Add UMA Precache.Freshness.Prefetch

components/precache/core/precache_database.cc

Index: components/precache/core/precache_database.cc
diff --git a/components/precache/core/precache_database.cc b/components/precache/core/precache_database.cc
index 269eded59dc1da3031a31610d56265cfe8372458..ca5e6421f9a6e3ecf9336834d6df6af3b8b57926 100644
--- a/components/precache/core/precache_database.cc
+++ b/components/precache/core/precache_database.cc
@@ -13,6 +13,7 @@
 #include "base/time/time.h"
 #include "components/history/core/browser/history_constants.h"
 #include "components/precache/core/proto/unfinished_work.pb.h"
+#include "net/http/http_response_headers.h"
 #include "sql/connection.h"
 #include "sql/transaction.h"
 #include "url/gurl.h"
@@ -118,8 +119,8 @@ base::Time PrecacheDatabase::GetLastPrecacheTimestamp() {
 void PrecacheDatabase::RecordURLPrefetch(const GURL& url,
                                          const base::TimeDelta& latency,
                                          const base::Time& fetch_time,
-                                         int64_t size,
-                                         bool was_cached) {
+                                         const net::HttpResponseInfo& info,
+                                         int64_t size) {
   UMA_HISTOGRAM_TIMES("Precache.Latency.Prefetch", latency);
 
   if (!IsDatabaseAccessible()) {
@@ -133,15 +134,27 @@ void PrecacheDatabase::RecordURLPrefetch(const GURL& url,
     Flush();
   }
 
-  if (was_cached && !precache_url_table_.HasURL(url)) {
+  DCHECK(info.headers) << "The headers are required to get the freshness.";
+  if (info.headers) {

[bengr, 2016/07/26 17:29:10]

#include "net/http/http_response_info.h"

[jamartin, 2016/07/26 19:56:22]

Done.

+    UMA_HISTOGRAM_CUSTOM_COUNTS(
+        "Precache.Freshness.Prefetch",
+        info.headers->GetFreshnessLifetimes(info.response_time)
+            .freshness.InSeconds(),
+        base::TimeDelta::FromMinutes(5).InSeconds() /* min */,
+        base::TimeDelta::FromDays(356).InSeconds() /* max */,
+        100 /* bucket_count */);
+  }
+
+  if (info.was_cached && !precache_url_table_.HasURL(url)) {
     // Since the precache came from the cache, and there's no entry in the URL
     // table for the URL, this means that the resource was already in the cache
-    // because of user browsing. Thus, this precache had no effect, so ignore
-    // it.
+    // because of user browsing. Therefore, this precache won't be considered as
+    // precache-motivated since it had no significant effect (besides a possible
+    // revalidation and a change in the cache LRU priority).
     return;
   }
 
-  if (!was_cached) {
+  if (!info.was_cached) {
     // The precache only counts as overhead if it was downloaded over the
     // network.
     UMA_HISTOGRAM_COUNTS("Precache.DownloadedPrecacheMotivated",
@@ -161,8 +174,8 @@ void PrecacheDatabase::RecordURLPrefetch(const GURL& url,
 void PrecacheDatabase::RecordURLNonPrefetch(const GURL& url,
                                             const base::TimeDelta& latency,
                                             const base::Time& fetch_time,
+                                            const net::HttpResponseInfo& info,
                                             int64_t size,
-                                            bool was_cached,
                                             int host_rank,
                                             bool is_connection_cellular) {
   UMA_HISTOGRAM_TIMES("Precache.Latency.NonPrefetch", latency);
@@ -190,14 +203,14 @@ void PrecacheDatabase::RecordURLNonPrefetch(const GURL& url,
     Flush();
   }
 
-  if (was_cached && !precache_url_table_.HasURL(url)) {
+  if (info.was_cached && !precache_url_table_.HasURL(url)) {
     // Ignore cache hits that precache can't take credit for.
     return;
   }
 
   base::HistogramBase::Sample size_sample =
       static_cast<base::HistogramBase::Sample>(size);
-  if (!was_cached) {
+  if (!info.was_cached) {
     // The fetch was served over the network during user browsing, so count it
     // as downloaded non-precache bytes.
     UMA_HISTOGRAM_COUNTS("Precache.DownloadedNonPrecache", size_sample);
@@ -205,7 +218,7 @@ void PrecacheDatabase::RecordURLNonPrefetch(const GURL& url,
       UMA_HISTOGRAM_COUNTS("Precache.DownloadedNonPrecache.Cellular",
                            size_sample);
     }
-  } else {
+  } else {  // info.was_cached.
     // The fetch was served from the cache, and since there's an entry for this
     // URL in the URL table, this means that the resource was served from the
     // cache only because precaching put it there. Thus, precaching was helpful,
@@ -214,6 +227,18 @@ void PrecacheDatabase::RecordURLNonPrefetch(const GURL& url,
     if (is_connection_cellular) {
       UMA_HISTOGRAM_COUNTS("Precache.Saved.Cellular", size_sample);
     }
+
+    DCHECK(info.headers) << "The headers are required to get the freshness.";
+    if (info.headers) {
+      // TODO(jamartin): Maybe report stale_while_validate as well.
+      UMA_HISTOGRAM_CUSTOM_COUNTS(
+          "Precache.Saved.Freshness",
+          info.headers->GetFreshnessLifetimes(info.response_time)
+              .freshness.InSeconds(),
+          base::TimeDelta::FromMinutes(5).InSeconds() /* min */,
+          base::TimeDelta::FromDays(356).InSeconds() /* max */,
+          100 /* bucket_count */);
+    }
   }
 
   // Since the resource has been fetched during user browsing, remove any record