PBS USGen skiprate (prebid#5887)

* PBS USGen skiprate

* Update pbs-usgen.md

Author: bretg

prebid-server/developers/add-a-privacy-module-java.md

@@ -280,3 +280,42 @@ public class MyPrivacyModule implements PrivacyModule, Loggable {
     }
 }
 ```
+
+## Privacy Trace Log and Analytics
+
+The privacy module interface logs information that analytics adapters may want to consume. For example, if you're an analytics provider
+and want to check whether there was a skipRate config present, you can read the log for `skipped:true` and log however your analytics requires.
+
+For example:
+
+```
+         {
+            "description": "Invocation of Activity Infrastructure.",
+            "activity": "transmitUfpd",
+            "activity_invocation_payload": {
+              "component_type": "BIDDER",
+              "component_name": "bidderA"
+            }
+          },
+          {
+            "description": "Setting the default invocation result.",
+            "allow_by_default": true
+          },
+          {
+            "description": "Processing rule.",
+            "rule_configuration": {
+              "and": [
+                {
+                  "privacy_module": "iab.usgeneral",
+                  "skipped": true,
+                  "result": "ABSTAIN"
+                }
+              ]
+            },
+            "result": "ABSTAIN"
+          },
+```
+
+## Further Reading
+
+- [Building a privacy module](/prebid-server/developers/add-a-privacy-module.html)

prebid-server/features/pbs-usgen.md

@@ -148,6 +148,26 @@ Prebid approach, but they want to process SID 8 with this custom module.
 }
 ```
 
+### Testing
+
+Before turning on the USGen module 100%, some host companies may want to partially enable it in order to gague impact. This can be done using the privacy module `skipRate` parameter. Here's an example account config:
+
+```json5
+{
+    "privacy": {
+        "modules": [{
+                "code": "iab.usgeneral",
+                "skipRate": 95,         // only run on 5% of requests. Default is to run on 100%, i.e. skipRate 0 
+                "config": {
+                    "skipSids": [9]
+                }
+        }]
+    }
+}
+```
+
+In order to utilize this test though, you will need an analytics adapter that can read the Activity Infrastructure log. See [privacy module analytics](/prebid-server/developers/add-a-privacy-module-java.html#privacy-trace-log-and-analytics) for more detail.
+
 ### Troubleshooting
 
 Additional information about the outcoming of privacy module processing can be obtained by setting `ext.prebid.trace: "basic"`.