There is a well known rule of thumb among microservices advocates that you should never share a database between microservices. This rule is, in my humble opinion, categorically wrong and still in most cases right. Software architecture is all about making trade-offs and so, anyone that considers themselves an architect should not take such rules at face value. This blog post is all about the trade-off.
Our systems today are typically distributed, and sometimes integrated via an event bus such as Kafka. We store data in a database and publish events to inform other systems of changes. For example, the system that stores a Thing is eventually consistent with the other systems that consume the ThingCreated event. This means that at some point the other systems will be in the state that they should reach when they find out about the new Thing. When systems fail to achieve this level of consistency, it often requires significant time for analysis, troubleshooting and consistency restoration. We would like to save ourselves this time and instead develop correct systems.
In this post I’m going to describe an issue we experienced with nginx and its handling of Server Side Includes (SSIs). We saw that nginx at first decodes the SSI URI path and afterwards encodes it when loading the resource. And in some cases, the URI path encoded by nginx was different than the original one. The solution is easy (use query parameters if in doubt), but I thought I’d share this so that others maybe don’t run into this issue and/or see how to debug such things.