UMA for data reduction proxy probe net errors

components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc

Index: components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc
diff --git a/components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc b/components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc
index 7fc8138de326a4baa481d2642762af870fa2470a..70d182177fe6ad9e68980716e0547b161cb0fa74 100644
--- a/components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc
+++ b/components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc
@@ -8,6 +8,7 @@
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
+#include "base/metrics/sparse_histogram.h"
 #include "base/prefs/pref_member.h"
 #include "base/prefs/pref_service.h"
 #include "base/prefs/scoped_user_pref_update.h"
@@ -53,6 +54,9 @@ const char kUMAProxyStartupStateHistogram[] =
 // Key of the UMA DataReductionProxy.ProbeURL histogram.
 const char kUMAProxyProbeURL[] = "DataReductionProxy.ProbeURL";
 
+// Key of the UMA DataReductionProxy.ProbeURLNetError histogram.
+const char kUMAProxyProbeURLNetError[] = "DataReductionProxy.ProbeURLNetError";
+
 // Record a network change event.
 void RecordNetworkChangeEvent(DataReductionProxyNetworkChangeEvent event) {
   UMA_HISTOGRAM_ENUMERATION("DataReductionProxy.NetworkChangeEvents",
@@ -234,10 +238,16 @@ void DataReductionProxySettings::OnURLFetchComplete(
 
   DCHECK(source == fetcher_.get());
   net::URLRequestStatus status = source->GetStatus();
-  if (status.status() == net::URLRequestStatus::FAILED &&
-      status.error() == net::ERR_INTERNET_DISCONNECTED) {
-    RecordProbeURLFetchResult(INTERNET_DISCONNECTED);
-    return;
+  if (status.status() == net::URLRequestStatus::FAILED) {
+    if (status.error() == net::ERR_INTERNET_DISCONNECTED) {
+      RecordProbeURLFetchResult(INTERNET_DISCONNECTED);
+      return;
+    }
+    // TODO(bengr): Remove once we understand the reasons probes are failing.
+    // Probe errors are either due to fetcher-level errors or modified
+    // responses. This only tracks the former.
+    UMA_HISTOGRAM_SPARSE_SLOWLY(
+        kUMAProxyProbeURLNetError, std::abs(status.error()));

[mmenke, 2014/07/25 18:27:00]

    UMA_HISTOGRAM_CUSTOM_ENUMERATION(kUMAProxyProbeURLNetError,
                                     std::abs(status.error()),
                                     net::GetAllErrorCodesForUma());

[Alexei Svitkine (slow), 2014/07/25 18:28:21]

No, sparse histogram is better in this case, as it avoids allocating a giant
array for all the possible net buckets.

   }
 
   std::string response;