Implement new Redis HLL Counters for Work Items

Problem to solve

We need a more scalable redis counter schema for work items that is inclusive of Plan xMAU, Project Management xMAU, and Product Planning xMAU. We cannot aggregate and dedupe events across features within a group or at the stage level with our current redis slot schema.

All three Plan product groups will be using the same base object -- work item. Each product group still needs to track MAU. Is there a better way to approach this given the current constraints and behaviors of our Redis HLL counters?

Proposal

Implement new counter schema
Schema is based on individual actions which are then added to aggregate counters depending on what action was taken and which product groups the xMAU most strongly aligns to.
Use users as a shared redis_slot to allow de-duplication of unique users across all events within Plan. This will allow us to achieve a single, de-duplicated stage-level xMAU while also having the same level of visibility among product groups. If we want to expand to categories, this same pattern would work for that as well.
Once epics have been migrated to work items, remove all legacy Plan xMAU Redis HLL counters.

Acceptance

Service Ping schema approved
~~Add schema to https://docs.gitlab.com/ee/development/work_items.html~~ #362400 (closed)
Implement the first batch of the new counters for the tasks MVC.

Counter Schema for Work Items

Field	Possible Values
`name`	unique, descriptive action name
`category`	most relevant object name to provide context on where the action was taken (ex: `work_item`, `milestone`, `iteration`, `namespace` ...)
`redis_slot`	`users` (when tracking xMAU), `count` (when tracking aggregate action counts)
`aggregation`	`weekly`
`feature_flag`	name of feature flag gating this particular counter (optional)

graph TD
    Event[Specific Interaction Counter] --> AC[Aggregate Counters]
    AC --> Plan[Plan xMAU]
    AC --> PM[Project Management xMAU]
    AC --> PP[Product Planning xMAU]
    AC --> Cer[Certify xMAU]
    AC --> WI[Work Items Users]

Proposed template for issues that need new counters as part of their acceptance criteria:

- **name:** `replace with unique, descriptive action name` 
- **category:** `replace with relevant object name`
- **redis_slot:** `users` 
- **include in the following aggregation counters:**
  - [ ] `xmau_plan`
  - [ ] `xmau_project_management`
  - [ ] `xmau_product_planning`
  - [ ] `xmau_certify`
  - [ ] `users_work_items`
  - [ ] new aggregate counter (name: `replace with name of new aggregate counter here`)
- **documentation:** [Service Ping Implementation](https://docs.gitlab.com/ee/development/service_ping/implement.html), [Redis HLL Counters](https://docs.gitlab.com/ee/development/service_ping/implement.html#redis-hll-counters)

Implementation Steps

See https://docs.gitlab.com/ee/development/service_ping/implement.html and https://docs.gitlab.com/ee/development/service_ping/implement.html#redis-hll-counters

Tasks Example

User creating work item

We will maintain counters for each individual type of interaction on a work item, but we will not segment these interactions by product group. This avoids having to implement and maintain 3x as many counters. We can also track all interactions on a work item by product group in an aggregate counter.

name: users_creating_work_items
category: work_item
redis_slot: users
aggregation: weekly
feature_flag: track_work_items_activity  ## optional

YAML Metric Definition:

key_path: users_creating_work_items
description: Unique users creating work items
product_category: team planning
product_section: dev
product_stage: plan
product_group: group::project management
value_type: number
status: active
milestone: TBD
introduced_by_url: TBD
time_frame: 28d
data_source: redis_hll
distribution:
- ce
- ee
tier:
- free
- premium
- ultimate

User updating work item title

name: users_updating_work_item_title
category: work_item
redis_slot: users
aggregation: weekly
feature_flag: track_work_items_activity  ## optional

YAML Metric Definition:

key_path: users_updating_work_item_title
description: Unique users updating a work item's title
product_category: team planning
product_section: dev
product_stage: plan
product_group: group::project management
value_type: number
status: active
milestone: TBD
introduced_by_url: TBD
time_frame: 28d
data_source: redis_hll
distribution:
- ce
- ee
tier:
- free
- premium
- ultimate

Aggregate counters

Important: Every time a new counter is added, it must also be included in the relevant aggregate counters!

Plan xMAU:

Store in https://gitlab.com/gitlab-org/gitlab/-/blob/master/config/metrics/aggregates/common.yml

- name: xmau_plan
  operator: OR
  source: redis
  time_frame: [7d, 28d]
  events:
    - users_creating_work_items
    - users_updating_work_item_title

YAML Metric Definition:

key_path: xmau_plan
description: Unique users interacting with Plan features
product_category: team planning
product_section: dev
product_stage: plan
product_group: group::project management
value_type: number
status: active
milestone: TBD
introduced_by_url: TBD
time_frame: 28d
data_source: redis_hll
distribution:
- ce
- ee
tier:
- free
- premium
- ultimate

Project Management xMAU:

Store in https://gitlab.com/gitlab-org/gitlab/-/blob/master/config/metrics/aggregates/common.yml

- name: xmau_project_management
  operator: OR
  source: redis
  time_frame: [7d, 28d]
  events:
    - users_creating_work_items
    - users_updating_work_item_title

YAML Metric Definition:

key_path: xmau_project_management
description: Unique users interacting with Project Management features
product_category: team planning
product_section: dev
product_stage: plan
product_group: group::project management
value_type: number
status: active
milestone: TBD
introduced_by_url: TBD
time_frame: 28d
data_source: redis_hll
distribution:
- ce
- ee
tier:
- free
- premium
- ultimate

Work Items Users:

Store in https://gitlab.com/gitlab-org/gitlab/-/blob/master/config/metrics/aggregates/common.yml

- name: users_work_items
  operator: OR
  source: redis
  time_frame: [7d, 28d]
  events:
    - users_creating_work_items
    - users_updating_work_item_title

YAML Metric Definition:

key_path: users_work_items
description: Unique users interacting with work items
product_category: team planning
product_section: dev
product_stage: plan
product_group: group::project management
value_type: number
status: active
milestone: TBD
introduced_by_url: TBD
time_frame: 28d
data_source: redis_hll
distribution:
- ce
- ee
tier:
- free
- premium
- ultimate

Edited May 13, 2022 by Donald Cook