Componentize renderer side of DNS prefetching.

chrome/renderer/net/renderer_net_predictor.cc

-// Copyright (c) 2012 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.
-
-// See header file for description of RendererNetPredictor class
-
-#include "chrome/renderer/net/renderer_net_predictor.h"
-
-#include <ctype.h>
-
-#include "base/bind.h"
-#include "base/logging.h"
-#include "base/message_loop/message_loop.h"
-#include "chrome/common/net/predictor_common.h"
-#include "chrome/common/render_messages.h"
-#include "chrome/renderer/net/predictor_queue.h"
-#include "content/public/renderer/render_thread.h"
-
-using content::RenderThread;
-
-// The number of hostnames submitted to Browser DNS resolver per call to
-// SubmitHostsnames() (which reads names from our queue).
-static const size_t kMAX_SUBMISSION_PER_TASK = 30;
-
-RendererNetPredictor::RendererNetPredictor()
-    : c_string_queue_(1000),
-      weak_factory_(this) {
-  Reset();
-}
-
-RendererNetPredictor::~RendererNetPredictor() {
-}
-
-void RendererNetPredictor::Reset() {
-  domain_map_.clear();
-  c_string_queue_.Clear();
-  buffer_full_discard_count_ = 0;
-  numeric_ip_discard_count_ = 0;
-  new_name_count_ = 0;
-}
-
-// Push names into queue quickly!
-void RendererNetPredictor::Resolve(const char* name, size_t length) {
-  if (!length)
-    return;  // Don't store empty strings in buffer.
-  if (is_numeric_ip(name, length))
-    return;  // Numeric IPs have no DNS lookup significance.
-
-  size_t old_size =  c_string_queue_.Size();
-  DnsQueue::PushResult result = c_string_queue_.Push(name, length);
-  if (DnsQueue::SUCCESSFUL_PUSH == result) {
-    if (1 == c_string_queue_.Size()) {
-      DCHECK_EQ(old_size, 0u);
-      if (0 != old_size)
-        return;  // Overkill safety net: Don't send too many InvokeLater's.
-      weak_factory_.InvalidateWeakPtrs();
-      RenderThread::Get()->GetMessageLoop()->PostDelayedTask(
-          FROM_HERE, base::Bind(&RendererNetPredictor::SubmitHostnames,
-                                weak_factory_.GetWeakPtr()),
-          base::TimeDelta::FromMilliseconds(10));
-    }
-    return;
-  }
-  if (DnsQueue::OVERFLOW_PUSH == result) {
-    ++buffer_full_discard_count_;
-    return;
-  }
-  DCHECK(DnsQueue::REDUNDANT_PUSH == result);
-}
-
-// Extract data from the Queue, and then send it off the the Browser process
-// to be resolved.
-void RendererNetPredictor::SubmitHostnames() {
-  // Get all names out of the C_string_queue (into our map)
-  ExtractBufferedNames();
-  // TBD: IT could be that we should only extract about as many names as we are
-  // going to send to the browser.  That would cause a "silly" page with a TON
-  // of URLs to start to overrun the DnsQueue, which will cause the names to
-  // be dropped (not stored in the queue).  By fetching ALL names, we are
-  // taking on a lot of work, which may take a long time to process... perhaps
-  // longer than the page may be visible!?!?!  If we implement a better
-  // mechanism for doing domain_map.clear() (see end of this method), then
-  // we'd automatically flush such pending work from a ridiculously link-filled
-  // page.
-
-  // Don't overload the browser DNS lookup facility, or take too long here,
-  // by only sending off kMAX_SUBMISSION_PER_TASK names to the Browser.
-  // This will help to avoid overloads when a page has a TON of links.
-  DnsPrefetchNames(kMAX_SUBMISSION_PER_TASK);
-  if (new_name_count_ > 0 || 0 < c_string_queue_.Size()) {
-    weak_factory_.InvalidateWeakPtrs();
-    RenderThread::Get()->GetMessageLoop()->PostDelayedTask(
-        FROM_HERE, base::Bind(&RendererNetPredictor::SubmitHostnames,
-                              weak_factory_.GetWeakPtr()),
-        base::TimeDelta::FromMilliseconds(10));
-  } else {
-    // TODO(JAR): Should we only clear the map when we navigate, or reload?
-    domain_map_.clear();
-  }
-}
-
-// Pull some hostnames from the queue, and add them to our map.
-void RendererNetPredictor::ExtractBufferedNames(size_t size_goal) {
-  size_t count(0);  // Number of entries to find (0 means find all).
-  if (size_goal > 0) {
-    if (size_goal <= domain_map_.size())
-      return;  // Size goal was met.
-    count = size_goal - domain_map_.size();
-  }
-
-  std::string name;
-  while (c_string_queue_.Pop(&name)) {
-    DCHECK_NE(name.size(), 0u);
-    // We don't put numeric IP names into buffer.
-    DCHECK(!is_numeric_ip(name.c_str(), name.size()));
-    DomainUseMap::iterator it;
-    it = domain_map_.find(name);
-    if (domain_map_.end() == it) {
-      domain_map_[name] = kPending;
-      ++new_name_count_;
-      if (0 == count) continue;  // Until buffer is empty.
-      if (1 == count) break;  // We found size_goal.
-      DCHECK_GT(count, 1u);
-      --count;
-    } else {
-      DCHECK(kPending == it->second || kLookupRequested == it->second);
-    }
-  }
-}
-
-void RendererNetPredictor::DnsPrefetchNames(size_t max_count) {
-  // We are on the renderer thread, and just need to send things to the browser.
-  chrome_common_net::NameList names;
-  for (DomainUseMap::iterator it = domain_map_.begin();
-    it != domain_map_.end();
-    ++it) {
-    if (0 == (it->second & kLookupRequested)) {
-      it->second |= kLookupRequested;
-      names.push_back(it->first);
-      if (0 == max_count) continue;  // Get all, independent of count.
-      if (1 == max_count) break;
-      --max_count;
-      DCHECK_GE(max_count, 1u);
-    }
-  }
-  DCHECK_GE(new_name_count_, names.size());
-  new_name_count_ -= names.size();
-
-  RenderThread::Get()->Send(new ChromeViewHostMsg_DnsPrefetch(names));
-}
-
-// is_numeric_ip() checks to see if all characters in name are either numeric,
-// or dots.  Such a name will not actually be passed to DNS, as it is an IP
-// address.
-bool RendererNetPredictor::is_numeric_ip(const char* name, size_t length) {
-  // Scan for a character outside our lookup list.
-  while (length-- > 0) {
-    if (!isdigit(*name) && '.' != *name)
-      return false;
-    ++name;
-  }
-  return true;
-}