Docker for Serverless Applications

Declarative containers

Declarative containers could be considered as a technology in between a normal container and a container running on FaaS. Let's look at the following imaginary Dockerfile:

FROM openjdk:8COPY app.jar /app/app.jarCMD ["/opt/jdk/bin/java", "-Xmx2G", "-jar", "/app/app.jar"]

What do we see here? At the first time of reading, it would look like a normal Dockerfile. Yes, it is. But it's not a declarative way to define an application container. Why?

We already know that this is a Java application doing some work for us. But it has hardcoded some important and brittle configurations, for example, when openjdk:8 pinned the app to use only that implementation, while -Xmx2G limits the memory usage of the app.

All FaaS platforms ...