DuplicateContentResourceHandler to monitor resources and track how many times th…

content/browser/renderer_host/duplicate_content_resource_handler.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.
+
+#include "content/browser/renderer_host/duplicate_content_resource_handler.h"
+
+#include <set>
+
+#include "base/logging.h"
+#include "base/metrics/histogram.h"
+#include "content/browser/renderer_host/resource_request_info_impl.h"
+#include "net/base/io_buffer.h"
+#include "net/url_request/url_request.h"
+
+namespace content {
+namespace {
+
+class GlobalDuplicateRecords {
+ public:
+  static GlobalDuplicateRecords* GetInstance() {
+    static GlobalDuplicateRecords records;
+    return &records;
+  }
+
+  std::set<MH_UINT32>* content_matches() {
+    return &content_matches_;
+  }
+
+  std::set<MH_UINT32>* content_and_url_matches() {
+    return &content_and_url_matches_;
+  }
+
+ private:
+  GlobalDuplicateRecords() {}
+  ~GlobalDuplicateRecords() {}
+
+  std::set<MH_UINT32> content_matches_;
+  std::set<MH_UINT32> content_and_url_matches_;
+};
+
+}  // namespace
+
+DuplicateContentResourceHandler::DuplicateContentResourceHandler(
+    scoped_ptr<ResourceHandler> next_handler,
+    ResourceType::Type resource_type,
+    net::URLRequest* request)
+    : LayeredResourceHandler(next_handler.Pass()),
+      resource_type_(resource_type),
+      bytes_read_(0),
+      request_(request),
+      pmurhash_ph1_(0),
+      pmurhash_pcarry_(0) {
+}
+
+DuplicateContentResourceHandler::~DuplicateContentResourceHandler() {
+}
+
+bool DuplicateContentResourceHandler::
+    OnWillRead(int request_id, net::IOBuffer** buf,
+              int* buf_size, int min_size) {

[darin (slow to review), 2012/07/31 18:21:03]

nit: indentation

nit: formatting, should look like this:

  bool Foo::Bar(
      A a,
      B b,
      C c,
      D d) {
    ...
  }

+  DCHECK_EQ(-1, min_size);
+
+  if (!next_handler_->OnWillRead(request_id, buf, buf_size, min_size))
+    return false;
+  read_buffer_ = *buf;
+  return true;
+}
+
+bool DuplicateContentResourceHandler::
+    OnReadCompleted(int request_id, int bytes_read, bool* defer) {

[darin (slow to review), 2012/07/31 18:21:03]

ditto... you formatted correctly for OnResponseCompleted

+  PMurHash32_Process(&pmurhash_ph1_, &pmurhash_pcarry_,
+                      read_buffer_->data(), bytes_read);
+  bytes_read_ += bytes_read;
+  return next_handler_->OnReadCompleted(request_id, bytes_read, defer);
+}
+
+bool DuplicateContentResourceHandler::OnResponseCompleted(
+    int request_id,
+    const net::URLRequestStatus& status,
+    const std::string& security_info) {
+
+  if (status.is_success())
+    RecordContentMetrics();
+
+  return next_handler_->OnResponseCompleted(request_id, status, security_info);
+}
+
+void DuplicateContentResourceHandler::RecordContentMetrics() {
+  MH_UINT32 contents_hash = PMurHash32_Result(pmurhash_ph1_,
+                                              pmurhash_pcarry_, bytes_read_);
+
+  // Combine the contents_hash with the url, so we can test if future content
+  // identical resources have the same original url or not.
+  MH_UINT32 hashed_with_url;
+  const std::string& url_spec = request_->url().spec();
+  PMurHash32_Process(&pmurhash_ph1_, &pmurhash_pcarry_,
+                     url_spec.data(), url_spec.length());
+  hashed_with_url = PMurHash32_Result(pmurhash_ph1_, pmurhash_pcarry_,
+                                      url_spec.length() + bytes_read_);
+
+  /*DVLOG(4) << "url: " << url_spec;

[darin (slow to review), 2012/07/31 18:21:03]

nit: either uncomment this code or delete the code.

+  DVLOG(4) << "contents hash: " << contents_hash;
+  DVLOG(4) << "hash with url: " << hashed_with_url;*/
+
+  std::set<MH_UINT32>* content_matches =
+      GlobalDuplicateRecords::GetInstance()->content_matches();
+  std::set<MH_UINT32>* content_and_url_matches =
+      GlobalDuplicateRecords::GetInstance()->content_and_url_matches();
+
+  const bool did_match_contents = content_matches->count(contents_hash) > 0;
+  const bool did_match_contents_and_url =
+      content_and_url_matches->count(hashed_with_url) > 0;
+
+  UMA_HISTOGRAM_BOOLEAN("Duplicate.Hits", did_match_contents);
+  UMA_HISTOGRAM_BOOLEAN("Duplicate.HitsSameUrl", did_match_contents &&
+                         did_match_contents_and_url);
+  if (did_match_contents && !did_match_contents_and_url) {
+    content_and_url_matches->insert(hashed_with_url);
+    UMA_HISTOGRAM_CUSTOM_COUNTS("Duplicate.Size.HashHitUrlMiss", bytes_read_,
+                                 1, 0x7FFFFFFF, 50);
+    UMA_HISTOGRAM_ENUMERATION("Duplicate.ResourceType.HashHitUrlMiss",
+                               resource_type_, ResourceType::LAST_TYPE);
+  }
+  content_matches->insert(contents_hash);
+  content_and_url_matches->insert(hashed_with_url);
+
+  bytes_read_ = 0;
+  read_buffer_ = NULL;
+}
+
+}  // namespace content