76 lines
2.8 KiB
Markdown
76 lines
2.8 KiB
Markdown
# How to Trigger Activities
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## Status
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Proposal
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## Context
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While implementing the trigger of federated stars we have to handle the distribution of corresponding Like-Activities to the federated repositories.
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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.
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```mermaid
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flowchart TD
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U(User) -->|Press Star on UI| A(A: repository - follow C by incident)
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A ~~~ B(B: follow A)
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B ~~~ C(C: follow B)
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C ~~~ A
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```
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## Decision
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## Choices
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### 1. Transient Federation
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In this case the star federation process would look like:
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1. Repo on an instance receives a star (regardless of whether via UI or federation)
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2. Instance federates star to all repos that are set as federated repositories.
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#### Problem - Circularity And Inconsistency
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Circular federation would lead to a infinite circular distribution of Like-Activities:
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```mermaid
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flowchart TD
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U(User) -->|Press Star on UI| A(A: repository - follow C by incident)
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A -->|federate Like Activity| B(B: follow A)
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B -->|federate Like Activity| C(C: follow B)
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C -->|federate Like Activity| A
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```
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1. Given a repo on the 3 instances A, B, C.
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Repo on instance A has set repo on instance B as federation repo.
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Repo on instance B has set repo on instance C as federation repo.
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Repo on instance C has set repo on instance A as federation repo.
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2. User stars repo on instance A via UI.
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3. Instance A sends Like-Activity to repo on instance B.
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4. Instance B creates local FederatedUser, stars the repo and sends Like-Activity to repo on instance C.
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5. Instance C creates local FederatedUser, stars the repo and sends Like-Activity to repo on instance A.
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6. Instance A creates local FederatedUser, since the Actor of the Like-Activity is the local FederatedUser created on instance C.
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Thus, the repo on instance A gets another star by this user and sends Like-Activity to the repo on instance C.
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7. The circular distribution of Like-Activities continues, since the actor is always the local FederatedUser of the sending instance.
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### 2. Direct Federation
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```mermaid
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flowchart TD
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U(User) -->|Press Star on UI| A(A: repository - follow C not allowed)
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A -->|federate Like Activity| B(B: follow A)
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A -->|federate Like Activity| C(C: follow B not allowed, has to follow A)
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```
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In this case the star federation process would look like:
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1. Case: Repo on an instance receives a star by an authenticated user via UI/API:
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1. Repository gets starred by the authenticated User.
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2. Instance federates star to all repos that are set as federated repositories.
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2. Case: Repo on an instance receives a star via a Like-Activity:
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1. Instance creates FederatedUser and stars the repository.
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2. No further star federation to federated repos is triggered.
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## See also
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