Merge pull request #37 from edx/dkaplan1/document-stricter-masking

feat: documenting the new privacy flag

README.md

@@ -9,6 +9,12 @@ Status](https://api.travis-ci.com/edx/frontend-logging.svg?branch=master)](https
 
 frontend-logging contains a shared interface for logging errors and events to Datadog.
 
+When you use ``logError``, your errors will appear under browser logs for your Browser application.
+
+You can also add your own custom metrics as an additional argument, or see the code to find other standard custom attributes.
+
+General Logging service interface is defined in [frontend-platform](https://openedx.github.io/frontend-platform/module-Logging.LoggingService.html).
+
 ## Usage
 
 To install frontend-logging into your project::
@@ -31,8 +37,14 @@ In the `env.config.js` file, add the following
 
 The DatadogLoggingService is a concrete implementation of the logging service interface that sends messages to Datadog that can be seen in Datadog RUM and Datadog browser logs. When in development mode, all messages will instead be sent to the console.
 
-When you use ``logError``, your errors will appear under broswer logs for your Browser application.
-
-You can also add your own custom metrics as an additional argument, or see the code to find other standard custom attributes.
-
-General Logging service interface is defined in [frontend-platform](https://openedx.github.io/frontend-platform/module-Logging.LoggingService.html).
+There are a number of variables you can set to configure RUM logging in Datadog. In our environment, these are probably set in `edx-internal`, in `frontends/[name of your frontend app]/[env]_config.yml`:
+
+- `DATADOG_APPLICATION_ID`: Provided by Datadog during RUM configuration.
+- `DATADOG_CLIENT_TOKEN`: Provided by Datadog during RUM configuration.
+- `DATADOG_SITE`: Provided by Datadog during RUM configuration. Probably `datadoghq.com`.
+- `DATADOG_SERVICE`: Provided by Datadog during RUM configuration. This will be the name of your frontend.
+- `DATADOG_ENV`: Environment for the config. (ie. `stg`, `prod`, `edge`)
+- `DATADOG_SESSION_SAMPLE_RATE`: How many sessions should we capture RUM data from. This has cost implictions, so if you don't have unique needs, copy the most common setting you see in prior art.
+- `DATADOG_SESSION_REPLAY_SAMPLE_RATE`: How many sessions should we capture for replay. This has cost implictions, so if you don't have unique needs, copy the most common setting you see in prior art.
+- `DATADOG_LOGS_SESSION_SAMPLE_RATE`: How many sessions should we capture logs from. This has cost implictions, so if you don't have unique needs, copy the most common setting you see in prior art.
+- `DATADOG_PRIVACY_LEVEL`: (**Optional**) The privacy masking setting used for saved sessions. Defaults to masking only user input. [For legal values, see Datadog's session privacy docs](https://docs.datadoghq.com/real_user_monitoring/session_replay/privacy_options).