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pageserver: handle multiple attached children in shard resolution (#12336)

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## Problem

When resolving a shard during a split we might have multiple attached
shards with the old shard count (i.e. not all of them are marked in
progress and ignored). Hence, we can compute the desired shard number
based on the old shard count and misroute the request.

## Summary of Changes

Recompute the desired shard every time the shard count changes during
the iteration
This commit is contained in:
Vlad Lazar
2025-06-27 13:46:18 +01:00
committed by GitHub
parent ebc12a388c
commit ebb6e26a64
1 changed files with 16 additions and 7 deletions
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23
pageserver/src/tenant/mgr.rs
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@@ -2200,7 +2200,7 @@ impl TenantManager {
selector: ShardSelector,
) -> ShardResolveResult {
let tenants = self.tenants.read().unwrap();
let mut want_shard = None;
let mut want_shard: Option<ShardIndex> = None;
let mut any_in_progress = None;
match &*tenants {
@@ -2225,14 +2225,23 @@ impl TenantManager {
return ShardResolveResult::Found(tenant.clone());
}
ShardSelector::Page(key) => {
// First slot we see for this tenant, calculate the expected shard number
// for the key: we will use this for checking if this and subsequent
// slots contain the key, rather than recalculating the hash each time.
if want_shard.is_none() {
want_shard = Some(tenant.shard_identity.get_shard_number(&key));
// Each time we find an attached slot with a different shard count,
// recompute the expected shard number: during shard splits we might
// have multiple shards with the old shard count.
if want_shard.is_none()
|| want_shard.unwrap().shard_count != tenant.shard_identity.count
{
want_shard = Some(ShardIndex {
shard_number: tenant.shard_identity.get_shard_number(&key),
shard_count: tenant.shard_identity.count,
});
}
if Some(tenant.shard_identity.number) == want_shard {
if Some(ShardIndex {
shard_number: tenant.shard_identity.number,
shard_count: tenant.shard_identity.count,
}) == want_shard
{
return ShardResolveResult::Found(tenant.clone());
}
}