1 // Copyright (c) 2012 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 #ifndef BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_ 6 #define BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_ 7 8 #include <stdint.h> 9 10 #include <map> 11 #include <string> 12 #include <vector> 13 14 #include "base/gtest_prod_util.h" 15 #include "base/macros.h" 16 #include "base/metrics/histogram_base.h" 17 18 namespace base { 19 20 class HistogramSamples; 21 class HistogramFlattener; 22 23 // HistogramSnapshotManager handles the logistics of gathering up available 24 // histograms for recording either to disk or for transmission (such as from 25 // renderer to browser, or from browser to UMA upload). Since histograms can sit 26 // in memory for an extended period of time, and are vulnerable to memory 27 // corruption, this class also validates as much rendundancy as it can before 28 // calling for the marginal change (a.k.a., delta) in a histogram to be 29 // recorded. 30 class BASE_EXPORT HistogramSnapshotManager { 31 public: 32 explicit HistogramSnapshotManager(HistogramFlattener* histogram_flattener); 33 virtual ~HistogramSnapshotManager(); 34 35 // Snapshot all histograms, and ask |histogram_flattener_| to record the 36 // delta. |flags_to_set| is used to set flags for each histogram. 37 // |required_flags| is used to select histograms to be recorded. 38 // Only histograms that have all the flags specified by the argument will be 39 // chosen. If all histograms should be recorded, set it to 40 // |Histogram::kNoFlags|. 41 template <class ForwardHistogramIterator> PrepareDeltas(ForwardHistogramIterator begin,ForwardHistogramIterator end,HistogramBase::Flags flags_to_set,HistogramBase::Flags required_flags)42 void PrepareDeltas(ForwardHistogramIterator begin, 43 ForwardHistogramIterator end, 44 HistogramBase::Flags flags_to_set, 45 HistogramBase::Flags required_flags) { 46 for (ForwardHistogramIterator it = begin; it != end; ++it) { 47 (*it)->SetFlags(flags_to_set); 48 if (((*it)->flags() & required_flags) == required_flags) 49 PrepareDelta(*it); 50 } 51 } 52 53 // When the collection is not so simple as can be done using a single 54 // iterator, the steps can be performed separately. Call PerpareDelta() 55 // as many times as necessary. PrepareFinalDelta() works like PrepareDelta() 56 // except that it does not update the previous logged values and can thus 57 // be used with read-only files. 58 void PrepareDelta(HistogramBase* histogram); 59 void PrepareFinalDelta(const HistogramBase* histogram); 60 61 private: 62 FRIEND_TEST_ALL_PREFIXES(HistogramSnapshotManagerTest, CheckMerge); 63 64 // During a snapshot, samples are acquired and aggregated. This structure 65 // contains all the information for a given histogram that persists between 66 // collections. 67 struct SampleInfo { 68 // The set of inconsistencies (flags) already seen for the histogram. 69 // See HistogramBase::Inconsistency for values. 70 uint32_t inconsistencies = 0; 71 }; 72 73 // Capture and hold samples from a histogram. This does all the heavy 74 // lifting for PrepareDelta() and PrepareAbsolute(). 75 void PrepareSamples(const HistogramBase* histogram, 76 std::unique_ptr<HistogramSamples> samples); 77 78 // Try to detect and fix count inconsistency of logged samples. 79 void InspectLoggedSamplesInconsistency( 80 const HistogramSamples& new_snapshot, 81 HistogramSamples* logged_samples); 82 83 // For histograms, track what has been previously seen, indexed 84 // by the hash of the histogram name. 85 std::map<uint64_t, SampleInfo> known_histograms_; 86 87 // |histogram_flattener_| handles the logistics of recording the histogram 88 // deltas. 89 HistogramFlattener* histogram_flattener_; // Weak. 90 91 DISALLOW_COPY_AND_ASSIGN(HistogramSnapshotManager); 92 }; 93 94 } // namespace base 95 96 #endif // BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_ 97