Files
kamal/lib/mrsk/commands/app.rb
Kevin McConnell df202d6ef4 Move health checks into Docker
Replaces our current host-based HTTP healthchecks with Docker
healthchecks, and adds a new `healthcheck.cmd` config option that can be
used to define a custom health check command. Also removes Traefik's
healthchecks, since they are no longer necessary.

When deploying a container that has a healthcheck defined, we wait for
it to report a healthy status before stopping the old container that it
replaces. Containers that don't have a healthcheck defined continue to
wait for `MRSK.config.readiness_delay`.

There are some pros and cons to using Docker healthchecks rather than
checking from the host. The main advantages are:

- Supports non-HTTP checks, and app-specific check scripts provided by a
  container.
- When booting a container, allows MRSK to wait for a container to be
  healthy before shutting down the old container it replaces. This
  should be safer than relying on a timeout.
- Containers with healthchecks won't be active in Traefik until they
  reach a healthy state, which prevents any traffic from being routed to
  them before they are ready.

The main _disadvantage_ is that containers are now required to provide
some way to check their health. Our default check assumes that `curl` is
available in the container which, while common, won't always be the
case.
2023-04-13 16:08:43 +01:00

161 lines
4.0 KiB
Ruby

class Mrsk::Commands::App < Mrsk::Commands::Base
attr_reader :role
def initialize(config, role: nil)
super(config)
@role = role
end
def run
role = config.role(self.role)
docker :run,
"--detach",
"--restart unless-stopped",
"--name", container_name,
"-e", "MRSK_CONTAINER_NAME=\"#{container_name}\"",
*role.env_args,
*role.health_check_args,
*config.logging_args,
*config.volume_args,
*role.label_args,
*role.option_args,
config.absolute_image,
role.cmd
end
def start
docker :start, container_name
end
def status(version:)
pipe container_id_for_version(version), xargs(docker(:inspect, "--format", DOCKER_HEALTH_STATUS_FORMAT))
end
def stop(version: nil)
pipe \
version ? container_id_for_version(version) : current_running_container_id,
xargs(config.stop_wait_time ? docker(:stop, "-t", config.stop_wait_time) : docker(:stop))
end
def info
docker :ps, *filter_args
end
def logs(since: nil, lines: nil, grep: nil)
pipe \
current_running_container_id,
"xargs docker logs#{" --since #{since}" if since}#{" --tail #{lines}" if lines} 2>&1",
("grep '#{grep}'" if grep)
end
def follow_logs(host:, grep: nil)
run_over_ssh \
pipe(
current_running_container_id,
"xargs docker logs --timestamps --tail 10 --follow 2>&1",
(%(grep "#{grep}") if grep)
),
host: host
end
def execute_in_existing_container(*command, interactive: false)
docker :exec,
("-it" if interactive),
container_name,
*command
end
def execute_in_new_container(*command, interactive: false)
docker :run,
("-it" if interactive),
"--rm",
*config.env_args,
*config.volume_args,
config.absolute_image,
*command
end
def execute_in_existing_container_over_ssh(*command, host:)
run_over_ssh execute_in_existing_container(*command, interactive: true), host: host
end
def execute_in_new_container_over_ssh(*command, host:)
run_over_ssh execute_in_new_container(*command, interactive: true), host: host
end
def current_running_container_id
docker :ps, "--quiet", *filter_args(status: :running), "--latest"
end
def container_id_for_version(version)
container_id_for(container_name: container_name(version))
end
def current_running_version
list_versions("--latest", status: :running)
end
def list_versions(*docker_args, status: nil)
pipe \
docker(:ps, *filter_args(status: status), *docker_args, "--format", '"{{.Names}}"'),
%(grep -oE "\\-[^-]+$"), # Extract SHA from "service-role-dest-SHA"
%(cut -c 2-)
end
def list_containers
docker :container, :ls, "--all", *filter_args
end
def list_container_names
[ *list_containers, "--format", "'{{ .Names }}'" ]
end
def remove_container(version:)
pipe \
container_id_for(container_name: container_name(version)),
xargs(docker(:container, :rm))
end
def rename_container(version:, new_version:)
docker :rename, container_name(version), container_name(new_version)
end
def remove_containers
docker :container, :prune, "--force", *filter_args
end
def list_images
docker :image, :ls, config.repository
end
def remove_images
docker :image, :prune, "--all", "--force", *filter_args
end
def tag_current_as_latest
docker :tag, config.absolute_image, config.latest_image
end
private
def container_name(version = nil)
[ config.service, role, config.destination, version || config.version ].compact.join("-")
end
def filter_args(status: nil)
argumentize "--filter", filters(status: status)
end
def filters(status: nil)
[ "label=service=#{config.service}" ].tap do |filters|
filters << "label=destination=#{config.destination}" if config.destination
filters << "label=role=#{role}" if role
filters << "status=#{status}" if status
end
end
end