The two methods nextScheduledTimeDuration and getNextScheduleTime have a
lot of similarities, so this commit squashes the common parts together
along with getMostRecentScheduleTime to avoid code duplication.
The unit tests were broken with MinimizeIPTablesRestore enabled
because syncProxyRules() assumed that needFullSync would be set on the
first (post-setInitialized()) run, but the unit tests didn't ensure
that.
(In fact, there was a race condition in the real Proxier case as well;
theoretically syncProxyRules() could be run by the
BoundedFrequencyRunner after OnServiceSynced() called setInitialized()
but before it called forceSyncProxyRules(), thus causing the first
real sync to try to do a partial sync and fail. This is now fixed as
well.)
ContextForChannel uses a goroutine to transform a channel close to
a context cancel. However, this exposes a synchronization issue if
we want to unify the underlying implementation between contextless
and with context - a ConditionFunc that closes the channel today
expects the behavior that no subsequent conditions will be invoked
(we have a test in wait_test.go TestUntilReturnsImmediately that
verifies this expectation). We can't unify the implementation
without ensuring this property holds.
To do that this commit changes from the goroutine propagation to
implementing context.Context and using stopCh as the Done(). We
then implement Err() by returning context.Canceled and stub the
other methods. Since our context cannot be explicitly cancelled
by users, we cease to return the cancelFn and callers that need
that behavior must wrap the context as normal.
This should be invisible to clients - they would already observe
the same behavior from the context, and the existing error
behavior of Poll* is preserved (which ignores ctx.Err()).
As a side effect, one less goroutine is created making it more
efficient.
A full string comparison might fail when the underlying libraries change how
they format the help text. A regex match is less strict, but still makes some
assumptions about the implementation.
These methods are unused within the Kubernetes codebase and will be
replaced with a more general method that unifies Wait, Poll*, and
ExponentialBackoff within this package. A zero duration interval
passed to any of the other methods will provide equivalent function.
