Measuring data use of different ModelTypes in Sync Service.

sync/engine/commit.cc

Index: sync/engine/commit.cc
diff --git a/sync/engine/commit.cc b/sync/engine/commit.cc
index f607be4c8b4e91499e2d1184c9c8d491d6b0d7ba..ae9128ef758f3620def77fa5a9dea51b39bced43 100644
--- a/sync/engine/commit.cc
+++ b/sync/engine/commit.cc
@@ -4,6 +4,7 @@
 
 #include "sync/engine/commit.h"
 
+#include "base/metrics/sparse_histogram.h"
 #include "base/trace_event/trace_event.h"
 #include "sync/engine/commit_contribution.h"
 #include "sync/engine/commit_processor.h"
@@ -14,6 +15,13 @@
 #include "sync/internal_api/public/events/commit_response_event.h"
 #include "sync/sessions/sync_session.h"
 
+#define UMA_HISTOGRAM_SPARSE_SLOWLY_WITH_VALUE(name, sample, value)     \
+  do {                                                                  \
+    base::HistogramBase* histogram = base::SparseHistogram::FactoryGet( \
+        name, base::HistogramBase::kUmaTargetedHistogramFlag);          \
+    histogram->AddCount(sample, value);                                 \
+  } while (0)
+
 namespace syncer {
 
 Commit::Commit(ContributionMap contributions,
@@ -70,11 +78,22 @@ Commit* Commit::Init(
       enabled_types,
       commit_message);
 
+  int previous_message_size = message.ByteSize();
   // Finally, serialize all our contributions.
   for (std::map<ModelType, CommitContribution*>::const_iterator it =
            contributions.begin();
        it != contributions.end(); ++it) {
     it->second->AddToCommitMessage(&message);
+    int current_entry_size = message.ByteSize() - previous_message_size;
+    previous_message_size = message.ByteSize();
+    if (current_entry_size > 0) {
+      UMA_HISTOGRAM_SPARSE_SLOWLY_WITH_VALUE("DataUse.Sync.Upload.Bytes",

[sclittle, 2015/08/10 23:39:39]

Could you test somewhere that these histograms are recorded properly in
unittests? Maybe in sync/engine/syncer_unittest.cc.

HistogramTester might be useful:
https://code.google.com/p/chromium/codesearch#chromium/src/base/test/histogra...

[amohammadkhan, 2015/08/11 21:04:44]

Thank you for your helpful suggestions. Done.

+                                             ModelTypeToHistogramInt(it->first),
+                                             current_entry_size);
+    }
+    UMA_HISTOGRAM_SPARSE_SLOWLY_WITH_VALUE("DataUse.Sync.Upload.Count",

[sclittle, 2015/08/10 23:39:39]

If you're just incrementing by one, could you just use the normal
UMA_HISTOGRAM_SPARSE_SLOWLY?

[amohammadkhan, 2015/08/11 21:04:44]

Done.

+                                           ModelTypeToHistogramInt(it->first),
+                                           1);
   }
 
   // If we made it this far, then we've successfully prepared a commit message.