Document the definition of a "Comment" when it comes to the Importers
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### Problem to solve
Manage:Import frequently gets questions and issues about "missing comments," and the question is usually never answered regarding what kind of comment is missing. Knowing this information up front reduces the time it takes to debug drastically and can help identify where to start. However, people may not know what answer to give or even that there are many kinds of comments.
### Goal
I have prepared the below documentation with the goal being to store it somewhere to help both reporters and the team internally. We will need to verify it's accuracy and then document it.
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:arrow_heading_down: :arrow_heading_down:
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### Types of comments
#### Comments on a diff (Diff Note)
- Is the diff present?
- First ensure that the diff was imported, as importing comments requires this first
- Did the comment happen on the latest version of the diff?
- Comments are only imported against the latest version of a diff
- Was the note outdated with a new diff update? ([fixed in 14.3](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/69977))
- Did the comment in GitHub happen on a diff [that is different](https://gitlab.com/gitlab-org/gitlab/-/issues/343345#note_710950301) from the imported diff in GitLab? ([fixed in 14.5](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/72897))
#### Suggestions (Code formatted comment on a diff)
- Is the diff present?
- First ensure that the diff was imported, as importing comments requires this first
- Did the comment happen on the latest version of the diff?
- Multiple diff versions are not currently supported
- Was the suggestion on a resolved thread? ([fixed in 14.6](https://gitlab.com/gitlab-org/gitlab/-/issues/346638))
- Is the comment actually present but misformatted (fixes in [14.4](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/71411) and [14.5](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/71765))
#### Regular comment (Note)
- Of note, [this import occurs after almost all other steps](https://docs.gitlab.com/ee/development/github_importer.html#8-stageimportnotesworker. Because of this, it is possible they are not imported because a previous step has not finished or has failed.
- Please see other possible reasons listed below
#### Comment within a thread
- Is this comment part of the MR but not within the thread itself? ([fixed in 14.5](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/73595))
#### Other possible reasons
- Are other relations missing?
- Were tags changing while import was running? ([fixed in 14.8](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/80379))
- Are there `GOAWAY` messages in the production.log? (for versions 14.5+, [fixed in 14.8](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/78966))
- Are there more than 40,000 comments that need imported? ([alternative import method released in 14.3](https://gitlab.com/gitlab-org/gitlab/-/issues/332630))
- Is it possible there are some comments missing the submitted_at date from GitHub, for example if this is a [pending](https://docs.github.com/en/rest/reference/pulls#create-a-review-for-a-pull-request) review comment? ([fixed in 14.1](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64645))
- Are there “string contains null byte” errors in the `import_failures` table? ([fixed in 13.12](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61480))
- Are you hitting a [rate limit](https://docs.gitlab.com/ee/administration/raketasks/github_import.html#caveats) or a [secondary rate limit](https://docs.github.com/en/rest/overview/resources-in-the-rest-api#secondary-rate-limits) that could temporarily block you on GitHub? The importer might show as finished in the UI, but the worker has not finished and is actually paused until the rate limit is reset.
issue