Envoy: quiche: add support for QuicClock::ApproximateNow

[danzh2010]

QuicClock::ApproximateNow() provides a cheaper way to get current time than calling std::steady_clock::now(). It returns a slightly lagged timestamp which is usually within acceptable range. But currently EnvoyQuicClock implements it in the same way as Now() which does call std::steady_clock::now().

A typically implementation is to store a timestamp in each event loop and return that timestamp for ApproximateNow(). In Envoy LibeventScheduler::prepare_time_|check_time_ can serve this purpose. Since DispatcherImpl owns libeventScheduler, we can add an interface Dispatcher::getSchedulerPrepareTime() to return LibeventScheduler::prepare_time_. And instead of referencing TimeSystem in QuicClock, we can change it to reference a Dispatcher which also provides TimeSource interface.

[stale[bot]]

This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or other activity occurs. Thank you for your contributions.

[stale[bot]]

This issue has been automatically closed because it has not had activity in the last 37 days. If this issue is still valid, please ping a maintainer and ask them to label it as "help wanted". Thank you for your contributions.

[danzh2010]

Please reopen this issue

[danzh2010]

/assign @bencebeky

[repokitteh[bot]]

@bencebeky cannot be assigned to this issue.

:cat:

Caused by: a https://github.com/envoyproxy/envoy/issues/7177#issuecomment-534642666 was created by @danzh2010.

see: more, trace.

[danzh2010]

/assign @bencebeky

[repokitteh[bot]]

@bencebeky cannot be assigned to this issue.

:cat:

Caused by: a https://github.com/envoyproxy/envoy/issues/7177#issuecomment-534643045 was created by @danzh2010.

see: more, trace.

[danzh2010]

@mattklein123 It seems that I don't have permission to assign issue. How to get the permission?

[mattklein123]

They need to be added to the org. I will send an invite.

[bencebeky]

/assign @bencebeky