Add ability to configure api_result_limit

In clouds with many containers or objects, listing them via Horizon
can cause a signficant increase of system load.

This patch enables configuration of the API_RESULT_LIMIT setting within
Horizon. This limits the maximum number of objects to display on a
single page before providing a paging element to paginate results.

Change-Id: Ifaf39d6c9bf549428afd7653243c82cd719956f6
Closes-Bug: 1775002

config.yaml

@@ -357,3 +357,10 @@ options:
       twice the number of CPU cores a service unit has. When deployed in
       a LXD container, this default value will be capped to 4 workers
       unless this configuration option is set.
+  api-result-limit:
+    type:  int
+    default:
+    description: |
+      The maximum number of objects (e.g. Swift objects or Glance images) to
+      display on a single page before providing a paging element (a “more” link)
+      to paginate results.

hooks/horizon_contexts.py

@@ -198,6 +198,8 @@ class HorizonContext(OSContextGenerator):
             'multi_domain': False if config('default-domain') else True,
             "default_create_volume": config("default-create-volume"),
             'image_formats': config('image-formats'),
+            'api_result_limit': config('api-result-limit')
+            if config('api-result-limit') > 0 else 1000,
         }
 
         return ctxt

templates/icehouse/local_settings.py

@@ -237,7 +237,7 @@ SECONDARY_ENDPOINT_TYPE = "{{ secondary_endpoint }}"
 # The number of objects (Swift containers/objects or images) to display
 # on a single page before providing a paging element (a "more" link)
 # to paginate results.
-API_RESULT_LIMIT = 1000
+API_RESULT_LIMIT = {{ api_result_limit }}
 API_RESULT_PAGE_SIZE = 20
 
 # The timezone of the server. This should correspond with the timezone

templates/liberty/local_settings.py

@@ -341,7 +341,7 @@ SECONDARY_ENDPOINT_TYPE = "{{ secondary_endpoint }}"
 # The number of objects (Swift containers/objects or images) to display
 # on a single page before providing a paging element (a "more" link)
 # to paginate results.
-API_RESULT_LIMIT = 1000
+API_RESULT_LIMIT = {{ api_result_limit }}
 API_RESULT_PAGE_SIZE = 20
 
 # The size of chunk in bytes for downloading objects from Swift

templates/mitaka/local_settings.py

@@ -421,7 +421,7 @@ SECONDARY_ENDPOINT_TYPE = "{{ secondary_endpoint }}"
 # The number of objects (Swift containers/objects or images) to display
 # on a single page before providing a paging element (a "more" link)
 # to paginate results.
-API_RESULT_LIMIT = 1000
+API_RESULT_LIMIT = {{ api_result_limit }}
 API_RESULT_PAGE_SIZE = 20
 
 # The size of chunk in bytes for downloading objects from Swift

templates/newton/local_settings.py

@@ -456,7 +456,7 @@ SECONDARY_ENDPOINT_TYPE = "{{ secondary_endpoint }}"
 # The number of objects (Swift containers/objects or images) to display
 # on a single page before providing a paging element (a "more" link)
 # to paginate results.
-API_RESULT_LIMIT = 1000
+API_RESULT_LIMIT = {{ api_result_limit }}
 API_RESULT_PAGE_SIZE = 20
 
 # The size of chunk in bytes for downloading objects from Swift

templates/ocata/local_settings.py

@@ -459,7 +459,7 @@ SECONDARY_ENDPOINT_TYPE = "{{ secondary_endpoint }}"
 # The number of objects (Swift containers/objects or images) to display
 # on a single page before providing a paging element (a "more" link)
 # to paginate results.
-API_RESULT_LIMIT = 1000
+API_RESULT_LIMIT = {{ api_result_limit }}
 API_RESULT_PAGE_SIZE = 20
 
 # The size of chunk in bytes for downloading objects from Swift

unit_tests/test_horizon_contexts.py

@@ -139,6 +139,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -164,6 +165,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -189,6 +191,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -214,6 +217,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -240,6 +244,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -269,6 +274,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -294,6 +300,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -319,6 +326,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -349,6 +357,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -374,6 +383,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -399,6 +409,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -425,6 +436,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": True,
                           "default_create_volume": True,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -451,6 +463,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": False,
                           "image_formats": '',
+                          "api_result_limit": 1000,
                           }
                          )
 
@@ -477,6 +490,7 @@ class TestHorizonContexts(CharmTestCase):
                           "allow_password_autocompletion": False,
                           "default_create_volume": True,
                           "image_formats": 'iso qcow2 raw',
+                          "api_result_limit": 1000,
                           }
                          )