Add details regarding pseudonymization on the GSC

- Implementation details
- Notes about user_id being pseudonymized
- SQL examples

doc/development/snowplow/implementation.md

@@ -21,8 +21,25 @@ For the recommended frontend tracking implementation, see [Usage recommendations
 Structured events and page views include the [`gitlab_standard`](schemas.md#gitlab_standard)
 context, using the `window.gl.snowplowStandardContext` object which includes
 [default data](https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/views/layouts/_snowplow.html.haml)
-as base. This object can be modified for any subsequent structured event fired,
-although it's not recommended.
+as base:
+
+| Property | Example |
+| -------- | ------- |
+| `context_generated_at` | `"2022-01-01T01:00:00.000Z"` |
+| `environment` | `"production"` |
+| `extra` | `{}` |
+| `namespace_id` | `123` |
+| `plan` | `"gold"` |
+| `project_id` | `456` |
+| `source` | `"gitlab-rails"` |
+| `user_id` | `789`* |
+
+_\* Undergoes a pseudonymization process at the collector level._
+
+These properties [are overriden](https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/tracking/get_standard_context.js)
+with frontend-specific values, like `source` (`gitlab-javascript`), `google_analytics_id`
+and the custom `extra` object. You can modify this object for any subsequent
+structured event that fires, although this is not recommended.
 
 Tracking implementations must have an `action` and a `category`. You can provide additional
 properties from the [structured event taxonomy](index.md#structured-event-taxonomy), in
@@ -396,13 +413,13 @@ Use the following arguments:
 |------------|---------------------------|---------------|-----------------------------------------------------------------------------------------------------------------------------------|
 | `category` | String                    |               | Area or aspect of the application. For example,  `HealthCheckController` or `Lfs::FileTransformer`.                  |
 | `action`   | String                    |               | The action being taken. For example, a controller action such as `create`, or an Active Record callback. |
-| `label`    | String                    | nil           | The specific element or object to act on. This can be one of the following: the label of the element, for example, a tab labeled 'Create from template' for `create_from_template`; a unique identifier if no text is available, for example, `groups_dropdown_close` for closing the Groups dropdown in the top bar; or the name or title attribute of a record being created.                                                          |
-| `property` | String                    | nil           | Any additional property of the element, or object being acted on.                                                          |
-| `value`    | Numeric                   | nil           | Describes a numeric value (decimal) directly related to the event. This could be the value of an input. For example, `10` when clicking `internal` visibility.                                                          |
-| `context`  | Array\[SelfDescribingJSON\] | nil           | An array of custom contexts to send with this event. Most events should not have any custom contexts.                             |
-| `project`  | Project                   | nil           | The project associated with the event. |
-| `user`     | User                      | nil           | The user associated with the event. |
-| `namespace` | Namespace                | nil           | The namespace associated with the event. |
+| `label`    | String                    | `nil`           | The specific element or object to act on. This can be one of the following: the label of the element, for example, a tab labeled 'Create from template' for `create_from_template`; a unique identifier if no text is available, for example, `groups_dropdown_close` for closing the Groups dropdown in the top bar; or the name or title attribute of a record being created.                                                          |
+| `property` | String                    | `nil`           | Any additional property of the element, or object being acted on.                                                          |
+| `value`    | Numeric                   | `nil`           | Describes a numeric value (decimal) directly related to the event. This could be the value of an input. For example, `10` when clicking `internal` visibility.                                                          |
+| `context`  | Array\[SelfDescribingJSON\] | `nil`           | An array of custom contexts to send with this event. Most events should not have any custom contexts.                             |
+| `project`  | Project                   | `nil`           | The project associated with the event. |
+| `user`     | User                      | `nil`           | The user associated with the event. This value undergoes a pseudonymization process at the collector level. |
+| `namespace` | Namespace                | `nil`           | The namespace associated with the event. |
 | `extra`   | Hash                | `{}`         | Additional keyword arguments are collected into a hash and sent with the event. |
 
 ### Unit testing

doc/development/snowplow/index.md

@@ -150,6 +150,23 @@ ORDER BY page_view_start DESC
 LIMIT 100
 ```
 
+#### Top 20 users who fired `reply_comment_button` in the last 30 days
+
+```sql
+SELECT
+  count(*) as hits,
+  se_action,
+  se_category,
+  gsc_pseudonymized_user_id
+FROM legacy.snowplow_gitlab_events_30
+WHERE
+  se_label = 'reply_comment_button'
+  AND gsc_pseudonymized_user_id IS NOT NULL
+GROUP BY gsc_pseudonymized_user_id, se_category, se_action
+ORDER BY count(*) DESC
+LIMIT 20
+```
+
 #### Query JSON formatted data
 
 ```sql

doc/development/snowplow/schemas.md

@@ -10,17 +10,18 @@ This page provides Snowplow schema reference for GitLab events.
 
 ## `gitlab_standard`
 
-We are including the [`gitlab_standard` schema](https://gitlab.com/gitlab-org/iglu/-/blob/master/public/schemas/com.gitlab/gitlab_standard/jsonschema/) with every event. See [Standardize Snowplow Schema](https://gitlab.com/groups/gitlab-org/-/epics/5218) for details.
+We are including the [`gitlab_standard` schema](https://gitlab.com/gitlab-org/iglu/-/blob/master/public/schemas/com.gitlab/gitlab_standard/jsonschema/) for structured events and page views.
 
 The [`StandardContext`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/tracking/standard_context.rb)
-class represents this schema in the application. Some properties are automatically populated for [frontend](https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/views/layouts/_snowplow.html.haml)
-events.
+class represents this schema in the application. Some properties are
+[automatically populated for frontend events](implementation.md#snowplow-javascript-frontend-tracking),
+and can be [provided manually for backend events](implementation.md#implement-ruby-backend-tracking).
 
 | Field Name     | Required            | Default value | Type                  | Description                                                                                 |
 |----------------|:-------------------:|-----------------------|--|---------------------------------------------------------------------------------------------|
 | `project_id`   | **{dotted-circle}** | Current project ID * | integer               |                                                                 |
 | `namespace_id` | **{dotted-circle}** | Current group/namespace ID * | integer               |                                                               |
-| `user_id`      | **{dotted-circle}** | Current user ID * | integer               | User database record ID attribute. This file undergoes a pseudonymization process at the collector level. |
+| `user_id`      | **{dotted-circle}** | Current user ID * | integer               | User database record ID attribute. This value undergoes a pseudonymization process at the collector level. |
 | `context_generated_at` | **{dotted-circle}** | Current timestamp | string (date time format) | Timestamp indicating when context was generated.                                                                |
 | `environment`  | **{check-circle}**  | Current environment | string (max 32 chars) | Name of the source environment, such as `production` or `staging`             |
 | `source`       | **{check-circle}**  | Event source | string (max 32 chars) | Name of the source application, such as  `gitlab-rails` or `gitlab-javascript` |