"Misconception: You should have only one process per Docker container!"<p>as soon as you start treating docker images as anything other that isolated statically compiled executables, you're not going to get the best out of docker.<p>if you are bundling inits, crons and companion apps into a single container then you need to stop, go back and either re-factor your code, or go to Full on VMs,<p>why?<p>because the networking is terrible. There are three great advantages to using real VMs over containers:<p>o Networking<p>o Isolation<p>o hot migration and resource allocation<p>Networking:<p>every instance of a service can have its own IP, and can be trivially tied to DNS automatically. scoped service discovery that's only sortof just possible now. however it uses immature tools with limited professional experience to back them up. DNS, DHCP with subdomains means images can be dropped in without any hard work<p>Isolation:<p>Its far harder to break out of a VM than it is a container. Especially if you are dealing with persistent storage and need to allow a container to write outside of its own chroot.<p>Hot migration:<p>This is killer. Hardware fails. having a cluster that automatically migrates around contention <i>and</i> hardware failure, without the app having to worry is worth many thousands of man hours. Yes making your own clustering system is fun, but its really quite hard to do well. Why bother when the hypervisor can do it for you?<p>There are three things going for docker:<p>Configuration library:<p>There is a rich library of prebuilt images<p>Baked in fudges:<p>You can bake in your dirty hack into the container, so long as you script it into your build job, its repeatable.<p>Speed:<p>yes there is less overhead. but lets be honest, how often have you hit up against VM speed issues that were down to your machine using too much CPU/memory? (if you're on AWS, no, you've not. AWS is dogshit slow, and expensive.)<p>Everything else, like immutable builds, easy dev environments et al, can be achieved already, and without much work.