void DefaultFileSource::Impl::update(DefaultFileRequest& request) {
if (request.getResponse()) {
// We've at least obtained a cache value, potentially we also got a final response.
// The observers have been notified already; send what we have to the new one as well.
// Before returning the existing response, make sure that it is still fresh, or update the
// `stale` flag.
request.checkResponseFreshness();
if (request.getResponse()->stale && !request.realRequest) {
// We've returned a stale response; now make sure the requester also gets a fresh
// response eventually. It's possible that there's already a request in progress.
// Note that this will also trigger updates to all other existing listeners.
// Since we already have data, we're going to verify
startRealRequest(request);
} else {
// The response is still fresh (or there's already a request for refreshing the resource
// in progress), so there's nothing we need to do.
}
} else if (!request.cacheRequest && !request.realRequest) {
// There is no request in progress, and we don't have a response yet. This means we'll have
// to start the request ourselves.
if (cache) {
startCacheRequest(request);
} else {
startRealRequest(request);
}
} else {
// There is a request in progress. We just have to wait.
}
}
void DefaultFileSource::Impl::networkIsReachableAgain() {
for (auto& req : pending) {
auto& request = req.second;
auto& response = request.getResponse();
if (!request.realRequest && response && response->error && response->error->reason == Response::Error::Reason::Connection) {
// We need all requests to fail at least once before we are going to start retrying
// them, and we only immediately restart request that failed due to connection issues.
startRealRequest(request);
}
}
}
void OnlineFileSource::Impl::reschedule(OnlineFileRequestImpl& request) {
if (request.realRequest) {
// There's already a request in progress; don't start another one.
return;
}
const Seconds timeout = request.getRetryTimeout();
if (timeout == Seconds::zero()) {
update(request);
} else if (timeout > Seconds::zero()) {
request.realRequestTimer.start(timeout, Duration::zero(), [this, &request] {
assert(!request.realRequest);
startRealRequest(request);
});
}
}
void OnlineFileSource::Impl::startCacheRequest(OnlineFileRequestImpl& request) {
// Check the cache for existing data so that we can potentially
// revalidate the information without having to redownload everything.
request.cacheRequest =
cache->get(request.resource, [this, &request](std::shared_ptr<Response> response) {
request.cacheRequest = nullptr;
if (response) {
response->stale = response->isExpired();
request.setResponse(response);
}
if (!response || response->stale) {
// No response or stale cache. Run the real request.
startRealRequest(request);
}
reschedule(request);
});
}
void DefaultFileSource::Impl::reschedule(DefaultFileRequest& request) {
if (request.realRequest) {
// There's already a request in progress; don't start another one.
return;
}
const auto timeout = request.getRetryTimeout();
if (timeout == 0) {
update(request);
} else if (timeout > 0) {
if (!request.timerRequest) {
request.timerRequest = std::make_unique<uv::timer>(util::RunLoop::getLoop());
}
// timeout is in seconds, but the timer takes milliseconds.
request.timerRequest->start(1000 * timeout, 0, [this, &request] {
assert(!request.realRequest);
startRealRequest(request);
});
}
}
void DefaultFileSource::Impl::startCacheRequest(DefaultFileRequest& request) {
// Check the cache for existing data so that we can potentially
// revalidate the information without having to redownload everything.
request.cacheRequest =
cache->get(request.resource, [this, &request](std::shared_ptr<Response> response) {
request.cacheRequest = nullptr;
if (response) {
response->stale = response->isExpired();
request.setResponse(response);
}
if (!response || response->stale) {
// No response or stale cache. Run the real request.
startRealRequest(request);
}
// Notify in all cases; requestors can decide whether they want to use stale responses.
request.notify();
reschedule(request);
});
}