10 Aug

Performance evaluation between different Druid roll-up levels

Introduction

In most datasets with a large number of events, going through individual events is less important. Most of the data use cases are around the summarized data. Druid summarizes this raw data at ingestion time using a process refer to as “roll-up”. Roll-up is the highest granularity of the data and will be able to query only up to the roll-up granularity. However, there are some scenarios where it’s important to have more granular data. However keeping more granular data comes at a cost. We did a small experiment to identify how different roll-up levels affect performance.

Rolling up data can dramatically reduce the size of data that needs to be stored (up to a factor of 100). Druid will roll up data as it is ingested to minimize the amount of raw data that needs to be stored. This storage reduction does come at a cost; as we roll up data, we lose the ability to query individual events. Phrased another way, the rollup granularity is the minimum granularity you will be able to explore data at and events are floored to this granularity. Hence, Druid ingestion specs define this granularity as the queryGranularity of the data. The lowest supported queryGranularity is millisecond. -http://druid.io

Dataset and Setup

We choose a CSV data set with millions (150M+) of records which contain sales data spanning across 2 years. CSV file was around 6 GB in physical size. This is a narrow data set with 3 dimensions and 2 metrics. We had 2 servers where all the components are deployed.

m4 large – Coordinator, Brokers, Overload nodes
r3 large – Middle managers and Historical nodes

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02 Jul

Suzuki WagonR Hybrid (Stingray) – Fuse design (Identifying and changing the blown fuse)

Introduction

We all come across some situations where some electronic features are not working suddenly. Most of the time it relates to a blown fuse. In this article, we talk about how to identify and replace a blown fuse. When doing this, it is always recommended to have a good idea about what functionalities relate to each fuse. So mainly in this article, we will talk about Suzuki WagonR Hybrid fuse design.

Where can we find the fuses in Suzuki WagonR Hybrid?

Mainly fuses found in five places. However, we are talking about three out five places where you will find fuses related to electronic accessories.

Under the Steering Wheel

Fuse design

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07 Jan

Sri Lanka Holidays Calendar 2017 for office365, Google etc. in ics format

As Everyone requested I added the Sri Lankan Holiday calendar for 2017 . Seems like this year is a good year in the terms of holidays (only till May 🙁 ). This will allow you to add the Sri Lanka Holidays Calendar 2017 to your digital calendar (Most of the online digital calendars that we use these days don’t have in built option to add the holiday calendar for Sri Lanka). Download ICS format 2017 Sri Lankan holiday calendar .

Adding to office365

Add calendar
From file (don’t go to holiday calendar, Sri Lanka is not available there)
Select file to upload and a calendar that holidays will be added (Create a separate new calendar is recommended. Use RED color)
Save

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02 Oct

Suzuki WagonR Hybrid (Stingray) – Tyre pressure / Air Pump

Introduction

If you are searching for this you might be checking the tyre pressure for the first time and trying to use your air pump for the first time. This article target the information related to this operation. Most of these information can be found in the manual (section 8-5)

Recommended tire pressure

Type	Size	Pressure	Remarks
Standard (Stingray)	155/65R14 75S	280 kPa (around 40 psi)	In manual it recommends tyre pressure of 41.6 Psi. This is mainly targeting the highways in Japan. However in Sri Lanka we face lot of rough road conditions and higher temperatures. So it is good to keep the tyre pressure around 35 Psi.
Standard	165/55R15 75V	240 kPa (around 35 psi)	In manual it recommends tyre pressure of 35 Psi. This is mainly targeting the highways in Japan. However in Sri Lanka we face lot of rough road conditions and higher temperatures. So it is good to keep the tyre pressure around 30 Psi.

This information is stickered on the car body near driver side door

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25 Sep

Application Aware Sharding for a MySQL Database

Introduction

When MySQL databases get too large, it become extremely hard to maintain as well as it reaches physical limits. Under maintainability issues we normally came across,

Taking too much time to ALTER a table
Became impossible to take dumps
Have to move tables to separate disks time to time
Etc.

If someone is looking for a database sharding as a solution, this maintainability issue must have exhausted him. In this article, I am going to share my personal experience in sharding a large MySQL database in real life. With the hands on experience on this large project, I am aware of lot of things related to sharding and organization level issue, concerns and limitations when you are going ahead with this project. This attempt is to go through the project from end to end so anyone who is about to do something similar can get benefit of my knowledge.
Before going to the article, I must share several things with you.

After this project, do not expect any performance gain on your day-to-day queries. This might actually add an additional overhead on your queries as your data will be shattered among multiple places. However, this will greatly improve the maintainability and will make sure that your data architecture survive in the fullness of time.
What I am going to talk about is application aware sharding and there are few other ways to do sharding in the data layer, which will be seamless to the applications. However, at the time of writing I did not find and tool that supports MySQL sharding in the DB level. Existing options are either not reliable or adds a large overhead on queries.
Sharding itself might not be the full answer for the problem. Sharding might need be accompanied with several sub projects that will supplement shading to reach its potential. This is feather explained the next section (“Problem and Solution”). I will be concentrating on the sharding project and will not explain much on the other supplementary projects.
You must be in a real need to do this project and you must have identified this as the only way to solve this problem before proceed because what you are going to start is a big project.
I have skipped some sensitive information as it relates to the company I am working for.

Problem and Solution

Problem: Data was growing in our MySQL database in rapid rates and we needed to make it constant as it lead to so many maintainability issues. With the amount of data grew bigger and number of queries per second was increased, there was even a possibility of downtimes. We needed to make the data volume in the MySQL a constant and keep it in a maintainable level.
Solution: We thought of partitioning the data and in the same time purging the old data to make size of data in one database somewhat constant. Therefore, there were two supplement projects carried out with the sharding project. One is to purge old data (purging project), and master data management (MDM project, moved some selected set of data to a central location). Data that could not be sharded due to various reasons and which global to the company was moved out, in the MDM project.

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09 Jul

Toastmasters Round Robin session, Round Robin Master Role and New ideas

What is round robin session and who is round robin master

Round Robin Session has been developed by the Toastmasters in Sri Lanka. This is a warm-up session that happens just after the introduction of the role players and just before the prepared speeches. Aim of this session is to improve the Speaking Skill and Listening Skill of members.

Round Robin Master is the person who leads this session by presenting a topic or a rolling story and handles its flow to make sure everyone gets the chance to speak up. This is highly important as this might be the only time that everyone gets the chance to speak up.

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04 Apr

Redis Sorted Object Set (Sorted Hashes)

We all know that best way to store object in Redis is through, Redis hashes. And Redis sorted sets are used to keep a sorted set with a give score for each value. What if we need a sorted set of objects? What we need is a “Sorted set of Objects” . Which Redis does not support by default. We came up with a hybrid, simple data structure that a allows sorted object using Redis Hashes and Redis Sorted-sets.

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01 Jan

Sri Lanka Holidays Calendar 2016 for office365, Google etc. in ics format

Its really important to track the holidays when you plan work ahead. But most of the online digital calendars that we use these days don’t have in built option to add the holiday calendar for Sri Lanka. Add the Sri Lanka Holidays Calendar 2016 to your digital calendar. Download ICS format SRI-LANKA-HOLIDAYS-2016 .

Adding to office365

Add calendar
From file (don’t go to holiday calendar, Sri Lanka is not available there)
Select file to upload and a calendar that holidays will be added (Create a separate new calendar is recommended. Use RED color)
Save

Read More →

10 Oct

Romantic Opera (රෝමාන්තික ඔපෙරාව) By Kasun Kalhara (Lyrics)

I looked for these lyrics all over the internet and finally i found it in a blog (http://dumbaat.blogspot.com/) and thought it requires a re-blog. This is one of my favorite songs.

හේමන්ත නිද්‍රාවේ, ගිලෙන හැන්දෑවක
නිසල තාවයේ මතුවෙන්නේ
ඔබේ දෑස පත්ලේ ඇවිලෙන, ප්‍රේම අද්‍යාශ යයි

සිහිනේ උමතු නිම්නේ, මා හුදෙකලාවේ නොහෙලා
ආදරේ දෙවඟන හැම රාත්‍රියකම, හැම හිමිදිරියක, හැම දහවලකම
වෙලී ගයන්න එනු මැනා සොප්‍රනෝ හඬින්

රෝමාන්තික ඔපෙරාවේ, හි සියුම් නාද සන් රචනයේ,
හැම ස්වරයකින් ම වෑ හේන්නේ, ඔබේ මගේ නොනිම් ප්‍රේමය යි.

සඳ දිය දහරාවේ, පෙඟෙන ලැමේ දෙයද,
නග්න තලාවේ මතු වෙන්නේ
ඔබේ සියුමැලි සිරුරේ උමතු ආලිංගනය යි

සිහිනේ උමතු නිම්නේ, මා හුදෙකලාවේ නොහෙලා
ආදරේ දෙවඟන සදහට ම එකට,
එක ආදරයක එක මිහිරියාව ක
ගිලී රඟන්න එනු මන දිනුම් මතින්

රෝමාන්තික ඔපෙරාවේ, හි සියුම් රංග වින්න්‍යාස යේ,
හැම රැඟුම කින්ම මැවෙන්නේ, ඔබේ මගේ නොනිම් ප්‍රේමය යි.

රෝමාන්තික ඔපෙරාවේ, හි සියුම් නාද සන් රචනයේ,
හැම ස්වරයකින් ම වෑ හේන්නේ, ඔබේ මගේ නොනිම් ප්‍රේමය යි.

හැම රැඟුම කින්ම මැවෙන්නේ, ඔබේ මගේ නොනිම් ප්‍රේමය යි.

19 Jul

[Scrum] Adding new priorities to the current sprint

We see changes in priorities time to time. With the nature of the team, you might need to expect newer priorities even in the middle of a sprint. New priorities might come as a production issue or a new feature development with higher ROI. I work in a service team where we get high priority items all the time. In this article, I like to talk about how we handle those issues.

What is the ideal way to handle Additional Requirements [real scrum way]

Once a sprint begins, you cannot add requirements or stories to the backlog

It is simple as above; simply you cannot add additional requirements to the sprint once the sprint begins. In addition, you need to keep in mind that if you do not obey at least one rule in scrum, you cannot tell that you are following scrum. Therefore, if you really need to be in pure scrum you need to close the current sprint and prioritize the backlog and start a new sprint with new priority list.

Ideal way doesn’t seems to be efficient for us

As you might already know there are so many hybrid versions of scrum due to scrum been inefficient in some situations. In our case, some team members that get so many ad-hoc tasks (related data base administration). Being a service team, all that members get some amount of ad-hoc tasks. We decided to fork the original scrum and make our own version of it, in search of better efficiency.

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