“Microservices are easier than you think and more valuable than you’ve heard.” Those are the words of Ben Gracewood, chief delivery officer at cloud POS and omnichannel retail provider Vend. His company has used microservices to trim a monolithic PHP application, improving performance and changing the way the company approaches updates.
Approaching Microservices
Vend is currently used by 15,000 retailers in more than 180 countries. It is aimed at inventory-based retailers—think housewares, fashion, grocery and so on. In addition to the usual POS and payments facilities, Vend handles loyalty schemes, gift cards and online storefronts. The company is based in New Zealand, with offices in London, Melbourne, San Francisco and Toronto. Engineering and DevOps is done in Auckland.
Its global customer base means there is no maintenance window, and so live updates are essential.
Vend’s HTML5 and iOS clients include caching and a local database to allow offline operation (the data is subsequently resynchronized), primarily to allow users to keep working in situations where there is no Internet connection. The main system was originally a monolithic PHP application.
Vend executives had discussed the idea of migrating to microservices for about a year. But when the company’s vice president of Architecture experimented by writing one read-only microservice that improved performance by orders of magnitude, “This was the ‘a-ha’ moment for us,” Gracewood says.
Later, when Vend migrated from Rackspace to Amazon Web Services, it used a routing microservice that directed traffic to whichever cloud held that particular customer’s data at the time. That allowed a progressive migration with no disruption for customers.
Those initial successes showed Vend it should move more seriously in that direction. Nine months later, the company had 12 microservices in production.
Vend is now adding them at the rate of about two per month, and the monolithic PHP system has been slimmed and surrounded by a cloud of microservices. An Nginix-based routing layer allows existing URLs to be redirected to microservices where appropriate.
The company has followed DevOps practices from the outset, but its first few microservices were deployed and managed as special cases. Now, both the PHP monolith and all the microservices are within the DevOps tent.
Adoption Dos and Don’ts
When it comes to adopting microservices, “It’s never too soon to start,” says Gracewood. “It doesn’t have to be all or nothing,” despite what you might hear from other microservices veterans—everyone has been partway through their journey at some stage.
Gracewood’s advice is to build your first microservice and do what you have to in the development of your DevOps practice. Then keep iterating.
Don’t fall into the trap of thinking a microservice has to be 100 percent complete before it can be deployed, he says. Start by developing the minimum functionality required at the outset, and then increasing its sophistication over time. Since a change to a microservice affects a relatively small part of the entire system, the continuous update model is easier to apply to microservices than monolithic applications.
That point also has an organizational impact: A microservices architecture and DevOps support Gracewood’s philosophy of trusting engineering and development teams to implement the right things at the right time. With monolithic software, a mistake or a poor decision can have wide-ranging repercussions, so considerable oversight is required. But the nature of microservices keeps issues localized, so if an issue does somehow slip through the testing process, it is easier to revert to the previous version.
Adopting DevOps and microservices does require a certain amount of education, Gracewood notes. Engineering teams must understand the command line, Docker and so on. Making the move calls for “lots of tooling or lots of training,” he says. To that end, Vend has built some custom tools.
Gracewood’s final tip for organizations thinking of adopting microservices: “Log everything [and] apply metrics to everything,” right from the start. You need to know how people are using your system. In particular, identifying the most heavily used microservices will reveal the areas where efforts to improve performance are likely to yield the best returns.
