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content / browser / preloading / preloading_config.cc [blame]
// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "content/browser/preloading/preloading_config.h"
#include <string_view>
#include "base/json/json_reader.h"
#include "base/metrics/field_trial_params.h"
#include "base/values.h"
#include "content/browser/preloading/preloading.h"
#include "content/common/features.h"
#include "content/public/browser/preloading.h"
namespace content {
namespace {
// Allows configuring preloading features via a JSON string. This string should
// contain a JSON array of objects. Each object should specify a preloading_type
// key (a string to specify which preloading type is being configured) and a
// predictor key (a string to specify which predictor is being configured). Then
// each object can specify some parameters to tune. Supported parameters are:
// * holdback: whether this preloading_type, predictor combination should be
// held back for counterfactual evaluation.
// * sampling_likelihood: the fraction of preloading attempts that will be
// logged in UKM. See crbug.com/1411841#c3 to see how the sampling_likelihood
// default values are determined.
constexpr base::FeatureParam<std::string> kPreloadingConfigParam{
&features::kPreloadingConfig, "preloading_config", R"(
[{
"preloading_type": "NoStatePrefetch",
"preloading_predictor": "LinkRel",
"sampling_likelihood": 0.007081
}, {
"preloading_type": "Preconnect",
"preloading_predictor": "PointerDownOnAnchor",
"sampling_likelihood": 0.000127
}, {
"preloading_type": "Prefetch",
"preloading_predictor": "DefaultSearchEngine",
"sampling_likelihood": 0.008527
}, {
"preloading_type": "Prefetch",
"preloading_predictor": "OmniboxTouchDownPredirector",
"sampling_likelihood": 0.154563
}, {
"preloading_type": "Prefetch",
"preloading_predictor": "SpeculationRules",
"sampling_likelihood": 0.001011
}, {
"preloading_type": "Prefetch",
"preloading_predictor": "SpeculationRulesFromIsolatedWorld",
"sampling_likelihood": 1.000000
}, {
"preloading_type": "Prefetch",
"preloading_predictor": "UrlPointerDownOnAnchor",
"sampling_likelihood": 0.002547
}, {
"preloading_type": "Prefetch",
"preloading_predictor": "UrlPointerHoverOnAnchor",
"sampling_likelihood": 1.000000
}, {
"preloading_type": "Prerender",
"preloading_predictor": "BackButtonHover",
"sampling_likelihood": 0.008122
}, {
"preloading_type": "Prerender",
"preloading_predictor": "BackGestureNavigation",
"sampling_likelihood": 0.251189
}, {
"preloading_type": "Prerender",
"preloading_predictor": "DefaultSearchEngine",
"sampling_likelihood": 0.018776
}, {
"preloading_type": "Prerender",
"preloading_predictor": "MouseBackButton",
"sampling_likelihood": 0.086468
}, {
"preloading_type": "Prerender",
"preloading_predictor": "MouseHoverOnNewTabPage",
"sampling_likelihood": 1.000000
}, {
"preloading_type": "Prerender",
"preloading_predictor": "MouseHoverOrMouseDownOnBookmarkBar",
"sampling_likelihood": 0.026712
}, {
"preloading_type": "Prerender",
"preloading_predictor": "OmniboxDirectURLInput",
"sampling_likelihood": 0.006663
}, {
"preloading_type": "Prerender",
"preloading_predictor": "PointerDownOnNewTabPage",
"sampling_likelihood": 0.038652
}, {
"preloading_type": "Prerender",
"preloading_predictor": "SpeculationRules",
"sampling_likelihood": 0.093680
}, {
"preloading_type": "Prerender",
"preloading_predictor": "SpeculationRulesFromIsolatedWorld",
"sampling_likelihood": 1.000000
}, {
"preloading_type": "Prerender",
"preloading_predictor": "TouchOnNewTabPage",
"sampling_likelihood": 1.000000
}, {
"preloading_type": "Prerender",
"preloading_predictor": "UrlPointerDownOnAnchor",
"sampling_likelihood": 0.343166
}, {
"preloading_type": "Prerender",
"preloading_predictor": "UrlPointerHoverOnAnchor",
"sampling_likelihood": 1.000000
}]
)"};
static PreloadingConfig* g_config_override = nullptr;
} // namespace
PreloadingConfig& PreloadingConfig::GetInstance() {
static base::NoDestructor<PreloadingConfig> config;
static bool initialized = false;
if (!initialized) {
config->ParseConfig();
initialized = true;
}
if (g_config_override) {
return *g_config_override;
}
return *config;
}
PreloadingConfig::PreloadingConfig() = default;
PreloadingConfig* PreloadingConfig::OverrideForTesting(
PreloadingConfig* config_override) {
raw_ptr<PreloadingConfig> old_override = g_config_override;
g_config_override = config_override;
return old_override;
}
void PreloadingConfig::ParseConfig() {
entries_.clear();
if (!base::FeatureList::IsEnabled(features::kPreloadingConfig)) {
return;
}
// Throughout parsing the config, if we fail to parse, we silently skip the
// config and use the default values.
std::optional<base::Value> config_value =
base::JSONReader::Read(kPreloadingConfigParam.Get());
if (!config_value) {
return;
}
base::Value::List* entries = config_value->GetIfList();
if (!entries) {
return;
}
for (const base::Value& entry : *entries) {
const base::Value::Dict* config_dict = entry.GetIfDict();
DCHECK(config_dict);
if (!config_dict) {
continue;
}
const std::string* preloading_type =
config_dict->FindString("preloading_type");
DCHECK(preloading_type);
if (!preloading_type) {
continue;
}
const std::string* preloading_predictor =
config_dict->FindString("preloading_predictor");
DCHECK(preloading_predictor);
if (!preloading_predictor) {
continue;
}
entries_.emplace(Key(*preloading_type, *preloading_predictor),
Entry::FromDict(config_dict));
}
}
PreloadingConfig::~PreloadingConfig() = default;
bool PreloadingConfig::ShouldHoldback(PreloadingType preloading_type,
PreloadingPredictor predictor) {
Entry entry = entries_[Key::FromEnums(preloading_type, predictor)];
return entry.holdback_;
}
void PreloadingConfig::SetHoldbackForTesting(PreloadingType preloading_type,
PreloadingPredictor predictor,
bool holdback) {
Entry entry;
entry.holdback_ = holdback;
entries_.emplace(
Key(PreloadingTypeToString(preloading_type), predictor.name()), entry);
}
void PreloadingConfig::SetHoldbackForTesting(std::string_view preloading_type,
std::string_view predictor,
bool holdback) {
Entry entry;
entry.holdback_ = holdback;
entries_.emplace(Key(preloading_type, predictor), entry);
}
double PreloadingConfig::SamplingLikelihood(PreloadingType preloading_type,
PreloadingPredictor predictor) {
Entry entry = entries_[Key::FromEnums(preloading_type, predictor)];
return entry.sampling_likelihood_;
}
PreloadingConfig::Key::Key(std::string_view preloading_type,
std::string_view predictor)
: preloading_type_(preloading_type), predictor_(predictor) {}
PreloadingConfig::Key PreloadingConfig::Key::FromEnums(
PreloadingType preloading_type,
PreloadingPredictor predictor) {
return Key(PreloadingTypeToString(preloading_type), predictor.name());
}
PreloadingConfig::Entry PreloadingConfig::Entry::FromDict(
const base::Value::Dict* dict) {
Entry entry;
std::optional<bool> holdback = dict->FindBool("holdback");
if (holdback) {
entry.holdback_ = *holdback;
}
std::optional<double> sampling_likelihood =
dict->FindDouble("sampling_likelihood");
if (sampling_likelihood) {
entry.sampling_likelihood_ = *sampling_likelihood;
}
return entry;
}
bool PreloadingConfig::KeyCompare::operator()(
const PreloadingConfig::Key& lhs,
const PreloadingConfig::Key& rhs) const {
return std::tie(lhs.preloading_type_, lhs.predictor_) <
std::tie(rhs.preloading_type_, rhs.predictor_);
}
} // namespace content