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refactor(timeline creation): represent bootstrap vs branch using enum (#9366)

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# Problem

Timeline creation can either be bootstrap or branch.
The distinction is made based on whether the `ancestor_*` fields are
present or not.

In the PGDATA import code
(https://github.com/neondatabase/neon/pull/9218), I add a third variant
to timeline creation.

# Solution

The above pushed me to refactor the code in Pageserver to distinguish
the different creation requests through enum variants.

There is no externally observable effect from this change.

On the implementation level, a notable change is that the acquisition of
the `TimelineCreationGuard` happens later than before. This is necessary
so that we have everything in place to construct the
`CreateTimelineIdempotency`. Notably, this moves the acquisition of the
creation guard _after_ the acquisition of the `gc_cs` lock in the case
of branching. This might appear as if we're at risk of holding `gc_cs`
longer than before this PR, but, even before this PR, we were holding
`gc_cs` until after the `wait_completion()` that makes the timeline
creation durable in S3 returns. I don't see any deadlock risk with
reversing the lock acquisition order.

As a drive-by change, I found that the `create_timeline()` function in
`neon_local` is unused, so I removed it.

# Refs

* platform context: https://github.com/neondatabase/neon/pull/9218
* product context: https://github.com/neondatabase/cloud/issues/17507
* next PR stacked atop this one:
https://github.com/neondatabase/neon/pull/9501
This commit is contained in:
Christian Schwarz
2024-10-25 12:04:27 +02:00
committed by GitHub
parent 5069123b6d
commit b782b11b33
7 changed files with 334 additions and 176 deletions
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11
test_runner/fixtures/pageserver/http.py
View File

@@ -476,12 +476,13 @@ class PageserverHttpClient(requests.Session, MetricsGetter):
) -> dict[Any, Any]:
body: dict[str, Any] = {
"new_timeline_id": str(new_timeline_id),
"ancestor_start_lsn": str(ancestor_start_lsn) if ancestor_start_lsn else None,
"ancestor_timeline_id": str(ancestor_timeline_id) if ancestor_timeline_id else None,
"existing_initdb_timeline_id": str(existing_initdb_timeline_id)
if existing_initdb_timeline_id
else None,
}
if ancestor_timeline_id:
body["ancestor_timeline_id"] = str(ancestor_timeline_id)
if ancestor_start_lsn:
body["ancestor_start_lsn"] = str(ancestor_start_lsn)
if existing_initdb_timeline_id:
body["existing_initdb_timeline_id"] = str(existing_initdb_timeline_id)
if pg_version != PgVersion.NOT_SET:
body["pg_version"] = int(pg_version)