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// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_METRICS_SINGLE_SAMPLE_METRICS_FACTORY_IMPL_H_
#define COMPONENTS_METRICS_SINGLE_SAMPLE_METRICS_FACTORY_IMPL_H_
#include <string>
#include "base/metrics/single_sample_metrics.h"
#include "components/metrics/public/mojom/single_sample_metrics.mojom.h"
#include "components/metrics/single_sample_metrics.h"
namespace metrics {
// SingleSampleMetricsFactory implementation for creating SingleSampleMetric
// instances that communicate over mojo to instances in another process.
//
// Persistance outside of the current process allows these metrics to record a
// sample even in the event of sudden process termination. As an example, this
// is useful for garbage collected objects which may never get a chance to run
// their destructors in the event of a fast shutdown event (process kill).
class SingleSampleMetricsFactoryImpl : public base::SingleSampleMetricsFactory {
public:
// Constructs a factory capable of vending single sample metrics from any
// thread. |create_provider_cb| will be called from arbitrary threads to
// create providers as necessary; the callback must handle thread safety.
//
// We use a callback here to avoid taking additional DEPS on content and a
// service_manager::Connector() for simplicitly and to avoid the need for
// using the service test harness just for instantiating this class.
explicit SingleSampleMetricsFactoryImpl(CreateProviderCB create_provider_cb);
SingleSampleMetricsFactoryImpl(const SingleSampleMetricsFactoryImpl&) =
delete;
SingleSampleMetricsFactoryImpl& operator=(
const SingleSampleMetricsFactoryImpl&) = delete;
~SingleSampleMetricsFactoryImpl() override;
// base::SingleSampleMetricsFactory:
std::unique_ptr<base::SingleSampleMetric> CreateCustomCountsMetric(
const std::string& histogram_name,
base::HistogramBase::Sample32 min,
base::HistogramBase::Sample32 max,
uint32_t bucket_count) override;
// Providers live forever in production, but tests should be kind and clean up
// after themselves to avoid tests trampling on one another. Destroys the
// provider in the TLS slot for the calling thread.
void DestroyProviderForTesting();
private:
// Creates a single sample metric.
std::unique_ptr<base::SingleSampleMetric> CreateMetric(
const std::string& histogram_name,
base::HistogramBase::Sample32 min,
base::HistogramBase::Sample32 max,
uint32_t bucket_count,
int32_t flags);
// Gets the SingleSampleMetricsProvider for the current thread. If none
// exists, then a new instance is created and set in the TLS slot.
mojom::SingleSampleMetricsProvider* GetProvider();
CreateProviderCB create_provider_cb_;
};
} // namespace metrics
#endif // COMPONENTS_METRICS_SINGLE_SAMPLE_METRICS_FACTORY_IMPL_H_
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