storcon: use attached shard counts for initial shard placement #8061
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c93b2b0 at 2024-06-20T16:15:05.567Z :recycle: |
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## Problem When creating a new shard the storage controller schedules via Scheduler::schedule_shard. This does not take into account the number of attached shards. What it does take into account is the node affinity: when a shard is scheduled, all its nodes (primaries and secondaries) get their affinity incremented. For two node clusters and shards with one secondary we have a pathological case where all primaries are scheduled on the same node. Now that we track the count of attached shards per node, this is trivial to fix. Still, the "proper" fix is to use the pageserver's utilization score. Closes #8041 ## Summary of changes Use attached shard count when deciding which node to schedule a fresh shard on.
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Problem
When creating a new shard the storage controller schedules via Scheduler::schedule_shard. This does not take into account the number of attached shards. What it does take into account is the node affinity: when a shard is scheduled, all its nodes (primaries and secondaries) get their affinity incremented.
For two node clusters and shards with one secondary we have a pathological case where all primaries are scheduled on the same node. Now that we track the count of attached shards per node, this is trivial to fix. Still, the "proper" fix is to use the pageserver's utilization score.
Closes #8041
Summary of changes
Use attached shard count when deciding which node to schedule a fresh shard on.
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