extensions/browser/quota_service.cc

   1 // Copyright 2013 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 "extensions/browser/quota_service.h"
   6
   7 #include "base/message_loop/message_loop.h"
   8 #include "base/stl_util.h"
   9 #include "extensions/browser/extension_function.h"
  10 #include "extensions/common/error_utils.h"
  11
  12 namespace {
  13
  14 // If the browser stays open long enough, we reset state once a day.
  15 // Whatever this value is, it should be an order of magnitude longer than
  16 // the longest interval in any of the QuotaLimitHeuristics in use.
  17 const int kPurgeIntervalInDays = 1;
  18
  19 const char kOverQuotaError[] = "This request exceeds the * quota.";
  20
  21 }  // namespace
  22
  23 namespace extensions {
  24
  25 QuotaService::QuotaService() {
  26   if (base::MessageLoop::current() != NULL) {  // Null in unit tests.
  27     purge_timer_.Start(FROM_HERE,
  28                        base::TimeDelta::FromDays(kPurgeIntervalInDays),
  29                        this,
  30                        &QuotaService::Purge);
  31   }
  32 }
  33
  34 QuotaService::~QuotaService() {
  35   DCHECK(CalledOnValidThread());
  36   purge_timer_.Stop();
  37   Purge();
  38 }
  39
  40 std::string QuotaService::Assess(const std::string& extension_id,
  41                                  ExtensionFunction* function,
  42                                  const base::ListValue* args,
  43                                  const base::TimeTicks& event_time) {
  44   DCHECK(CalledOnValidThread());
  45
  46   if (function->ShouldSkipQuotaLimiting())
  47     return std::string();
  48
  49   // Lookup function list for extension.
  50   FunctionHeuristicsMap& functions = function_heuristics_[extension_id];
  51
  52   // Lookup heuristics for function, create if necessary.
  53   QuotaLimitHeuristics& heuristics = functions[function->name()];
  54   if (heuristics.empty())
  55     function->GetQuotaLimitHeuristics(&heuristics);
  56
  57   if (heuristics.empty())
  58     return std::string();  // No heuristic implies no limit.
  59
  60   ViolationErrorMap::iterator violation_error =
  61       violation_errors_.find(extension_id);
  62   if (violation_error != violation_errors_.end())
  63     return violation_error->second;  // Repeat offender.
  64
  65   QuotaLimitHeuristic* failed_heuristic = NULL;
  66   for (QuotaLimitHeuristics::iterator heuristic = heuristics.begin();
  67        heuristic != heuristics.end();
  68        ++heuristic) {
  69     // Apply heuristic to each item (bucket).
  70     if (!(*heuristic)->ApplyToArgs(args, event_time)) {
  71       failed_heuristic = *heuristic;
  72       break;
  73     }
  74   }
  75
  76   if (!failed_heuristic)
  77     return std::string();
  78
  79   std::string error = failed_heuristic->GetError();
  80   DCHECK_GT(error.length(), 0u);
  81
  82   PurgeFunctionHeuristicsMap(&functions);
  83   function_heuristics_.erase(extension_id);
  84   violation_errors_[extension_id] = error;
  85   return error;
  86 }
  87
  88 void QuotaService::PurgeFunctionHeuristicsMap(FunctionHeuristicsMap* map) {
  89   FunctionHeuristicsMap::iterator heuristics = map->begin();
  90   while (heuristics != map->end()) {
  91     STLDeleteElements(&heuristics->second);
  92     map->erase(heuristics++);
  93   }
  94 }
  95
  96 void QuotaService::Purge() {
  97   DCHECK(CalledOnValidThread());
  98   std::map<std::string, FunctionHeuristicsMap>::iterator it =
  99       function_heuristics_.begin();
 100   for (; it != function_heuristics_.end(); function_heuristics_.erase(it++))
 101     PurgeFunctionHeuristicsMap(&it->second);
 102 }
 103
 104 void QuotaLimitHeuristic::Bucket::Reset(const Config& config,
 105                                         const base::TimeTicks& start) {
 106   num_tokens_ = config.refill_token_count;
 107   expiration_ = start + config.refill_interval;
 108 }
 109
 110 void QuotaLimitHeuristic::SingletonBucketMapper::GetBucketsForArgs(
 111     const base::ListValue* args,
 112     BucketList* buckets) {
 113   buckets->push_back(&bucket_);
 114 }
 115
 116 QuotaLimitHeuristic::QuotaLimitHeuristic(const Config& config,
 117                                          BucketMapper* map,
 118                                          const std::string& name)
 119     : config_(config), bucket_mapper_(map), name_(name) {}
 120
 121 QuotaLimitHeuristic::~QuotaLimitHeuristic() {}
 122
 123 bool QuotaLimitHeuristic::ApplyToArgs(const base::ListValue* args,
 124                                       const base::TimeTicks& event_time) {
 125   BucketList buckets;
 126   bucket_mapper_->GetBucketsForArgs(args, &buckets);
 127   for (BucketList::iterator i = buckets.begin(); i != buckets.end(); ++i) {
 128     if ((*i)->expiration().is_null())  // A brand new bucket.
 129       (*i)->Reset(config_, event_time);
 130     if (!Apply(*i, event_time))
 131       return false;  // It only takes one to spoil it for everyone.
 132   }
 133   return true;
 134 }
 135
 136 std::string QuotaLimitHeuristic::GetError() const {
 137   return extensions::ErrorUtils::FormatErrorMessage(kOverQuotaError, name_);
 138 }
 139
 140 QuotaService::SustainedLimit::SustainedLimit(const base::TimeDelta& sustain,
 141                                              const Config& config,
 142                                              BucketMapper* map,
 143                                              const std::string& name)
 144     : QuotaLimitHeuristic(config, map, name),
 145       repeat_exhaustion_allowance_(sustain.InSeconds() /
 146                                    config.refill_interval.InSeconds()),
 147       num_available_repeat_exhaustions_(repeat_exhaustion_allowance_) {}
 148
 149 bool QuotaService::TimedLimit::Apply(Bucket* bucket,
 150                                      const base::TimeTicks& event_time) {
 151   if (event_time > bucket->expiration())
 152     bucket->Reset(config(), event_time);
 153
 154   return bucket->DeductToken();
 155 }
 156
 157 bool QuotaService::SustainedLimit::Apply(Bucket* bucket,
 158                                          const base::TimeTicks& event_time) {
 159   if (event_time > bucket->expiration()) {
 160     // We reset state for this item and start over again if this request breaks
 161     // the bad cycle that was previously being tracked.  This occurs if the
 162     // state in the bucket expired recently (it has been long enough since the
 163     // event that we don't care about the last event), but the bucket still has
 164     // tokens (so pressure was not sustained over that time), OR we are more
 165     // than 1 full refill interval away from the last event (so even if we used
 166     // up all the tokens in the last bucket, nothing happened in the entire
 167     // next refill interval, so it doesn't matter).
 168     if (bucket->has_tokens() ||
 169         event_time > bucket->expiration() + config().refill_interval) {
 170       bucket->Reset(config(), event_time);
 171       num_available_repeat_exhaustions_ = repeat_exhaustion_allowance_;
 172     } else if (--num_available_repeat_exhaustions_ > 0) {
 173       // The last interval was saturated with requests, and this is the first
 174       // event in the next interval. If this happens
 175       // repeat_exhaustion_allowance_ times, it's a violation. Reset the bucket
 176       // state to start timing from the end of the last interval (and we'll
 177       // deduct the token below) so we can detect this each time it happens.
 178       bucket->Reset(config(), bucket->expiration());
 179     } else {
 180       // No allowances left; this request is a violation.
 181       return false;
 182     }
 183   }
 184
 185   // We can go negative since we check has_tokens when we get to *next* bucket,
 186   // and for the small interval all that matters is whether we used up all the
 187   // tokens (which is true if num_tokens_ <= 0).
 188   bucket->DeductToken();
 189   return true;
 190 }
 191
 192 }  // namespace extensions