Bug 686948 - Add telemetry for cache hit/miss with/without revalidation. r=mcmanus

netwerk/protocol/http/nsHttpChannel.cpp

@@ -66,6 +66,7 @@
 #include "nsChannelClassifier.h"
 #include "nsIRedirectResultListener.h"
 #include "mozilla/TimeStamp.h"
+#include "mozilla/Telemetry.h"
 
 // True if the local cache should be bypassed when processing a request.
 #define BYPASS_LOCAL_CACHE(loadFlags) \
@@ -128,6 +129,7 @@ nsHttpChannel::nsHttpChannel()
     , mFallingBack(PR_FALSE)
     , mWaitingForRedirectCallback(PR_FALSE)
     , mRequestTimeInitialized(PR_FALSE)
+    , mDidReval(false)
 {
     LOG(("Creating nsHttpChannel [this=%p]\n", this));
     mChannelCreationTime = PR_Now();
@@ -267,6 +269,8 @@ nsHttpChannel::Connect(PRBool firstTime)
             if (NS_FAILED(rv) && event) {
                 event->Revoke();
             }
+            mozilla::Telemetry::Accumulate(
+                    mozilla::Telemetry::HTTP_CACHE_DISPOSITION, kCacheHit);
             return rv;
         }
         else if (mLoadFlags & LOAD_ONLY_FROM_CACHE) {
@@ -974,6 +978,8 @@ nsHttpChannel::ProcessResponse()
         LOG(("  continuation state has been reset"));
     }
 
+    bool successfulReval = false;
+
     // handle different server response categories.  Note that we handle
     // caching or not caching of error pages in
     // nsHttpResponseHead::MustValidate; if you change this switch, update that
@@ -1025,6 +1031,9 @@ nsHttpChannel::ProcessResponse()
             LOG(("ProcessNotModified failed [rv=%x]\n", rv));
             rv = ProcessNormal();
         }
+        else {
+            successfulReval = true;
+        }
         break;
     case 401:
     case 407:
@@ -1060,6 +1069,17 @@ nsHttpChannel::ProcessResponse()
         break;
     }
 
+    if (!mDidReval)
+        mozilla::Telemetry::Accumulate(
+                mozilla::Telemetry::HTTP_CACHE_DISPOSITION, kCacheMissed);
+    else if (successfulReval)
+        mozilla::Telemetry::Accumulate(
+                mozilla::Telemetry::HTTP_CACHE_DISPOSITION, kCacheHitViaReval);
+    else
+        mozilla::Telemetry::Accumulate(
+                mozilla::Telemetry::HTTP_CACHE_DISPOSITION,
+                kCacheMissedViaReval);
+
     return rv;
 }
 
@@ -2666,6 +2686,7 @@ nsHttpChannel::CheckCache()
             if (val)
                 mRequestHead.SetHeader(nsHttp::If_None_Match,
                                        nsDependentCString(val));
+            mDidReval = true;
         }
     }
 

netwerk/protocol/http/nsHttpChannel.h

@@ -366,6 +366,15 @@ private:
 
 protected:
     virtual void DoNotifyListenerCleanup();
+
+private: // cache telemetry
+    enum {
+        kCacheHit = 1,
+        kCacheHitViaReval = 2,
+        kCacheMissedViaReval = 3,
+        kCacheMissed = 4
+    };
+    bool mDidReval;
 };
 
 #endif // nsHttpChannel_h__

toolkit/components/telemetry/TelemetryHistograms.h

@@ -132,6 +132,9 @@ HTTP_HISTOGRAMS(SUB, "subitem: ")
 
 #undef _HTTP_HIST
 #undef HTTP_HISTOGRAMS
+
+HISTOGRAM(HTTP_CACHE_DISPOSITION, 1, 5, 5, LINEAR, "HTTP Cache Hit, Reval, Failed-Reval, Miss")
+
 HISTOGRAM(FIND_PLUGINS, 1, 3000, 10, EXPONENTIAL, "Time spent scanning filesystem for plugins (ms)")
 HISTOGRAM(CHECK_JAVA_ENABLED, 1, 3000, 10, EXPONENTIAL, "Time spent checking if Java is enabled (ms)")