Re-published from the Telia Tech Blog.

Continue reading →

---

Continue reading →

---

Cross-posted from Telia's Tech Blog.

We have had our mission-critical webapp running on AWS Elastic Beanstalk for three years and have been extremely happy with it. However we have now outgrown it and move to a manually managed infrastructure and CodeDeploy.

AWS Beanstalk provides you with lot of bang for the buck and enables you to get up and running in no time:

• Simple, no-downtime deployment and automatic roll-back based on user-provided health-check (either one subset of nodes at a time or blue-green deployment)
• Autoscaling
• Managed updates - security fixes and other improvements installed automatically
• Built-in HTTP Proxy with caching in front of your application
• Monitoring dashboard with alerting and access to logs without the need for SSH
• A list of past versions & ability to roll-back
• Support for many runtimes (Java, Node.js, Docker to name just a few)

So if you need a solid, state-of-the-art infrastructure for a web-scale application and you don't have lot of time and/or skill to build one on AWS on your own, I absolutely recommend Beanstalk.


Continue reading →

---

Cross-posted from Telia's Tech Blog

We use Amazon Web Services (AWS) heavily and are in the process of migrating towards infrastructure-as-code, i.e. creating a textual description of the desired infrastructure in a Domain-Specific Language and letting the tool create and update the infrastructure.

We are lucky enough to have some of the leading Terraform experts in our organisation so they lay out the path and we follow it. We are at an initial stage and everything is thus "work in progress" and far from perfect, therefore it is important to judge leniently. Yet I think I have gain enough experience trying to apply Terraform both now and in the past to speak about some of the (current?) limitations and disadvantages and to consider alternatives.


Continue reading →

---

Travis CI is a pretty good software-as-a-service Continuous Integration server. It can deploy to many targets, including AWS BeanStalk, S3, and CodeDeploy.

However it might happen that the deploy tool (dpl) has a missing feature or doesn't do exactly what you need. Fortunately it is easy to fix and run a modified version of the tool, and I will show you how to do that.


Continue reading →

---

Re-posted from Telia's tech blog.

What's the deal with ClojureScript? How can you justify picking such a "niche" language? I have recently experienced a "wow" session, demonstrating the productivity gains of ClojureScript and the interactive development it enables thanks to its REPL. I would like to share the experience with you. (If you have never heard about it before - it is a modern, very well designed Lisp that compiles to JavaScript for frontend and backend development. It comes with a REPL that makes it possible to reload code changes and run code in the context of your live application, developing it while it is running.)


Continue reading →

---

Goal: Simulate how a Node.js application reacts to timeouts.

Solution: Use toxiproxy and its timeout "toxic" with the value of 0, i.e. the connection won't close, and data will be delayed until the toxic is removed.

Continue reading →

---

The Parallel Change technique is intended to make it possible to change code in a small, save steps by first adding the new way of doing things (without breaking the old one; "expand"), then switching over to the new way ("migrate"), and finally removing the old way ("contract", i.e. make smaller). Here is an example of it applied in practice to refactor code producing a large JSON that contains a dictionary of addresses at one place and refers to them by their keys at other places. The goal is to rename the key. (We can't use simple search & replace for reasons.)


Continue reading →

---

Should we write stupid code that is easy to understand for newcomers? It seems as a good thing to do. But it is the wrong thing to optimise for because it is a rare case. Most of the time you will be working with people experienced in the code base. And if there is a new member, you should not just throw her into the water and expect her to learn and understand everything on her own. It is better to optimise for the common case, i.e. people that are up to speed. It is thus OK to expect and require that the developers have certain domain and technical knowledge. And spend resources to ensure that is the case with new members. Simply put, you should not dumb down your code to match the common knowledge but elevate new team mates to the baseline that you defined for your product (based on your domain, the expected level of experience and dedication etc.).

Continue reading →

---

Defensive programming suggests that we should add various checks to our code to ensure the presence and proper shape and type of data. But there is one important rule - only add a check if you know that thing can really happen. Don't add random checks just to be sure - because you are misleading the next developer.


Continue reading →

---

The WordPress.com stats helper monkeys prepared a 2015 annual report for this blog.

Continue reading →

---

Cross-posted from the TeliaSonera tech blog

Continue reading →

---

I have learned that it is costly to not prioritise expressing one's design concerns and ideas early. As a result, we have a shopping cart that is noticeably slow, goes down whenever the backend experiences problems, and is a potential performance bottleneck. Let's have a look at the problem, the actual and my ideal designs, and their pros and cons.

We have added shopping cart functionality to our web shop, using a backend service to provide most of the functionality and to hold the state. The design focus was on simplicity - the front-end is stateless, any change to the cart is sent to the backend and the current content of the cart is always fetched anew from it to avoid the complexity of maintaining and syncing state at two places. Even though the backend wasn't design for the actual front-end needs, we work around it. The front-end doesn't need to do much work and it is thus a success in this regard.


Continue reading →

---

Our team has struggled with slow calls to the back-end, resulting in unpleasant, user-perceivable delays. While a direct (HTTP) call to a backend REST service took around 50ms, our median time was around 300ms (while using HTTPS and a proxy between us and the service).

Continue reading →

---

Cross-posted from the TeliaSonera tech blog

Our UX designer and interaction specialist - a wonderful guy - has shocked us today by telling us that we (the developers) are moving too fast. He needs more time to do proper user experience and interface design – talk to real users, collect feedback, design based on data, not just hypotheses and gut feeling. To do this, he needs us to slow down.

We see a common human "mistake" here: where the expression of a genuine need gets mixed in with a suggestion for satisfying it. We are happy to learn about the need and will do our best to satisfy it (after all, we want everybody to be happy, and we too love evidence-based design) but we want to challenge the proposed solution. There is never just one way to satisfy a need – and the first proposed solution is rarely the best one (not mentioning that this particular one goes against the needs of us, the developers).


Continue reading →

---

Copyright © 2024 Jakub Holý
Powered by Cryogen
Theme by KingMob