forgejo/docs/unsure-where-to-put/adr-how-to-trigger-activities.md
2024-04-02 09:03:49 +02:00

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# How to Trigger Activities
- [How to Trigger Activities](#how-to-trigger-activities)
- [Status](#status)
- [Context](#context)
- [Decision](#decision)
- [Choices](#choices)
- [1. Transient Federation without Constraints](#1-transient-federation-without-constraints)
- [Problem - Circularity And Inconsistency](#problem---circularity-and-inconsistency)
- [2. Direct Federation only](#2-direct-federation-only)
- [Discussion for option 2.](#discussion-for-option-2)
- [3. Transient Federation and Remember Processed](#3-transient-federation-and-remember-processed)
- [See also](#see-also)
## Status
Proposal
## Context
While implementing the trigger of federated stars we have to handle the distribution of corresponding Like-Activities to the federated repositories.
This must be done consistently and without circularity, such that a repository starring by a user leads to exactly one added star in every federated repository.
```mermaid
flowchart TD
U(User) -->|Press Star on UI| A(A: repository - follow C by incident)
A ~~~ B(B: follow A)
B ~~~ C(C: follow B)
C ~~~ A
```
## Decision
## Choices
### 1. Transient Federation without Constraints
In this case the star federation process would look like:
1. Repo on an instance receives a star (regardless of whether via UI or federation)
2. Instance federates star to all repos that are set as federated repositories.
#### Problem - Circularity And Inconsistency
Circular federation would lead to a infinite circular distribution of Like-Activities:
```mermaid
flowchart TD
U(User) -->|Press Star on UI| A(A: repository - follow C by incident)
A -->|federate Like Activity| B(B: follow A)
B -->|federate Like Activity| C(C: follow B)
C -->|federate Like Activity| A
```
1. Given a repo on the 3 instances A, B, C.
Repo on instance A has set repo on instance B as federation repo.
Repo on instance B has set repo on instance C as federation repo.
Repo on instance C has set repo on instance A as federation repo.
2. User stars repo on instance A via UI.
3. Instance A sends Like-Activity to repo on instance B.
4. Instance B creates local FederatedUser, stars the repo and sends Like-Activity to repo on instance C.
5. Instance C creates local FederatedUser, stars the repo and sends Like-Activity to repo on instance A.
6. Instance A creates local FederatedUser, since the Actor of the Like-Activity is the local FederatedUser created on instance C.
Thus, the repo on instance A gets another star by this user and sends Like-Activity to the repo on instance C.
7. The circular distribution of Like-Activities continues, since the actor is always the local FederatedUser of the sending instance.
### 2. Direct Federation only
```mermaid
flowchart TD
U(User) -->|Press Star on UI| A(A: repository - follow C not allowed)
A -->|federate Like Activity| B(B: follow A)
A -->|federate Like Activity| C(C: follow B not allowed, has to follow A)
```
In this case the star federation process would look like:
1. Case: Repo on an instance receives a star by an authenticated user via UI/API:
1. Repository gets starred by the authenticated User.
2. Instance federates star to all repos that are set as federated repositories.
2. Case: Repo on an instance receives a star via a Like-Activity:
1. Instance creates FederatedUser and stars the repository.
2. No further star federation to federated repos is triggered.
#### Discussion for option 2.
1. pro
1. Prevent circular communication
2. Clear semantic also in case of "Who should authorize a digital signature"
### 3. Transient Federation and Remember Processed
In this case the star federation process would look like:
1. Repo on an instance receives a star (regardless of whether via UI or federation)
2. If this activity was not operated already in this instance, federate star to all repos that are set as federated repositories.
## See also