src/chrome/browser/metrics/variations/variations_http_header_provider.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/browser/metrics/variations/variations_http_header_provider.h"
   6
   7 #include <vector>
   8
   9 #include "base/base64.h"
  10 #include "base/memory/singleton.h"
  11 #include "base/metrics/histogram.h"
  12 #include "base/strings/string_number_conversions.h"
  13 #include "base/strings/string_split.h"
  14 #include "base/strings/string_util.h"
  15 #include "chrome/browser/google/google_util.h"
  16 #include "chrome/common/metrics/proto/chrome_experiments.pb.h"
  17 #include "net/base/registry_controlled_domains/registry_controlled_domain.h"
  18 #include "net/http/http_request_headers.h"
  19 #include "url/gurl.h"
  20
  21 namespace chrome_variations {
  22
  23 VariationsHttpHeaderProvider* VariationsHttpHeaderProvider::GetInstance() {
  24   return Singleton<VariationsHttpHeaderProvider>::get();
  25 }
  26
  27 void VariationsHttpHeaderProvider::AppendHeaders(
  28     const GURL& url,
  29     bool incognito,
  30     bool uma_enabled,
  31     net::HttpRequestHeaders* headers) {
  32   // Note the criteria for attaching Chrome experiment headers:
  33   // 1. We only transmit to *.google.<TLD> or *.youtube.<TLD> domains.
  34   // 2. Only transmit for non-Incognito profiles.
  35   // 3. For the X-Chrome-UMA-Enabled bit, only set it if UMA is in fact enabled
  36   //    for this install of Chrome.
  37   // 4. For the X-Client-Data header, only include non-empty variation IDs.
  38   if (incognito || !ShouldAppendHeaders(url))
  39     return;
  40
  41   if (uma_enabled)
  42     headers->SetHeaderIfMissing("X-Chrome-UMA-Enabled", "1");
  43
  44   // Lazily initialize the header, if not already done, before attempting to
  45   // transmit it.
  46   InitVariationIDsCacheIfNeeded();
  47
  48   std::string variation_ids_header_copy;
  49   {
  50     base::AutoLock scoped_lock(lock_);
  51     variation_ids_header_copy = variation_ids_header_;
  52   }
  53
  54   if (!variation_ids_header_copy.empty()) {
  55     // Note that prior to M33 this header was named X-Chrome-Variations.
  56     headers->SetHeaderIfMissing("X-Client-Data",
  57                                 variation_ids_header_copy);
  58   }
  59 }
  60
  61 bool VariationsHttpHeaderProvider::SetDefaultVariationIds(
  62     const std::string& variation_ids) {
  63   default_variation_ids_set_.clear();
  64   std::vector<std::string> entries;
  65   base::SplitString(variation_ids, ',', &entries);
  66   for (std::vector<std::string>::const_iterator it = entries.begin();
  67        it != entries.end(); ++it) {
  68     int variation_id = 0;
  69     if (!base::StringToInt(*it, &variation_id)) {
  70       default_variation_ids_set_.clear();
  71       return false;
  72     }
  73     default_variation_ids_set_.insert(variation_id);
  74   }
  75   return true;
  76 }
  77
  78 VariationsHttpHeaderProvider::VariationsHttpHeaderProvider()
  79     : variation_ids_cache_initialized_(false) {
  80 }
  81
  82 VariationsHttpHeaderProvider::~VariationsHttpHeaderProvider() {
  83 }
  84
  85 void VariationsHttpHeaderProvider::OnFieldTrialGroupFinalized(
  86     const std::string& trial_name,
  87     const std::string& group_name) {
  88   VariationID new_id =
  89       GetGoogleVariationID(GOOGLE_WEB_PROPERTIES, trial_name, group_name);
  90   if (new_id == EMPTY_ID)
  91     return;
  92
  93   base::AutoLock scoped_lock(lock_);
  94   variation_ids_set_.insert(new_id);
  95   UpdateVariationIDsHeaderValue();
  96 }
  97
  98 void VariationsHttpHeaderProvider::InitVariationIDsCacheIfNeeded() {
  99   base::AutoLock scoped_lock(lock_);
 100   if (variation_ids_cache_initialized_)
 101     return;
 102
 103   // Register for additional cache updates. This is done first to avoid a race
 104   // that could cause registered FieldTrials to be missed.
 105   DCHECK(base::MessageLoop::current());
 106   base::FieldTrialList::AddObserver(this);
 107
 108   base::TimeTicks before_time = base::TimeTicks::Now();
 109
 110   base::FieldTrial::ActiveGroups initial_groups;
 111   base::FieldTrialList::GetActiveFieldTrialGroups(&initial_groups);
 112   for (base::FieldTrial::ActiveGroups::const_iterator it =
 113            initial_groups.begin();
 114        it != initial_groups.end(); ++it) {
 115     const VariationID id =
 116         GetGoogleVariationID(GOOGLE_WEB_PROPERTIES, it->trial_name,
 117                              it->group_name);
 118     if (id != EMPTY_ID)
 119       variation_ids_set_.insert(id);
 120   }
 121   UpdateVariationIDsHeaderValue();
 122
 123   UMA_HISTOGRAM_CUSTOM_COUNTS(
 124       "Variations.HeaderConstructionTime",
 125       (base::TimeTicks::Now() - before_time).InMicroseconds(),
 126       0,
 127       base::TimeDelta::FromSeconds(1).InMicroseconds(),
 128       50);
 129
 130   variation_ids_cache_initialized_ = true;
 131 }
 132
 133 void VariationsHttpHeaderProvider::UpdateVariationIDsHeaderValue() {
 134   lock_.AssertAcquired();
 135
 136   // The header value is a serialized protobuffer of Variation IDs which is
 137   // base64 encoded before transmitting as a string.
 138   variation_ids_header_.clear();
 139
 140   if (variation_ids_set_.empty() && default_variation_ids_set_.empty())
 141     return;
 142
 143   // This is the bottleneck for the creation of the header, so validate the size
 144   // here. Force a hard maximum on the ID count in case the Variations server
 145   // returns too many IDs and DOSs receiving servers with large requests.
 146   DCHECK_LE(variation_ids_set_.size(), 10U);
 147   if (variation_ids_set_.size() > 20)
 148     return;
 149
 150   // Merge the two sets of experiment ids.
 151   std::set<VariationID> all_variation_ids_set = default_variation_ids_set_;
 152   for (std::set<VariationID>::const_iterator it = variation_ids_set_.begin();
 153        it != variation_ids_set_.end(); ++it) {
 154     all_variation_ids_set.insert(*it);
 155   }
 156   metrics::ChromeVariations proto;
 157   for (std::set<VariationID>::const_iterator it = all_variation_ids_set.begin();
 158        it != all_variation_ids_set.end(); ++it) {
 159     proto.add_variation_id(*it);
 160   }
 161
 162   std::string serialized;
 163   proto.SerializeToString(&serialized);
 164
 165   std::string hashed;
 166   base::Base64Encode(serialized, &hashed);
 167   // If successful, swap the header value with the new one.
 168   // Note that the list of IDs and the header could be temporarily out of sync
 169   // if IDs are added as the header is recreated. The receiving servers are OK
 170   // with such discrepancies.
 171   variation_ids_header_ = hashed;
 172 }
 173
 174 // static
 175 bool VariationsHttpHeaderProvider::ShouldAppendHeaders(const GURL& url) {
 176   if (google_util::IsGoogleDomainUrl(url, google_util::ALLOW_SUBDOMAIN,
 177                                      google_util::ALLOW_NON_STANDARD_PORTS)) {
 178     return true;
 179   }
 180
 181   // The below mirrors logic in IsGoogleDomainUrl(), but for youtube.<TLD>.
 182   if (!url.is_valid() || !url.SchemeIsHTTPOrHTTPS())
 183     return false;
 184
 185   const std::string host = url.host();
 186   const size_t tld_length = net::registry_controlled_domains::GetRegistryLength(
 187       host,
 188       net::registry_controlled_domains::EXCLUDE_UNKNOWN_REGISTRIES,
 189       net::registry_controlled_domains::EXCLUDE_PRIVATE_REGISTRIES);
 190   if ((tld_length == 0) || (tld_length == std::string::npos))
 191     return false;
 192
 193   const std::string host_minus_tld(host, 0, host.length() - tld_length);
 194   return LowerCaseEqualsASCII(host_minus_tld, "youtube.") ||
 195       EndsWith(host_minus_tld, ".youtube.", false);
 196 }
 197
 198 }  // namespace chrome_variations