Quota: Add metrics about the age and amount of data stored in temporary storage, and a metric about…

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 6d7682c46829c760027c59316f3042722fc6447b..daa702fe158a0190da2c1cc929c05ad906d4fba5 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -42900,6 +42900,57 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Quota.AmountDayOldData" units="MB">
+  <owner>micaheln@chromium.org</owner>
+  <summary>
+    Amount of data less than a day old in temporary storage. Logged hourly.
+  </summary>
+</histogram>
+
+<histogram name="Quota.AmountMonthOldData" units="MB">
+  <owner>micaheln@chromium.org</owner>
+  <summary>
+    Amount of one week to one month old data in temporary storage. Logged
+    hourly.
+  </summary>
+</histogram>
+
+<histogram name="Quota.AmountOverYearOldData" units="MB">
+  <owner>micaheln@chromium.org</owner>
+  <summary>
+    Amount of data older than one year in temporary storage. Logged hourly.
+  </summary>
+</histogram>
+
+<histogram name="Quota.AmountSixMonthOldData" units="MB">
+  <owner>micaheln@chromium.org</owner>

[Ilya Sherman, 2016/05/19 04:06:01]

nit: typo in your username ;)

[michaeln, 2016/05/19 19:09:15]

ooops, done, thnx 

+  <summary>
+    Amount of three to six month old data in temporary storage. Logged hourly.
+  </summary>
+</histogram>
+
+<histogram name="Quota.AmountThreeMonthOldData" units="MB">
+  <owner>micaheln@chromium.org</owner>
+  <summary>
+    Amount of one to three month old data in temporary storage. Logged hourly.
+  </summary>
+</histogram>
+
+<histogram name="Quota.AmountWeekOldData" units="MB">
+  <owner>micaheln@chromium.org</owner>
+  <summary>
+    Amount of one day to one week old data in temporary storage. Logged hourly.
+  </summary>
+</histogram>
+
+<histogram name="Quota.AmountYearOldData" units="MB">
+  <owner>micaheln@chromium.org</owner>
+  <summary>
+    Amount of six month to one year old data in temporary storage. Logged
+    hourly.
+  </summary>
+</histogram>
+
 <histogram name="Quota.AvailableDiskSpace" units="MB">
   <owner>micaheln@chromium.org</owner>
   <summary>
@@ -43046,6 +43097,30 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Number of unlimited origins using temporary storage.</summary>
 </histogram>
 
+<histogram name="Quota.OriginAgeInDays" units="days">
+  <owner>michaeln@chromium.org</owner>
+  <summary>
+    How many days it's been since an origin's temporary storage has been
+    accessed. Logged hourly.

[Ilya Sherman, 2016/05/19 04:06:01]

Hmm, this is logged hourly... for which origins?  All known origins?  Open
origins?  Some other set of origins?

[michaeln, 2016/05/19 19:09:15]

For all origins with stored data, updated the commented.

+  </summary>
+</histogram>
+
+<histogram name="Quota.QuotaForOrigin" units="MB">
+  <owner>michaeln@chromium.org</owner>
+  <summary>
+    The quota value computed for an origin using temporary storage. Logged at
+    irregular intervals.

[Ilya Sherman, 2016/05/19 04:06:01]

"Logged at irregular intervals" is pretty mysterious.  Is there some event that
triggers the logging?  Or is there a source of randomness involved somehow?

[michaeln, 2016/05/19 19:09:15]

In the process of writing new data, storage systems consult the quota system for
"usage and quota" to determine if there is sufficient space available for the
new data. This value is logged at the time of that consultation. The frequency
is entirely dependent on how individual websites use the various storage apis.

Translation.... "irregular intervals".

[Ilya Sherman, 2016/05/19 22:31:16]

I think it's worth going into this detail in the histogram description.  Even if
the upshot us nothing more than "irregular intervals", it helps the reader gain
confidence that they understand what's behind those irregular intervals, and
therefore adjust their analysis accordingly.

+  </summary>
+</histogram>
+
+<histogram name="Quota.QuotaForOriginIncognito" units="MB">
+  <owner>michaeln@chromium.org</owner>
+  <summary>
+    The quota value computed for an origin using temporary storage in an
+    incognito profile.  Logged at irregular intervals.
+  </summary>
+</histogram>
+
 <histogram name="Quota.SkippedEvictionRoundsPerHour">
   <owner>tzik@chromium.org</owner>
   <summary>Number of skipped eviction rounds in an hour.</summary>