Conversation: CommitService::CommitsAreAncestors

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Stages:

• ~"Client Preparation":

• RPC Design: Create Issue

• Server Implementation: Create Issue

• ~"Client Implementation": Create Issue

• ~"Acceptance Testing": Create Issue

RPC Endpoints:

• Endpoint::Name

Known Client Routes:

• Known client endpoints

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Spawned from https://gitlab.com/gitlab-com/infrastructure/issues/2138#note_35962567

The mirror process in GitLab-EE is currently causing an n + 1 issue in Gitaly by calling CommitIsAncestor from within a loop.

Looking at refs_to_delete we may require a bulk version of the CommitIsAncestor method.

Something along the lines of

message CommitsAreAncestorsRequest {
  Repository repository = 1;
  string child_id = 2;
  repeated string ancestor_id = 3;
}

message CommitsAreAncestorsResponse {
  repeated string ancestor_id = 1;
}

service CommitService {
  // Given a list of `ancestor_id` references and a single `child_id`, returns a subset of  
  // `ancestor_id` that are in fact ancestors
  rpc CommitsAreAncestors(CommitsAreAncestorsRequest) returns (CommitsAreAncestorsResponse) {}
}

@jacobvosmaer-gitlab and I discussed this on a call. The first step would be to create a GitLab::Git bulk commits_are_ancestors method (names TBD).

Once this method is created and in use by update_remote_mirror_service, we port the method to Gitaly using the usual process.