| Totally agree here: the patterns and the tooling are not quite there yet. The concerns you raised are exactly the areas we struggled in when we moved to Docker. Our newer apps tend to be written with containerization in mind, though we also wanted and are porting older/legacy apps to take advantage of containers. 1. I somewhat liked 12factor's env-vars-as-config for its simplicity and ease of use but there are limits to its flat key-value string-only structure, not to mention the debatable security concerns that may arise when storing secrets in them. 2. Some apps, esp legacy ones, need files for their config, especially those that are costly/harder to rewrite/reintegrate. Config files benefit from being easily versioned, can be templated (Ansible's jinja ftw!), not to mention the richness of syntax/structure in can give (xml/yml/json/bin/etc). 3. We sometimes do a hybrid approach of doing a "source envfile.sh && exec binscript" as entrypoint of our containers, with envfile living in a mounted volume, managed by a CM tool. 4. There are lots of innovation here in specialized tools such as confd/etcd/consul/skydns but completely agree that versioning is a real concern. I like the heroku/deis-style approach of creating a new release for each change in the config. Bonus points to easy rollback on a previously working config (whatever system you're using, be it env files or config files). 5. As with projects/whole-stacks of multiple containers/hosts, I like the rancher/maestro-ng/docker-compose style of managing your system stack. Next wishlist for this would be a stack with support for pinned versioned docker images + smart rollback/rollfwd support for each config change anywhere in the stack. Ansible filled this gap for us: we have a git repo per project, various playbooks for deployment/lifecycle-management of docker containers, with multiple environments supported (dev/qa/prod using same playbook), support for multiple maintainers and secrets management via ansible-vault.
This is workable for us on a few projects, with small scale/set of hosts/containers. |