doc/ap: document default archive policies and tweak them

Medium default archive policy go for one minute resolution over a day.
High was way too big, reduce it a bit.

Change-Id: I4ac19fdb9c85a3a14232353b4f2535153a6ded74

doc/source/architecture.rst

@@ -54,7 +54,7 @@ largely more scalable. Ceph also offers better consistency, and hence is the
 recommended driver.
 
 How to plan for Gnocchi’s storage
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+---------------------------------
 
 Gnocchi uses a custom file format based on its library *Carbonara*. In Gnocchi,
 a time series is a collection of points, where a point is a given measure, or
@@ -84,7 +84,7 @@ the 8 default aggregation methods (mean, min, max, sum, std, median, count,
 used will go up to a maximum of 8 × 4.5 MiB = 36 MiB.
 
 How to set the archive policy and granularity
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+---------------------------------------------
 
 In Gnocchi, the archive policy is expressed in number of points. If your
 archive policy defines a policy of 10 points with a granularity of 1 second,
@@ -109,3 +109,28 @@ policies. A typical low grained use case could be::
 This would represent 7205 points × 17.92 = 126 KiB per aggregation method. If
 you use the 8 standard aggregation method, your metric will take up to 8 × 126
 KiB = 0.98 MiB of disk space.
+
+Default archive policies
+------------------------
+
+By default, 3 archive policies are created using the default archive policy
+list (listed in `default_aggregation_methods`, i.e. mean, min, max, sum, std,
+median, count, 95pct):
+
+- low (maximum estimated size per metric: 5 KiB)
+
+  * 5 minutes granularity over 1 hour
+  * 1 hour granularity over 1 day
+  * 1 day granularity over 1 month
+
+- medium (maximum estimated size per metric: 139 KiB)
+
+  * 1 minute granularity over 1 day
+  * 1 hour granularity over 1 week
+  * 1 day granularity over 1 year
+
+- high (maximum estimated size per metric: 1 578 KiB)
+
+  * 1 second granularity over 1 hour
+  * 1 minute granularity over 1 week
+  * 1 hour granularity over 1 year

gnocchi/archive_policy.py

@@ -222,8 +222,8 @@ DEFAULT_ARCHIVE_POLICIES = {
     ),
     'medium': ArchivePolicy(
         "medium", 0, [
-            # 1 minute resolution for an hour
-            ArchivePolicyItem(granularity=60, points=60),
+            # 1 minute resolution for an day
+            ArchivePolicyItem(granularity=60, points=60 * 24),
             # 1 hour resolution for a week
             ArchivePolicyItem(granularity=3600, points=7 * 24),
             # 1 day resolution for a year
@@ -232,10 +232,10 @@ DEFAULT_ARCHIVE_POLICIES = {
     ),
     'high': ArchivePolicy(
         "high", 0, [
-            # 1 second resolution for a day
-            ArchivePolicyItem(granularity=1, points=3600 * 24),
-            # 1 minute resolution for a month
-            ArchivePolicyItem(granularity=60, points=60 * 24 * 30),
+            # 1 second resolution for an hour
+            ArchivePolicyItem(granularity=1, points=3600),
+            # 1 minute resolution for a week
+            ArchivePolicyItem(granularity=60, points=60 * 24 * 7),
             # 1 hour resolution for a year
             ArchivePolicyItem(granularity=3600, points=365 * 24),
         ],

gnocchi/tests/gabbi/gabbits-live/live.yaml

@@ -17,9 +17,9 @@ tests:
       response_headers:
           content-type: /application/json/
       response_strings:
-          - '{"definition": [{"points": 86400, "timespan": "1 day, 0:00:00", "granularity": "0:00:01"}, {"points": 43200, "timespan": "30 days, 0:00:00", "granularity": "0:01:00"}, {"points": 8760, "timespan": "365 days, 0:00:00", "granularity": "1:00:00"}], "back_window": 0, "name": "high", "aggregation_methods": ["std", "count", "95pct", "min", "max", "sum", "median", "mean"]}'
+          - '{"definition": [{"points": 3600, "timespan": "1:00:00", "granularity": "0:00:01"}, {"points": 10080, "timespan": "7 days, 0:00:00", "granularity": "0:01:00"}, {"points": 8760, "timespan": "365 days, 0:00:00", "granularity": "1:00:00"}], "back_window": 0, "name": "high", "aggregation_methods": ["std", "count", "95pct", "min", "max", "sum", "median", "mean"]}'
           - '{"definition": [{"points": 12, "timespan": "1:00:00", "granularity": "0:05:00"}, {"points": 24, "timespan": "1 day, 0:00:00", "granularity": "1:00:00"}, {"points": 30, "timespan": "30 days, 0:00:00", "granularity": "1 day, 0:00:00"}], "back_window": 0, "name": "low", "aggregation_methods": ["std", "count", "95pct", "min", "max", "sum", "median", "mean"]}'
-          - '{"definition": [{"points": 60, "timespan": "1:00:00", "granularity": "0:01:00"}, {"points": 168, "timespan": "7 days, 0:00:00", "granularity": "1:00:00"}, {"points": 365, "timespan": "365 days, 0:00:00", "granularity": "1 day, 0:00:00"}], "back_window": 0, "name": "medium", "aggregation_methods": ["std", "count", "95pct", "min", "max", "sum", "median", "mean"]}'
+          - '{"definition": [{"points": 1440, "timespan": "1 day, 0:00:00", "granularity": "0:01:00"}, {"points": 168, "timespan": "7 days, 0:00:00", "granularity": "1:00:00"}, {"points": 365, "timespan": "365 days, 0:00:00", "granularity": "1 day, 0:00:00"}], "back_window": 0, "name": "medium", "aggregation_methods": ["std", "count", "95pct", "min", "max", "sum", "median", "mean"]}'
 
     - name: check generic resources with the default one for statsd
       url: /v1/resource/generic