The API for periodic health checks is repetitive, with a distinct
function for polling a checker to each kind of updater. It also gives
the user no control over the lifetime of the polling goroutines nor
which context is passed into the checker.
Replace the existing PeriodicXYZChecker functions with a single Poll
function which composes an Updater with a Checker. Its context parameter
is passed into the checker and also controls when the polling loop
terminates. To guard against health checks failing closed (ostensibly
healthy) when the polling loop is terminated, the updater is forcefully
updated to an error status, overriding any configured threshold.
Signed-off-by: Cory Snider <csnider@mirantis.com>
Allow health checkers to abort if the request context is canceled.
Modify the checkers to respect context cancelation and return wrapped
errors so the caller of CheckStatus() would be able to discriminate true
failed checks from checks which were aborted because the context became
done.
Signed-off-by: Cory Snider <csnider@mirantis.com>
Update docs.
Change health_test.go tests to create their own registries and register
the checks there. The tests now call CheckStatus directly instead of
polling the HTTP handler, which returns results from the default
registry.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
To ensure the ensure the web application is properly operating, we've added a
periodic health check for the storage driver. If the health check fails three
times in a row, the registry will serve 503 response status for any request
until the condition is resolved. The condition is reported in the response body
and via the /debug/health endpoint.
To ensure that all drivers will properly operate with this health check, a
function has been added to the driver testsuite.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
