Comparison
Ephemeral container filesystemvsTwelve-factor app
Ephemeral container filesystem
the uploaded files were there all afternoon and gone after a restart, because they were written inside the container.
The rule that everything a container writes outside a mounted volume is discarded when it stops. It is deliberate — it is what makes a container replaceable — and it is the single most common surprise for an application ported from a virtual machine. It also has a capacity dimension: unbounded local writes fill the node's disk and get the workload evicted, taking well-behaved neighbours with it.
Full entry →Twelve-factor app
configuration comes from the environment, logs go to stdout, and the same image runs in staging and production unchanged.
A set of conventions for applications that are going to be run as disposable processes by a platform: config in the environment, backing services as attached resources, stateless processes, logs as a stream. It predates containers and describes them almost exactly, which is why it is still the fastest way to explain why an application resists being containerised. The failures it names are concrete — a config file baked into the image, a process that writes logs to a path, a session held in local memory.
Full entry →