To speed up deployments, we'll remove the healthcheck step.
This adds some risk to deployments for non-web roles - if they don't
have a Docker healthcheck configured then the only check we do is if
the container is running.
If there is a bad image we might see the container running before it
exits and deploy it. Previously the healthcheck step would have avoided
this by ensuring a web container could boot and serve traffic first.
To mitigate this, we'll add a deployment barrier. Until one of the
primary role containers passes its healthcheck, we'll keep the barrier
up and avoid stopping the containers on the non-primary roles.
It the primary role container fails its healthcheck, we'll close the
barrier and shut down the new containers on the waiting roles.
We also have a new integration test to check we correctly handle a
a broken image. This highlighted that SSHKit's default runner will
stop at the first error it encounters. We'll now have a custom runner
that waits for all threads to finish allowing them to clean up.
Docker does not respect the .dockerignore file when building from a tar.
Instead by default we'll make a local clone into a tmp directory and
build from there. Subsequent builds will reset the clone to match the
checkout.
Compared to building directly in the repo, we'll have reproducible
builds.
Compared to using a git archive:
1. .dockerignore is respected
2. We'll have faster builds - docker can be smarter about caching the
build context on subsequent builds from a directory
To build from the repo directly, set the build context to "." in the
config.
If there are uncommitted changes, we'll warn about them either being
included or ignored depending on whether we build from the clone.
Allow hosts to be tagged so we can have host specific env variables.
We might want host specific env variables for things like datacenter
specific tags or testing GC settings on a specific host.
Right now you either need to set up a separate role, or have the app
be host aware.
Now you can define tag env variables and assign those to hosts.
For example:
```
servers:
- 1.1.1.1
- 1.1.1.2: tag1
- 1.1.1.2: tag2
- 1.1.1.3: [ tag1, tag2 ]
env_tags:
tag1:
ENV1: value1
tag2:
ENV2: value2
```
The tag env supports the full env format, allowing you to set secret and
clear values.
When ssh options are set, they overwrite username and password passed as ssh builder uri. Passing part of uri for ssh-kit is fine, as it then properly extracts username and password and forwards it as host.ssh_options (in which case it's no longer empty)
Extract Kamal::Commander::Specifics to deal with host and role setup and
ensure that primary hosts and roles always come first. This means that
in a rolling deploy we deploy to the primary ones first.
This will be important when we remove the healthcheck step as we want
to confirm the primary host can be deployed to before completing a
deployment for other roles.
By setting the hosts and roles all together in one place we can sort
the primary ones to the front without creating infinite loops.
Currently the latest container is the one that was created last. But if
we have had a failed deployment that left two containers running that
would not be the one we want. The second container could be in a
restart loop for example.
Instead we want the container that is running the image tagged as
latest. As we now tag as latest after a successful deployment we can
trust that that is a healthy container.
In the case that there is no container running the latest image tag,
we'll fall back to the latest container.
This could happen if the deploy was halted in between the old container
being stopped and the image being tagged as latest.
If you are deploying more than one destination to a host, the latest
tags will conflict, so we'll append the destination to the tag.
The latest tag is used when booting the app or exec-ing a new container.
If a deploy doesn't complete on a host for all roles then we should
probably not be using it, so move the tagging to the end of the boot
process.
This will allow us to filter for containers that have no destination in
cases where we deploy an empty + a non empty destination to the same
host.
To note:
```
\# Containers with a destination label
$ docker ps --filter label=destination
\# Containers with an empty destination label
$ docker ps --filter label=destination=
```
Donal McBreen