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Deliver cached stats reports asynchronously.

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This has the following benefits:
* Stats reports are always delivered asynchronously. This means the API
  client doesn't need to worry about *possibly* getting a synchronous
  callback depending on when the last report was generated.
* Stats callbacks will always be invoked in the same order that the
  GetStats calls were made, even in cases where a callback recursively
  calls GetStats again.

Bug: webrtc:8973
Change-Id: I94ca4b5dc5c21a8f2df42adfcddf357f40a32025
Reviewed-on: https://webrtc-review.googlesource.com/60473
Commit-Queue: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22348}
This commit is contained in:
Taylor Brandstetter
2018-03-08 09:53:47 -08:00
committed by Commit Bot
parent 6328d7cbbc
commit 25e022fd5c
3 changed files with 32 additions and 20 deletions
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34
pc/rtcstatscollector.cc
View File

@ -648,8 +648,16 @@ void RTCStatsCollector::GetStatsReport(
int64_t cache_now_us = rtc::TimeMicros();
if (cached_report_ &&
cache_now_us - cache_timestamp_us_ <= cache_lifetime_us_) {
// We have a fresh cached report to deliver.
DeliverCachedReport();
// We have a fresh cached report to deliver. Deliver asynchronously, since
// the caller may not be expecting a synchronous callback, and it avoids
// reentrancy problems.
std::vector<rtc::scoped_refptr<RTCStatsCollectorCallback>> callbacks;
callbacks.swap(callbacks_);
invoker_.AsyncInvoke<void>(
RTC_FROM_HERE, signaling_thread_,
rtc::Bind(&RTCStatsCollector::DeliverCachedReport, this, cached_report_,
std::move(callbacks)));
callbacks_.clear();
} else if (!num_pending_partial_reports_) {
// Only start gathering stats if we're not already gathering stats. In the
// case of already gathering stats, |callback_| will be invoked when there
@ -772,23 +780,25 @@ void RTCStatsCollector::AddPartialResults_s(
// select the "webrtc_stats" category when recording traces.
TRACE_EVENT_INSTANT1("webrtc_stats", "webrtc_stats", "report",
cached_report_->ToJson());
DeliverCachedReport();
// Swap the list of callbacks, in case one of them recursively calls
// GetStatsReport again and modifies the callback list.
std::vector<rtc::scoped_refptr<RTCStatsCollectorCallback>> callbacks;
callbacks.swap(callbacks_);
DeliverCachedReport(cached_report_, std::move(callbacks));
}
}
void RTCStatsCollector::DeliverCachedReport() {
void RTCStatsCollector::DeliverCachedReport(
rtc::scoped_refptr<const RTCStatsReport> cached_report,
std::vector<rtc::scoped_refptr<RTCStatsCollectorCallback>> callbacks) {
RTC_DCHECK(signaling_thread_->IsCurrent());
RTC_DCHECK(!callbacks_.empty());
RTC_DCHECK(cached_report_);
// Swap the list of callbacks, in case one of them recursively calls
// GetStatsReport again and modifies the callback list.
std::vector<rtc::scoped_refptr<RTCStatsCollectorCallback>> callbacks;
callbacks.swap(callbacks_);
RTC_DCHECK(!callbacks.empty());
RTC_DCHECK(cached_report);
for (const rtc::scoped_refptr<RTCStatsCollectorCallback>& callback :
callbacks) {
callback->OnStatsDelivered(cached_report_);
callback->OnStatsDelivered(cached_report);
}
}