df202d6ef4
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.
54 lines
1.2 KiB
Ruby
54 lines
1.2 KiB
Ruby
class Mrsk::Commands::Healthcheck < Mrsk::Commands::Base
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EXPOSED_PORT = 3999
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def run
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web = config.role(:web)
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docker :run,
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"--detach",
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"--name", container_name_with_version,
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"--publish", "#{EXPOSED_PORT}:#{config.healthcheck["port"]}",
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"--label", "service=#{container_name}",
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"-e", "MRSK_CONTAINER_NAME=\"#{container_name}\"",
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*web.env_args,
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*web.health_check_args,
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*config.volume_args,
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*web.option_args,
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config.absolute_image,
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web.cmd
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end
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def status
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pipe container_id, xargs(docker(:inspect, "--format", DOCKER_HEALTH_STATUS_FORMAT))
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end
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def logs
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pipe container_id, xargs(docker(:logs, "--tail", 50, "2>&1"))
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end
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def stop
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pipe container_id, xargs(docker(:stop))
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end
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def remove
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pipe container_id, xargs(docker(:container, :rm))
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end
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private
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def container_name
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[ "healthcheck", config.service, config.destination ].compact.join("-")
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end
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def container_name_with_version
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"#{container_name}-#{config.version}"
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end
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def container_id
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container_id_for(container_name: container_name_with_version)
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end
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def health_url
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"http://localhost:#{EXPOSED_PORT}#{config.healthcheck["path"]}"
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end
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end
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