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// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/fuchsia_legacymetrics/legacymetrics_histogram_flattener.h"
#include <memory>
#include <utility>
#include <vector>
#include "base/logging.h"
#include "base/metrics/statistics_recorder.h"
namespace fuchsia_legacymetrics {
namespace {
// Serializes changes to histogram metrics as FIDL structs.
// Cannot be used in conjunction with other metrics collection systems (e.g.
// UMA).
class LegacyMetricsHistogramFlattener : public base::HistogramFlattener {
public:
LegacyMetricsHistogramFlattener() : histogram_snapshot_manager_(this) {}
~LegacyMetricsHistogramFlattener() override = default;
LegacyMetricsHistogramFlattener(const LegacyMetricsHistogramFlattener&) =
delete;
LegacyMetricsHistogramFlattener& operator=(
const LegacyMetricsHistogramFlattener&) = delete;
// Returns a vector of changes to histogram data made since the last call to
// this method. Returns all histogram data when invoked for the first time.
std::vector<fuchsia::legacymetrics::Histogram> GetDeltas() {
DCHECK(histogram_deltas_.empty());
// Gather all histogram deltas, which will be sent to RecordDelta() and
// buffered in |histogram_deltas_|.
base::StatisticsRecorder::PrepareDeltas(
// Only return in-memory/non-persisted histograms.
false,
// Do not set flags on histograms.
base::Histogram::kNoFlags,
// Only upload metrics marked for UMA upload.
base::Histogram::kUmaTargetedHistogramFlag,
&histogram_snapshot_manager_);
return std::move(histogram_deltas_);
}
private:
// base::HistogramFlattener implementation.
// Appends the contents of |snapshot| for the specified |histogram| within
// |histogram_deltas_|.
void RecordDelta(const base::HistogramBase& histogram,
const base::HistogramSamples& snapshot) override {
DCHECK_NE(0, snapshot.TotalCount());
DVLOG(3) << "RecordDelta " << histogram.histogram_name();
fuchsia::legacymetrics::Histogram converted;
converted.set_name(std::string(histogram.histogram_name()));
converted.set_sum(snapshot.sum());
for (std::unique_ptr<base::SampleCountIterator> it = snapshot.Iterator();
!it->Done(); it->Next()) {
base::Histogram::Sample32 min;
int64_t max = 0;
base::Histogram::Count32 count;
it->Get(&min, &max, &count);
fuchsia::legacymetrics::HistogramBucket bucket;
bucket.min = min;
bucket.max = max;
bucket.count = count;
DVLOG(4) << " Bucket: [" << min << "," << max << ") = " << count;
converted.mutable_buckets()->emplace_back(std::move(bucket));
}
histogram_deltas_.emplace_back(std::move(converted));
}
base::HistogramSnapshotManager histogram_snapshot_manager_;
std::vector<fuchsia::legacymetrics::Histogram> histogram_deltas_;
};
} // namespace
std::vector<fuchsia::legacymetrics::Histogram> GetLegacyMetricsDeltas() {
return LegacyMetricsHistogramFlattener().GetDeltas();
}
} // namespace fuchsia_legacymetrics
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