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Displaying posts with tag: Linux (reset)
MariaDB source visualisation with Gource

Gource is a tool which can take a source code tree and create beautiful visualisations out of it. I’ve used it a few times before for various projects. This weekend I spent a little bit of time playing with it and applying it to MairaDB Server to see what it would produce.

The end result can be seen on YouTube.

In this visualisation you can see every file in the source code as a coloured dot. The dots are clustered in directories which are linked together in the directory tree using the lines. Git users swam around the files and spray code into them. It gives you a real sense of just how much work goes into a project.

To create this I got the MariaDB tree from GitHub and switched to branch 10.3. I observed the first MariaDB 5.1 tag was on the date 26th …

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How to convert galera node to async slave and vice-versa with MariaDB Galera Cluster.

Recently, I was working with one of our customer and this is what their requirement as they want to automate this process for converting galera node to async slave and make async slave to galera node without shutting down any server. ———- Here are the steps for how to do that. I assumes that you already have working 3 nodes galera cluster if not, then for the testing purpose you can create it from my previous post. setup-three-nodes-mariadb-galera-cluster-on-single-server-with-mysql-sandbox ———- Btw, there is no matter how many nodes you have. Now, create one test1 table and add 3 records in galera cluster.

MariaDB [nil]> select * from test1;
| id   | name      |
|    1 | nilnandan |
|    2 | joshi     |
|    3 | niljoshi  | …
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Making Maxscale/ProxySQL Highly Available ( 2 > 1 )

As Mydbops we are implementing Load Balancer using Maxscale or ProxySQL ( Our presentation ) for lot our client,  but these load balancers will become a SPOF (Single Point of failure) .  We have tried to explore services like HAProxy, Nginx, and Keepalived etc. Except Keepalived, all the services need to run on the standalone instance and  did not satisfy our exact need.

Keepalived does not requires any standalone instance, it can be deployed and configured with a minimal effort and provide the HA Solutions to the DB Infra. This approach not only fits for our DB setup, we can implement same …

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CPU Utilization is Not a Useful Metric

Once upon a time CPU utilization was quite a useful metric. Following are the output of several tools that provide CPU utilization metrics:


top reports a load of 1.66.

Is this correct? No. The correct load number is probably closer to 2.4.

# top -b -n 1| head -20
top - 11:27:45 up 151 days,  1:55,  7 users,  load average: 1.66, 1.84, 1.88
Tasks: 389 total,   3 running, 386 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.7%us, 20.6%sy,  1.2%ni, 77.3%id,  0.1%wa,  0.0%hi,  0.1%si,  0.0%st
Mem:  32639636k total, 32206476k used,   433160k free,   235732k buffers
Swap: 16359420k total, 10285664k used,  6073756k free,  2354840k cached

16702 root      20   0 8274m 5.0g 5.0g S 85.1 16.1  59164:55 VirtualBox
 4657 root      20   0  9.8g 5.2g 5.1g S 45.5 16.6  26518:13 VirtualBox
 6239 root      20   0  9.8g 5.1g 5.1g S 39.6 16.5  31200:52 VirtualBox
27070 root …
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Donkey System

Donkey system is a fully automatic MySQL database change system.
It gives a great help both to the release of the business and the company’s automated operation and maintenance.


HashiCorp Nomad and App Deployment with MySQL

We started our series on MySQL Docker deploments by showing how to deploy and use MySQL locally with docker-compose in Docker Compose and App Deployment with MySQL. Docker-compose itself is limited to one machine and it does not solve cross-node networking or span multiple datacenters. This is a job for so called cluster schedulers, i.e. […]

Three client error messages that MySQL DBAs should know by heart to save time

Working in an operations environment means that you get a lot of questions.  There’s the inevitable troubleshooting tasks that go along with being a DBA.  This is designed to be a quick reference post, much like my more in depth post in 2016 about timeouts. These typical error messages can create confusion and unneeded activities to diagnose.  To aid my own process of elimination and those of others, here are three error messages every DBA should know by heart.

SQLSTATE[HY000] [2002] Connection timed out

Plain and simple: this error means the client cannot connect to the server.

  • The calling program is trying to connect to the wrong database server (one that it cannot reach).
  • The database server is completely down (you’d get another error if the server and client actually made a connection). …
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Ulimit conflict with PAM and Systemd​​​

As a part of the MySQL Support, we had a support request from a client.The issue is DB server runs out of open files limit, though it is configured. It causes the DB hang and crash at times. Sometimes they can’t able to fix. So we plan to write our experience with configuring. We believe this article can help in configuring appropriate Ulimit value without any obstacles. Let us jump to the subject. What are the errors we might face while ulimit is not properly configured?

  1. Too many open files
  2. System unable to allocate necessary resources for the monitor thread
  3. can’t create new thread, closing connection

The above-shared list is just sample’s, maybe people who currently reading this blog may also face issue related to ulimit, for that they may have different debug …

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Hands-On Look at ZFS with MySQL

This post is a hands-on look at ZFS with MySQL.

In my previous post, I highlighted the similarities between MySQL and ZFS. Before going any further, I’d like you to be able to play and experiment with ZFS. This post shows you how to configure ZFS with MySQL in a minimalistic way on either Ubuntu 16.04 or Centos 7.


In order to be able to use ZFS, you need some available storage space. For storage – since the goal here is just to have a hands-on experience – we’ll use a simple file as a storage device. Although simplistic, I have now been using a similar setup on my laptop for nearly three years (just can’t get rid of it, it is too useful). For simplicity, I suggest you use a small Centos7 or Ubuntu 16.04 VM with one core, 8GB of disk and 1GB of RAM.

First, you need to install …

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Docker Compose and App Deployment with MySQL

In this post we show how to use the mysql-server Docker image for local development. We first introduce a simple example app that starts up and tries to connect to a given db until successful. We then show how to start containers for multiple MySQL versions and use our example app to connect to them. […]

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