Add a histogram to log the size of an UMA upload.

components/metrics/metrics_service.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 //------------------------------------------------------------------------------
 // Description of the life cycle of a instance of MetricsService.
 //
 //  OVERVIEW
 //
 // A MetricsService instance is typically created at application startup.  It is
@@ skipping 1008 matching lines @@
   // Log a histogram to track response success vs. failure rates.
   UMA_HISTOGRAM_ENUMERATION("UMA.UploadResponseStatus.Protobuf",
                             ResponseCodeToStatus(response_code),
                             NUM_RESPONSE_STATUSES);
 
   bool upload_succeeded = response_code == 200;
 
   // Provide boolean for error recovery (allow us to ignore response_code).
   bool discard_log = false;
   const size_t log_size = log_manager_.staged_log().length();
-  if (!upload_succeeded && log_size > kUploadLogAvoidRetransmitSize) {
+  if (upload_succeeded) {
+    UMA_HISTOGRAM_COUNTS_10000("UMA.LogSize", log_size / 1024);

[Ilya Sherman, 2014/08/30 01:23:23]

Hmm, why not record this for all logs when sending the upload, rather than only
for successful logs after the upload response is received?  I guess it's not
obvious to me which is more useful; but the filtering by success does seem like
it could limit visibility into any potential problems with discarding large
logs.

[Alexei Svitkine (slow), 2014/09/02 14:50:37]

I want to use this histogram to capture how much data is sent up to Google
servers (and do so client-side so that e.g. I can see the effect of experiments
on this - e.g. playing with upload frequency), so I'm only interested in
successes (to avoid e.g. double counting on re-transmissions).

+  } else if (log_size > kUploadLogAvoidRetransmitSize) {
     UMA_HISTOGRAM_COUNTS("UMA.Large Rejected Log was Discarded",
                          static_cast<int>(log_size));
     discard_log = true;
   } else if (response_code == 400) {
     // Bad syntax.  Retransmission won't work.
     discard_log = true;
   }
 
   if (upload_succeeded || discard_log) {
     log_manager_.DiscardStagedLog();
@@ skipping 146 matching lines @@
   local_state_->SetBoolean(path, value);
   RecordCurrentState(local_state_);
 }
 
 void MetricsService::RecordCurrentState(PrefService* pref) {
   pref->SetInt64(metrics::prefs::kStabilityLastTimestampSec,
                  base::Time::Now().ToTimeT());
 }
 
 }  // namespace metrics