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// 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 "chrome/browser/extensions/extensions_quota_service.h"
#include "base/message_loop.h"
#include "base/stl_util.h"
#include "chrome/browser/extensions/extension_function.h"
#include "extensions/common/error_utils.h"
namespace {
// If the browser stays open long enough, we reset state once a day.
// Whatever this value is, it should be an order of magnitude longer than
// the longest interval in any of the QuotaLimitHeuristics in use.
const int kPurgeIntervalInDays = 1;
const char kOverQuotaError[] = "This request exceeds the * quota.";
} // namespace
ExtensionsQuotaService::ExtensionsQuotaService() {
if (MessageLoop::current() != NULL) { // Null in unit tests.
purge_timer_.Start(FROM_HERE,
base::TimeDelta::FromDays(kPurgeIntervalInDays),
this, &ExtensionsQuotaService::Purge);
}
}
ExtensionsQuotaService::~ExtensionsQuotaService() {
DCHECK(CalledOnValidThread());
purge_timer_.Stop();
Purge();
}
std::string ExtensionsQuotaService::Assess(
const std::string& extension_id,
ExtensionFunction* function,
const ListValue* args,
const base::TimeTicks& event_time) {
DCHECK(CalledOnValidThread());
if (function->ShouldSkipQuotaLimiting())
return "";
// Lookup function list for extension.
FunctionHeuristicsMap& functions = function_heuristics_[extension_id];
// Lookup heuristics for function, create if necessary.
QuotaLimitHeuristics& heuristics = functions[function->name()];
if (heuristics.empty())
function->GetQuotaLimitHeuristics(&heuristics);
if (heuristics.empty())
return ""; // No heuristic implies no limit.
ViolationErrorMap::iterator violation_error =
violation_errors_.find(extension_id);
if (violation_error != violation_errors_.end())
return violation_error->second; // Repeat offender.
QuotaLimitHeuristic* failed_heuristic = NULL;
for (QuotaLimitHeuristics::iterator heuristic = heuristics.begin();
heuristic != heuristics.end(); ++heuristic) {
// Apply heuristic to each item (bucket).
if (!(*heuristic)->ApplyToArgs(args, event_time)) {
failed_heuristic = *heuristic;
break;
}
}
if (!failed_heuristic)
return "";
std::string error = failed_heuristic->GetError();
DCHECK_GT(error.length(), 0u);
PurgeFunctionHeuristicsMap(&functions);
function_heuristics_.erase(extension_id);
violation_errors_[extension_id] = error;
return error;
}
void ExtensionsQuotaService::PurgeFunctionHeuristicsMap(
FunctionHeuristicsMap* map) {
FunctionHeuristicsMap::iterator heuristics = map->begin();
while (heuristics != map->end()) {
STLDeleteElements(&heuristics->second);
map->erase(heuristics++);
}
}
void ExtensionsQuotaService::Purge() {
DCHECK(CalledOnValidThread());
std::map<std::string, FunctionHeuristicsMap>::iterator it =
function_heuristics_.begin();
for (; it != function_heuristics_.end(); function_heuristics_.erase(it++))
PurgeFunctionHeuristicsMap(&it->second);
}
void QuotaLimitHeuristic::Bucket::Reset(const Config& config,
const base::TimeTicks& start) {
num_tokens_ = config.refill_token_count;
expiration_ = start + config.refill_interval;
}
void QuotaLimitHeuristic::SingletonBucketMapper::GetBucketsForArgs(
const ListValue* args,
BucketList* buckets) {
buckets->push_back(&bucket_);
}
QuotaLimitHeuristic::QuotaLimitHeuristic(const Config& config,
BucketMapper* map,
const std::string& name)
: config_(config), bucket_mapper_(map), name_(name) {
}
QuotaLimitHeuristic::~QuotaLimitHeuristic() {}
bool QuotaLimitHeuristic::ApplyToArgs(const ListValue* args,
const base::TimeTicks& event_time) {
BucketList buckets;
bucket_mapper_->GetBucketsForArgs(args, &buckets);
for (BucketList::iterator i = buckets.begin(); i != buckets.end(); ++i) {
if ((*i)->expiration().is_null()) // A brand new bucket.
(*i)->Reset(config_, event_time);
if (!Apply(*i, event_time))
return false; // It only takes one to spoil it for everyone.
}
return true;
}
std::string QuotaLimitHeuristic::GetError() const {
return extensions::ErrorUtils::FormatErrorMessage(kOverQuotaError, name_);
}
ExtensionsQuotaService::SustainedLimit::SustainedLimit(
const base::TimeDelta& sustain,
const Config& config,
BucketMapper* map,
const std::string& name)
: QuotaLimitHeuristic(config, map, name),
repeat_exhaustion_allowance_(sustain.InSeconds() /
config.refill_interval.InSeconds()),
num_available_repeat_exhaustions_(repeat_exhaustion_allowance_) {
}
bool ExtensionsQuotaService::TimedLimit::Apply(Bucket* bucket,
const base::TimeTicks& event_time) {
if (event_time > bucket->expiration())
bucket->Reset(config(), event_time);
return bucket->DeductToken();
}
bool ExtensionsQuotaService::SustainedLimit::Apply(Bucket* bucket,
const base::TimeTicks& event_time) {
if (event_time > bucket->expiration()) {
// We reset state for this item and start over again if this request breaks
// the bad cycle that was previously being tracked. This occurs if the
// state in the bucket expired recently (it has been long enough since the
// event that we don't care about the last event), but the bucket still has
// tokens (so pressure was not sustained over that time), OR we are more
// than 1 full refill interval away from the last event (so even if we used
// up all the tokens in the last bucket, nothing happened in the entire
// next refill interval, so it doesn't matter).
if (bucket->has_tokens() || event_time > bucket->expiration() +
config().refill_interval) {
bucket->Reset(config(), event_time);
num_available_repeat_exhaustions_ = repeat_exhaustion_allowance_;
} else if (--num_available_repeat_exhaustions_ > 0) {
// The last interval was saturated with requests, and this is the first
// event in the next interval. If this happens
// repeat_exhaustion_allowance_ times, it's a violation. Reset the bucket
// state to start timing from the end of the last interval (and we'll
// deduct the token below) so we can detect this each time it happens.
bucket->Reset(config(), bucket->expiration());
} else {
// No allowances left; this request is a violation.
return false;
}
}
// We can go negative since we check has_tokens when we get to *next* bucket,
// and for the small interval all that matters is whether we used up all the
// tokens (which is true if num_tokens_ <= 0).
bucket->DeductToken();
return true;
}
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