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Move health checks into Docker

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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.
This commit is contained in:
Kevin McConnell
2023-04-07 11:14:51 +01:00
parent bc8875e020
commit df202d6ef4
13 changed files with 186 additions and 115 deletions
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16
test/configuration/role_test.rb
View File

@@ -42,7 +42,7 @@ class ConfigurationRoleTest < ActiveSupport::TestCase
end
test "special label args for web" do
assert_equal [ "--label", "service=\"app\"", "--label", "role=\"web\"", "--label", "traefik.http.routers.app-web.rule=\"PathPrefix(\\`/\\`)\"", "--label", "traefik.http.services.app-web.loadbalancer.healthcheck.path=\"/up\"", "--label", "traefik.http.services.app-web.loadbalancer.healthcheck.interval=\"1s\"", "--label", "traefik.http.middlewares.app-web-retry.retry.attempts=\"5\"", "--label", "traefik.http.middlewares.app-web-retry.retry.initialinterval=\"500ms\"", "--label", "traefik.http.routers.app-web.middlewares=\"app-web-retry@docker\"" ], @config.role(:web).label_args
assert_equal [ "--label", "service=\"app\"", "--label", "role=\"web\"", "--label", "traefik.http.routers.app-web.rule=\"PathPrefix(\\`/\\`)\"", "--label", "traefik.http.middlewares.app-web-retry.retry.attempts=\"5\"", "--label", "traefik.http.middlewares.app-web-retry.retry.initialinterval=\"500ms\"", "--label", "traefik.http.routers.app-web.middlewares=\"app-web-retry@docker\"" ], @config.role(:web).label_args
end
test "custom labels" do
@@ -57,8 +57,8 @@ class ConfigurationRoleTest < ActiveSupport::TestCase
end
test "overwriting default traefik label" do
@deploy[:labels] = { "traefik.http.routers.app.rule" => "\"Host(\\`example.com\\`) || (Host(\\`example.org\\`) && Path(\\`/traefik\\`))\"" }
assert_equal "\"Host(\\`example.com\\`) || (Host(\\`example.org\\`) && Path(\\`/traefik\\`))\"", @config.role(:web).labels["traefik.http.routers.app.rule"]
@deploy[:labels] = { "traefik.http.routers.app-web.rule" => "\"Host(\\`example.com\\`) || (Host(\\`example.org\\`) && Path(\\`/traefik\\`))\"" }
assert_equal "\"Host(\\`example.com\\`) || (Host(\\`example.org\\`) && Path(\\`/traefik\\`))\"", @config.role(:web).labels["traefik.http.routers.app-web.rule"]
end
test "default traefik label on non-web role" do
@@ -66,15 +66,7 @@ class ConfigurationRoleTest < ActiveSupport::TestCase
c[:servers]["beta"] = { "traefik" => "true", "hosts" => [ "1.1.1.5" ] }
})
assert_equal [ "--label", "service=\"app\"", "--label", "role=\"beta\"", "--label", "traefik.http.routers.app-beta.rule=\"PathPrefix(\\`/\\`)\"", "--label", "traefik.http.services.app-beta.loadbalancer.healthcheck.path=\"/up\"", "--label", "traefik.http.services.app-beta.loadbalancer.healthcheck.interval=\"1s\"", "--label", "traefik.http.middlewares.app-beta-retry.retry.attempts=\"5\"", "--label", "traefik.http.middlewares.app-beta-retry.retry.initialinterval=\"500ms\"", "--label", "traefik.http.routers.app-beta.middlewares=\"app-beta-retry@docker\"" ], config.role(:beta).label_args
end
test "default traefik label for non-web role with destination" do
config = Mrsk::Configuration.new(@deploy_with_roles.tap { |c|
c[:servers]["beta"] = { "traefik" => "true", "hosts" => [ "1.1.1.5" ] }
}, destination: "staging")
assert_equal [ "--label", "service=\"app\"", "--label", "role=\"beta\"", "--label", "destination=\"staging\"", "--label", "traefik.http.routers.app-beta-staging.rule=\"PathPrefix(\\`/\\`)\"", "--label", "traefik.http.services.app-beta-staging.loadbalancer.healthcheck.path=\"/up\"", "--label", "traefik.http.services.app-beta-staging.loadbalancer.healthcheck.interval=\"1s\"", "--label", "traefik.http.middlewares.app-beta-staging-retry.retry.attempts=\"5\"", "--label", "traefik.http.middlewares.app-beta-staging-retry.retry.initialinterval=\"500ms\"", "--label", "traefik.http.routers.app-beta-staging.middlewares=\"app-beta-staging-retry@docker\"" ], config.role(:beta).label_args
assert_equal [ "--label", "service=\"app\"", "--label", "role=\"beta\"", "--label", "traefik.http.routers.app-beta.rule=\"PathPrefix(\\`/\\`)\"", "--label", "traefik.http.middlewares.app-beta-retry.retry.attempts=\"5\"", "--label", "traefik.http.middlewares.app-beta-retry.retry.initialinterval=\"500ms\"", "--label", "traefik.http.routers.app-beta.middlewares=\"app-beta-retry@docker\"" ], config.role(:beta).label_args
end
test "env overwritten by role" do