base/metrics/histogram_snapshot_manager.h

   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 <map>
   9 #include <string>
  10
  11 #include "base/basictypes.h"
  12 #include "base/metrics/histogram_base.h"
  13
  14 namespace base {
  15
  16 class HistogramSamples;
  17 class HistogramFlattener;
  18
  19 // HistogramSnapshotManager handles the logistics of gathering up available
  20 // histograms for recording either to disk or for transmission (such as from
  21 // renderer to browser, or from browser to UMA upload). Since histograms can sit
  22 // in memory for an extended period of time, and are vulnerable to memory
  23 // corruption, this class also validates as much rendundancy as it can before
  24 // calling for the marginal change (a.k.a., delta) in a histogram to be
  25 // recorded.
  26 class BASE_EXPORT HistogramSnapshotManager {
  27  public:
  28   explicit HistogramSnapshotManager(HistogramFlattener* histogram_flattener);
  29   virtual ~HistogramSnapshotManager();
  30
  31   // Snapshot all histograms, and ask |histogram_flattener_| to record the
  32   // delta. |flags_to_set| is used to set flags for each histogram.
  33   // |required_flags| is used to select histograms to be recorded.
  34   // Only histograms that have all the flags specified by the argument will be
  35   // chosen. If all histograms should be recorded, set it to
  36   // |Histogram::kNoFlags|.
  37   void PrepareDeltas(HistogramBase::Flags flags_to_set,
  38                      HistogramBase::Flags required_flags);
  39
  40  private:
  41   // Snapshot this histogram, and record the delta.
  42   void PrepareDelta(const HistogramBase& histogram);
  43
  44   // Try to detect and fix count inconsistency of logged samples.
  45   void InspectLoggedSamplesInconsistency(
  46       const HistogramSamples& new_snapshot,
  47       HistogramSamples* logged_samples);
  48
  49   // For histograms, track what we've already recorded (as a sample for
  50   // each histogram) so that we can record only the delta with the next log.
  51   std::map<std::string, HistogramSamples*> logged_samples_;
  52
  53   // List of histograms found to be corrupt, and their problems.
  54   std::map<std::string, int> inconsistencies_;
  55
  56   // |histogram_flattener_| handles the logistics of recording the histogram
  57   // deltas.
  58   HistogramFlattener* histogram_flattener_;  // Weak.
  59
  60   DISALLOW_COPY_AND_ASSIGN(HistogramSnapshotManager);
  61 };
  62
  63 }  // namespace base
  64
  65 #endif  // BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_