Scaling Delayed Job for High Throughput Services

By Tafadzwa Pasipanodya on Sep 3, 2019 8:14:29 AM

A challenge often faced in multi-tenant SaaS is ensuring that each tenant gets a fair share of a platform's resources. At Salsify, we had to address this in our Delayed Job-based background task execution infrastructure. Because our customers have different use cases, they tend to run tasks of varying complexity and size. Over time we developed tenant-fairness job reservation strategies that made scaling our job system difficult if not impossible. In this post, I discuss how we managed to extend Delayed Job to solve for tenant fairness in a scalable manner.

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Essential Ember Addons: The State of the Ember Addon Ecosystem in 2019

By Ron. A on Jun 28, 2019 9:45:00 AM

2019 has been a great year for Ember so far, so while my peers are focused on setting direction for the framework for the rest of 2019, I wanted to take stock of the existing addons ecosystem.

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Finding the most recent item by group in Rails

By Stephen Karger on Jun 21, 2019 9:09:03 AM
A certain kind of question comes up sometimes when building an application with a relational database:
What is the most recent item for each category?
It often happens with a one-to-many table relationship. You might have a departments table and an employees table, where a department has many employees, and you would like to know each department's most recently hired employee.
The general version of this question even has a name, Greatest N Per Group, and it's not limited to one-to-many relationships, nor to most recent items. Nevertheless, that example is broadly useful because it arises naturally when inserting records into a DB table over time. In this post I'll show the query using standard SQL and walk through integrating it into Rails. Read on for details!

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Ember in 2019: Tearing Down "Us and Them"

By Dan Freeman on Jun 11, 2019 8:30:22 AM

I'm writing this near the end of the official #EmberJS2019 window, which means a lot of what there is to say has already been said. As I've read through this year's posts, there are a handful of themes I see coming up over and over again:

  • streamlining and modularizing the framework
  • broadening the Ember community
  • landing our new build system, Embroider

These points are each important and valuable in their own right, and I'm hopeful that the 2019 Roadmap RFC will address all of them. Many of the posts discussing them, though, brush up against something that I think merits a more explicit discussion.

Over the past couple years I've seen an increasing number of Ember folks display a mentality that divides the world into Us and Them. It manifests in social media interactions and blog posts, day-to-day chatter in the Ember Discord server, and even the way we frame meetup and conference talks. I think it's driven by a desire to see Ember succeed and to convince other people that they should like this thing as much as we do, but it ultimately does everyone involved a disservice.

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Our Journey from Heroku to Kubernetes

By Salsify DevOps on Dec 20, 2018 2:08:00 PM

The Decision

We, like many small startups, had started our application on Heroku, and had built up considerable technical and social practice around its use. About 18 months ago, the Engineering team here at Salsify recognized that as our team, product, and user base continued to grow, we would outgrow the ideal case for Heroku.

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A Safer Rails Console

By Timothy Su on Feb 5, 2018 1:49:06 PM

A Safer Rails Console_Salsify.jpeg

One of the blessings and curses of Rails development is the ability to use Rails console for debugging issues and inspecting data. The console is oftentimes used in a production environment, as it is the quickest method to glean information about any problems. With great power comes great responsibility: A command that attempts to reset a local developer environment by deleting all records of a model could easily be input into a production console. In addition, with potentially unknown clipboard data (thanks "copy-on-select"), any valid Ruby code with line breaks will automatically be executed if pasted. Any user who is deleting models, queuing up events, and updating records accidentally or intentionally should be made aware of the implications. At Salsify, we've solved this problem using a combination of open-source and home-brewed improvements and rolled them into a handy gem. Read on to learn more!

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Fancy trees with botanist

By Keith Williams on Jun 14, 2017 2:21:28 PM

Have you ever wanted to build your own calculator, query language, or even web browser? Parsers and Transformers are tremendously useful for these applications and many more, and thanks to tools like Salsify's own Botanist you don't need to be an expert in compiler design to work with them.

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Organizing Data Flow with Ember

By Devers Talmage on Apr 11, 2017 1:38:23 PM

One of the most important core principles of developing with Ember is "data down, actions up." You might see this concept abbreviated as DDAU in various Ember communities. The main premise of DDAU is that data should flow down through your component hierarchy (passed through and potentially modified by various components), while changes to said data should be propagated back up through that hierarchy via actions.

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Adventures in Avro

By Tim Perkins on Jun 13, 2016 8:11:57 AM
As part of our microservices architecture we recently adopted Avro as a data serialization format. In the process of incorporating Avro we created a Ruby DSL for defining Avro schemas, developed a gem for generating models from Avro schemas, and reimplemented an Avro schema registry in Rails. Here’s how we got there ... 
Here’s a situation that may be familiar: at Salsify we are moving towards a microservices architecture. Have you done that too? Are you thinking about doing it? This is a pretty common progression for startups that built a monolithic application first, found great market fit and then need to scale both the application and the team. At Salsify, we already have quite a few services running outside of the original monolith, but several months ago we started to define an architecture for how we should chip away at the monolith and structure new core services.
Naturally part of the architecture we are defining is how services should communicate with each other. For synchronous communication, we decided to stick with HTTP REST APIs that speak JSON. For asynchronous communication, we selected Apache Kafka.
We evaluated several data serialization formats to use with Kafka. The main contenders were Apache Avro, JSON, Protocol Buffers and Apache Thrift. For asynchronous communication we wanted a data format that was more compact and faster to process. Asynchronous data may stick around longer and the same message may be processed by multiple systems so version handling was important. A serialization system should also provide additional benefits like validation and strong typing.
At this point, I should inject that we’re primarily a Ruby shop. We love our expressive, dynamic language of choice, so a big factor in the selection process was how well the framework integrates with Ruby. Based on the title of this post, it's not going to be any surprise which option was the winner ...

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Delayed Job Queue Fairness

By Robert Kaufman on May 23, 2016 1:06:13 PM
At Salsify, we use Delayed Job extensively to handle asynchronous tasks. This works well for us, as it means we can finish web requests faster, resulting in a more responsive web app, while offloading non-urgent tasks to background jobs. For the most part, Delayed Job (and similar job queuing mechanisms like Resque, Celery, etc.) provide a simple and highly effective approach for running background work, making sure that it gets done, and providing a framework to scale your compute resources to handle expected workloads. Even beyond that, these frameworks create straightforward opportunities for dynamically scaling resources to handle spikes in workload. For example, we use an excellent service called HireFire to dynamically scale our Delayed Job worker pools based on queued work. Meaning, we can meet the needs of changing workload while keeping our hosting costs reasonable.

But despite all of the advantages of running background jobs, under real world usage you can still run into challenging situations that require thoughtful handling. One general class of problems that can arise is achieving fairness in resource usage across users. 

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