17 Aug

Negombo Toastmasters Club 8th Installation Ceremony for year 2017/2018

Negombo Toastmasters Club 8th Installation Ceremony for year 2017/2018

Negombo Toastmasters held its eighth Executive Committee Installation Ceremony for 2017/2018 on 12 August 2017 at Paradise Beach Hotel, Negombo. The Chief Guest was DTM Arjuna ⁠⁠⁠Jayadarshana and the Guest of Honor was TM Sudath Fernando who is a charter member of Negombo Toastmasters Club. Area Director for District 89 Area H4 Sudath Ranaweera was also present at the occasion. Another two of our charter members TM Mohammed Marzook, Division Director TM Anura Perera also joined us on this important day.

Negombo Toastmasters Club 8th Installation Ceremony for year 2017/2018

The following officers for 2017/2018 were installed at the ceremony.

  • President – TM Tony Ukwattage
  • Vice President/Education – TM Bavanitha Rajagugan
  • Vice President/Membership – TM Gihan Wijayatilake
  • Vice President/Public Relations – TM Romesh Malinga Perera
  • Secretary – TM Tissera Maduranga
  • Treasurer – TM Buddika Liyanage
  • Sergeant-at-Arms – TM Shehan Gunasinghe

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10 Aug

Performance evaluation between different Druid roll-up levels


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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