CamundaCon 2019: @berndruecker on Zeebe and microservices
Blog: Column 2 - Sandy Kemsley
Camunda co-founder Bernd Rücker presented on some of the implementation issues with microservices, in particular following on from Susanne Kaiser’s keynote with the theme of having small delivery teams spend more of their time developing business capabilities and less on the “undifferentiated heavy lifting” infrastructure bits required to support those. This significantly reduces the cognitive load for the team, allowing them to build the best possible business capabilities without worrying about arcane configuration details. Interestingly, this is not that different from the argument to move from a business process embedded within a business system logic to an externalized process in a BPMS — something that Bernd has a long history with.
He went through an example of the services behind a train ticket booking, which requires payment, seat reservation and ticket generation services; there are issues of latency and uptime as well as the user experience of how the results of those services are presented to the customer. He referenced the Reactive Manifesto as a guideline for software design patterns that are “more robust, more resilient, more flexible and better positioned to meet modern demands”.
Event-driven choreography is a common pattern these days, but has the problem of not being able to visualize the overall process flow between services. This can be alleviated somewhat by using event monitoring overlaid on a process model — effectively process discovery if the flow is not standardized or when it changes — or even more so by orchestrating standard parts of the flow to combine event-driven and orchestration patterns. Orchestration has the advantage of relocating the coupling between services in an event-driven flow to the orchestration layer: although event choreography is seen as loosely-coupled, there’s a lot of event listening that has to be built into the services, which couples them more closely. It’s not that one is good and the other bad: there’s a place for both choreography and choreography patterns in software development.
He finished with a discussion of monolithic legacy software and how to deal with it: from the initial step of just adding APIs to access functionality, you gradually chip away at the monolith’s capabilities, ripping them out replacing with externalized services.