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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "chrome/browser/predictors/resource_prefetcher.h"
#include <iterator>
#include <utility>
#include "base/trace_event/trace_event.h"
#include "content/public/browser/browser_thread.h"
#include "net/base/io_buffer.h"
#include "net/base/load_flags.h"
#include "net/base/request_priority.h"
#include "net/url_request/url_request_context.h"
#include "url/origin.h"
namespace {
// The size of the buffer used to read the resource.
static const size_t kResourceBufferSizeBytes = 50000;
} // namespace
namespace predictors {
ResourcePrefetcher::ResourcePrefetcher(
Delegate* delegate,
const ResourcePrefetchPredictorConfig& config,
const GURL& main_frame_url,
const std::vector<GURL>& urls)
: state_(INITIALIZED),
delegate_(delegate),
config_(config),
main_frame_url_(main_frame_url) {
DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
std::copy(urls.begin(), urls.end(), std::back_inserter(request_queue_));
}
ResourcePrefetcher::~ResourcePrefetcher() {}
void ResourcePrefetcher::Start() {
TRACE_EVENT_ASYNC_BEGIN0("browser", "ResourcePrefetcher::Prefetch", this);
DCHECK(thread_checker_.CalledOnValidThread());
CHECK_EQ(state_, INITIALIZED);
state_ = RUNNING;
TryToLaunchPrefetchRequests();
}
void ResourcePrefetcher::Stop() {
TRACE_EVENT_ASYNC_END0("browser", "ResourcePrefetcher::Prefetch", this);
DCHECK(thread_checker_.CalledOnValidThread());
if (state_ == FINISHED)
return;
state_ = STOPPED;
}
void ResourcePrefetcher::TryToLaunchPrefetchRequests() {
CHECK(state_ == RUNNING || state_ == STOPPED);
// Try to launch new requests if the state is RUNNING.
if (state_ == RUNNING) {
bool request_available = true;
// Loop through the requests while we are under the
// max_prefetches_inflight_per_host_per_navigation limit, looking for a URL
// for which the max_prefetches_inflight_per_host_per_navigation limit has
// not been reached. Try to launch as many requests as possible.
while ((inflight_requests_.size() <
config_.max_prefetches_inflight_per_navigation) &&
request_available) {
auto request_it = request_queue_.begin();
for (; request_it != request_queue_.end(); ++request_it) {
const std::string& host = request_it->host();
std::map<std::string, size_t>::iterator host_it =
host_inflight_counts_.find(host);
if (host_it == host_inflight_counts_.end() ||
host_it->second <
config_.max_prefetches_inflight_per_host_per_navigation)
break;
}
request_available = request_it != request_queue_.end();
if (request_available) {
SendRequest(*request_it);
request_queue_.erase(request_it);
}
}
}
// If the inflight_requests_ is empty, we can't launch any more. Finish.
if (inflight_requests_.empty()) {
CHECK(host_inflight_counts_.empty());
CHECK(request_queue_.empty() || state_ == STOPPED);
state_ = FINISHED;
delegate_->ResourcePrefetcherFinished(this);
}
}
void ResourcePrefetcher::SendRequest(const GURL& url) {
std::unique_ptr<net::URLRequest> url_request =
delegate_->GetURLRequestContext()->CreateRequest(url, net::LOW, this);
host_inflight_counts_[url.host()] += 1;
url_request->set_method("GET");
url_request->set_first_party_for_cookies(main_frame_url_);
url_request->set_initiator(url::Origin(main_frame_url_));
url_request->SetReferrer(main_frame_url_.spec());
url_request->SetLoadFlags(url_request->load_flags() | net::LOAD_PREFETCH);
StartURLRequest(url_request.get());
inflight_requests_.insert(
std::make_pair(url_request.get(), std::move(url_request)));
}
void ResourcePrefetcher::StartURLRequest(net::URLRequest* request) {
request->Start();
}
void ResourcePrefetcher::FinishRequest(net::URLRequest* request) {
auto request_it = inflight_requests_.find(request);
CHECK(request_it != inflight_requests_.end());
const std::string host = request->original_url().host();
std::map<std::string, size_t>::iterator host_it = host_inflight_counts_.find(
host);
CHECK_GT(host_it->second, 0U);
host_it->second -= 1;
if (host_it->second == 0)
host_inflight_counts_.erase(host);
inflight_requests_.erase(request_it);
TryToLaunchPrefetchRequests();
}
void ResourcePrefetcher::ReadFullResponse(net::URLRequest* request) {
int bytes_read = 0;
do {
scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(
kResourceBufferSizeBytes));
bytes_read = request->Read(buffer.get(), kResourceBufferSizeBytes);
if (bytes_read == net::ERR_IO_PENDING) {
return;
} else if (bytes_read <= 0) {
FinishRequest(request);
return;
}
} while (bytes_read > 0);
}
void ResourcePrefetcher::OnReceivedRedirect(
net::URLRequest* request,
const net::RedirectInfo& redirect_info,
bool* defer_redirect) {
FinishRequest(request);
}
void ResourcePrefetcher::OnAuthRequired(net::URLRequest* request,
net::AuthChallengeInfo* auth_info) {
FinishRequest(request);
}
void ResourcePrefetcher::OnCertificateRequested(
net::URLRequest* request,
net::SSLCertRequestInfo* cert_request_info) {
FinishRequest(request);
}
void ResourcePrefetcher::OnSSLCertificateError(net::URLRequest* request,
const net::SSLInfo& ssl_info,
bool fatal) {
FinishRequest(request);
}
void ResourcePrefetcher::OnResponseStarted(net::URLRequest* request,
int net_error) {
DCHECK_NE(net::ERR_IO_PENDING, net_error);
if (net_error != net::OK) {
FinishRequest(request);
return;
}
// TODO(shishir): Do not read cached entries, or ones that are not cacheable.
ReadFullResponse(request);
}
void ResourcePrefetcher::OnReadCompleted(net::URLRequest* request,
int bytes_read) {
DCHECK_NE(net::ERR_IO_PENDING, bytes_read);
if (bytes_read <= 0) {
FinishRequest(request);
return;
}
if (bytes_read > 0)
ReadFullResponse(request);
}
} // namespace predictors
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