIRECT mode (that is bypass OS cache), we found there is a performance gain if OS cache is used for compressed pages.

For the majority of us who have grown accustomed to a Windows environment over the years, Linux can seem like another world. In essence, Linux is a free open-source operating system that has gained increasing popularity since its release in 1991. Linux is based on the whole Unix ecosystem of operating systems that grew out of Bell Laboratories in the early 1970s. Linux has been around for almost 25 years and grew immensely in the late 1990s and early 2000s when it became associated with the LAMP web development stack; Linux stands for the ‘L’ in the acronym of popular tools, along with Apache, MySQL, and PHP/Perl/Python.

The main difference that …

Mysql Incremental Backup is a complete incremental backup script for MyISAM and InnodB databases using the MySQL binary log so that the backup process does not affect running databases. This tutorial describes the installation of the MysqlIncrementalBackup script and helps to troubleshoot issues that may arise during setup.

Last week, I wrote about how to use bash arrays and the MySQL database to create unit and integration test scripts. While the MySQL example was nice for some users, there were some others who wanted me to show how to write bash shell scripts for Oracle unit and integration testing. That’s what this blog post does.

If you don’t know much about bash shell, you should start with the prior post to learn about bash arrays, if-statements, and for-loops. In this blog post I only cover how to implement a bash shell script that runs SQL scripts in silent mode and then queries the database in silent mode and writes the output to an external file.

I’ve copied the basic ERD for the example because of a request from a reader. In their opinion it makes cross referencing the …

Student questions are always interesting! They get me to think and to write. The question this time is: “How do I write a Bash Shell script to process multiple MySQL script files?” This post builds the following model (courtesy of MySQL Workbench) by using a bash shell script and MySQL script files, but there’s a disclaimer on this post. It shows both insecure and secure approaches and you should avoid the insecure ones.

It seems a quick refresher on how to use arrays in bash shell may be helpful. While it’s essential in a Linux environment, it’s seems not everyone masters the bash shell.

Especially, since I checked my …

Fedora comes with vim and gedit installed but the gedit installation is bare bones. You can update gedit to include supplemental Plug-ins with the following yum command as the root user:

yum install -y gedit-plugins

It generates the following log file:

Loaded plugins: langpacks, refresh-packagekit
mysql-connectors-community                                  | 2.5 kB  00:00     
mysql-tools-community                                       | 2.5 kB  00:00     
mysql56-community                                           | 2.5 kB  00:00     
pgdg93                                                      | 3.6 kB  00:00     
updates/20/x86_64/metalink                                  |  14 kB  00:00     
updates                                                     | 4.9 kB  00:00 …

The fsfreeze command, is used to suspend and resume access to a file system. This allows consistent snapshots to be taken of the filesystem. fsfreeze supports Ext3/4, ReiserFS, JFS and XFS.

A filesystem can be frozen using following command:

# /sbin/fsfreeze -f /data

Now if you are writing to this filesystem, the process/command will be stuck. For example, following command will be stuck in D (UNINTERUPTEBLE_SLEEP) state:

# echo “testing” > /data/file

Only after the filesystem is unfreezed using the following command, can it continue:

# /sbin/fsfreeze -u /data

As per the fsfreeze main page, “fsfreeze is unnecessary for device-mapper devices. The device-mapper (and LVM) automatically freezes filesystem on the device when a snapshot creation is requested.”

fsfreeze is provided by the util-linux package in RHEL systems. Along with userspace support, fsfreeze also …

While I previously blogged about installing Netbeans 8, some of my students would prefer to use the Eclipse IDE. This post shows how to install and configure Eclipse IDE, include the mysql-connector-java.jar, and write Java to access the MySQL.

You can download Eclipse IDE and then open it in Fedora’s Archive Manager. You can use the Archive Manager to Extract the Eclipse IDE to a directory of your choice. I opted to extract it into my student user’s home directory, which is /home/student.

After extracting the Eclipse IDE, you can check the contents of the eclipse directory with the following command:

ls -al eclipse

You should see the following:

There are tools like pt-kill from the percona tool kit that may print/kill the long running transactions at MariaDB, MySQL or at Percona data instances, but a lot of backup scripts are just some simple bash lines.
So checking for long running transactions before the backup to be executed seems to be a step that is missed a lot.

Here is one line that might be just added in every bash script before the backup to be executed
Variant 1. Just log all the processlist entries and calculate which ones were running longer than TIMELIMIT:

$ export TIMELIMIT=70 && echo "$(date) : check for long runnig queries start:" >> /tmp/processlist.list.to.kill && mysql -BN -e 'show processlist;' | tee -a /tmp/processlist.list.to.kill | awk -vlongtime=${TIMELIMIT} '($6>longtime){print "kill "$1";"}' | tee -a /tmp/processlist.list.to.kill

Variant 2: Log all the processlist, calculate the calculate which processes are …