Fixes #2944, #2947 - Read experiment variation values from envvars

config/__init__.py

@@ -119,6 +119,29 @@ def update_status_config(milestones_content):
     return STATUSES
 
 
+def get_variation(variation_key, variations_dict, defaults_dict):
+    """Convert a string to a tuple of integers.
+
+    If the passed variation_key doesn't follow this pattern '0 100', it will
+    return default values defined in defaults_dict.
+
+    This is currently used for defining the variation data of the A/B
+    experiment regarding the multi-steps form.
+    """
+    try:
+        # We want to create a tuple of integers from a string containing
+        # integers. Anything else should throw.
+        rv = tuple(int(x) for x in variations_dict.get(variation_key)
+                                                  .strip().split())
+        if (len(rv) != 2):
+            raise ValueError('The format is incorrect. Expected "{int} {int}"')
+    except Exception as e:
+        print('Something went wrong with AB test configuration: {0}'.format(e))
+        print('Falling back to default values.')
+        rv = defaults_dict.get(variation_key)
+    return rv
+
+
 THREADS_PER_PAGE = 8
 
 # ~3 months-ish expires for static junk
@@ -200,14 +223,29 @@ def update_status_config(milestones_content):
     'type-webvr',
 ]
 
+# Get AB experiment variation values from the environement.
+AB_VARIATIONS = {
+    'FORM_V1_VARIATION': os.environ.get('FORM_V1_VARIATION'),
+    'FORM_V2_VARIATION': os.environ.get('FORM_V2_VARIATION'),
+}
+# We define default values here, as a fallback.
+# By default, v1 will be served 100% of the time.
+AB_DEFAULTS = {
+    'FORM_V1_VARIATION': (0, 100),
+    'FORM_V2_VARIATION': (100, 100),
+}
+EXP_MAX_AGE = int(os.environ.get('EXP_MAX_AGE', 0))
+
 # AB testing config
 AB_EXPERIMENTS = {
     'exp': {
         'variations': {
-            'form-v1': (0, 100),
-            'form-v2': (100, 100)
+            'form-v1': get_variation('FORM_V1_VARIATION', AB_VARIATIONS,
+                                     AB_DEFAULTS),
+            'form-v2': get_variation('FORM_V2_VARIATION', AB_VARIATIONS,
+                                     AB_DEFAULTS),
         },
-        'max-age': None
+        'max-age': EXP_MAX_AGE
     }
 }
 

docs/ab-testing.md

@@ -1,10 +1,23 @@
 # AB testing
 ## Configuration
-You can enable/disable AB testing support by configuring the `config.AB_EXPERIMENT` dictionary.
-This will configure flask to set cookies to responses. For example:
+You can enable/disable AB testing support by configuring the following environment variables:
 
+`FORM_V1_VARIATION`: expects a string of the format '{int} {int}'
+`FORM_V2_VARIATION`: expects a string of the format '{int} {int}'
+`EXP_MAX_AGE`: expects a number which defines when the experiment cookie expires
+
+These are read by the `config.AB_EXPERIMENT` dictionary in `./config/__init__.py` and converted to a tuple.
+This will configure flask to set cookies to responses. For example, setting the variables to the following:
+
+```
+export FORM_V1_VARIATION = "0 20"
+export FORM_V2_VARIATION = "20 100"
+export EXP_MAX_AGE = 604800
 ```
 
+This will result in the `AB_EXPERIMENTS` dictionary with the following values:
+
+```
 AB_EXPERIMENTS = {
     'exp-1': {
         'variations': {

tests/unit/test_config.py

@@ -11,6 +11,7 @@
 import unittest
 
 from config import update_status_config
+from config import get_variation
 from webcompat import webcompat
 
 
@@ -53,6 +54,20 @@ def test_update_status_config(self):
         actual = update_status_config(milestones_json)
         self.assertEqual(actual, expected)
 
+    def test_get_variation(self):
+        """
+        Check the conversion from string to tuples of two int.
+        """
+        defs = {'a': (1, 2)}
+        self.assertTupleEqual((1, 2), get_variation('a', {'a': '1 2'}, defs))
+        self.assertTupleEqual((1, 2), get_variation('a', {'a': None}, defs))
+        self.assertTupleEqual((1, 2), get_variation('a', {'a': ''}, defs))
+        self.assertTupleEqual((1, 2), get_variation('a', {'a': 2}, defs))
+        self.assertTupleEqual((1, 2), get_variation('a', {'a': '1 2 3'}, defs))
+        self.assertTupleEqual((1, 2), get_variation('a', {'a': '1 '}, defs))
+        self.assertTupleEqual((1, 2),
+                              get_variation('a', {'a': '  1 2 '}, defs))
+
 
 if __name__ == '__main__':
     unittest.main()