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fix(branching): read last record lsn only after Tenant::gc_cs (#5535)

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Fixes #5531, at least the latest error of not being able to create a
branch from the head under write and gc pressure.
This commit is contained in:
Joonas Koivunen
2023-10-11 18:24:36 +03:00
committed by GitHub
parent 0fc3708de2
commit ddceb9e6cd
1 changed files with 6 additions and 6 deletions
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12
pageserver/src/tenant.rs
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@@ -209,7 +209,7 @@ pub struct Tenant {
/// The remote storage generation, used to protect S3 objects from split-brain.
/// Does not change over the lifetime of the [`Tenant`] object.
///
///
/// This duplicates the generation stored in LocationConf, but that structure is mutable:
/// this copy enforces the invariant that generatio doesn't change during a Tenant's lifetime.
generation: Generation,
@@ -2755,6 +2755,11 @@ impl Tenant {
) -> Result<Arc<Timeline>, CreateTimelineError> {
let src_id = src_timeline.timeline_id;
// First acquire the GC lock so that another task cannot advance the GC
// cutoff in 'gc_info', and make 'start_lsn' invalid, while we are
// creating the branch.
let _gc_cs = self.gc_cs.lock().await;
// If no start LSN is specified, we branch the new timeline from the source timeline's last record LSN
let start_lsn = start_lsn.unwrap_or_else(|| {
let lsn = src_timeline.get_last_record_lsn();
@@ -2762,11 +2767,6 @@ impl Tenant {
lsn
});
// First acquire the GC lock so that another task cannot advance the GC
// cutoff in 'gc_info', and make 'start_lsn' invalid, while we are
// creating the branch.
let _gc_cs = self.gc_cs.lock().await;
// Create a placeholder for the new branch. This will error
// out if the new timeline ID is already in use.
let timeline_uninit_mark = {