storcon: change default stripe size to 16 MB (#11168)

## Problem

The current stripe size of 256 MB is a bit large, and can cause load
imbalances across shards. A stripe size of 16 MB appears more reasonable
to avoid hotspots, although we don't see evidence of this in benchmarks.

Resolves https://github.com/neondatabase/cloud/issues/25634.
Touches https://github.com/neondatabase/cloud/issues/21870.

## Summary of changes

* Change the default stripe size to 16 MB.
* Remove `ShardParameters::DEFAULT_STRIPE_SIZE`, and only use
`pageserver_api::shard::DEFAULT_STRIPE_SIZE`.
* Update a bunch of tests that assumed a certain stripe size.

storage_controller/src/compute_hook.rs

@@ -800,7 +800,7 @@ impl ComputeHook {
 
 #[cfg(test)]
 pub(crate) mod tests {
-    use pageserver_api::shard::{ShardCount, ShardNumber};
+    use pageserver_api::shard::{DEFAULT_STRIPE_SIZE, ShardCount, ShardNumber};
     use utils::id::TenantId;
 
     use super::*;
@@ -808,6 +808,7 @@ pub(crate) mod tests {
     #[test]
     fn tenant_updates() -> anyhow::Result<()> {
         let tenant_id = TenantId::generate();
+        let stripe_size = DEFAULT_STRIPE_SIZE;
         let mut tenant_state = ComputeHookTenant::new(
             TenantShardId {
                 tenant_id,
@@ -848,7 +849,7 @@ pub(crate) mod tests {
                 shard_count: ShardCount::new(2),
                 shard_number: ShardNumber(1),
             },
-            stripe_size: ShardStripeSize(32768),
+            stripe_size,
             preferred_az: None,
             node_id: NodeId(1),
         });
@@ -864,7 +865,7 @@ pub(crate) mod tests {
                 shard_count: ShardCount::new(2),
                 shard_number: ShardNumber(0),
             },
-            stripe_size: ShardStripeSize(32768),
+            stripe_size,
             preferred_az: None,
             node_id: NodeId(1),
         });
@@ -874,7 +875,7 @@ pub(crate) mod tests {
             anyhow::bail!("Wrong send result");
         };
         assert_eq!(request.shards.len(), 2);
-        assert_eq!(request.stripe_size, Some(ShardStripeSize(32768)));
+        assert_eq!(request.stripe_size, Some(stripe_size));
 
         // Simulate successful send
         *guard = Some(ComputeRemoteState {

storage_controller/src/service.rs

@@ -43,7 +43,7 @@ use pageserver_api::models::{
     TimelineInfo, TopTenantShardItem, TopTenantShardsRequest,
 };
 use pageserver_api::shard::{
-    ShardCount, ShardIdentity, ShardNumber, ShardStripeSize, TenantShardId,
+    DEFAULT_STRIPE_SIZE, ShardCount, ShardIdentity, ShardNumber, ShardStripeSize, TenantShardId,
 };
 use pageserver_api::upcall_api::{
     ReAttachRequest, ReAttachResponse, ReAttachResponseTenant, ValidateRequest, ValidateResponse,
@@ -2754,7 +2754,7 @@ impl Service {
                         count: tenant_shard_id.shard_count,
                         // We only import un-sharded or single-sharded tenants, so stripe
                         // size can be made up arbitrarily here.
-                        stripe_size: ShardParameters::DEFAULT_STRIPE_SIZE,
+                        stripe_size: DEFAULT_STRIPE_SIZE,
                     },
                     placement_policy: Some(placement_policy),
                     config: req.config.tenant_conf,
@@ -7865,7 +7865,7 @@ impl Service {
         // old, persisted stripe size.
         let new_stripe_size = match candidate.id.shard_count.count() {
             0 => panic!("invalid shard count 0"),
-            1 => Some(ShardParameters::DEFAULT_STRIPE_SIZE),
+            1 => Some(DEFAULT_STRIPE_SIZE),
             2.. => None,
         };
 

storage_controller/src/tenant_shard.rs

@@ -2000,7 +2000,7 @@ pub(crate) mod tests {
     use std::rc::Rc;
 
     use pageserver_api::controller_api::NodeAvailability;
-    use pageserver_api::shard::{ShardCount, ShardNumber};
+    use pageserver_api::shard::{DEFAULT_STRIPE_SIZE, ShardCount, ShardNumber};
     use rand::SeedableRng;
     use rand::rngs::StdRng;
     use utils::id::TenantId;
@@ -2012,6 +2012,7 @@ pub(crate) mod tests {
         let tenant_id = TenantId::generate();
         let shard_number = ShardNumber(0);
         let shard_count = ShardCount::new(1);
+        let stripe_size = DEFAULT_STRIPE_SIZE;
 
         let tenant_shard_id = TenantShardId {
             tenant_id,
@@ -2020,12 +2021,7 @@ pub(crate) mod tests {
         };
         TenantShard::new(
             tenant_shard_id,
-            ShardIdentity::new(
-                shard_number,
-                shard_count,
-                pageserver_api::shard::ShardStripeSize(32768),
-            )
-            .unwrap(),
+            ShardIdentity::new(shard_number, shard_count, stripe_size).unwrap(),
             policy,
             None,
         )
@@ -2045,6 +2041,7 @@ pub(crate) mod tests {
         shard_count: ShardCount,
         preferred_az: Option<AvailabilityZone>,
     ) -> Vec<TenantShard> {
+        let stripe_size = DEFAULT_STRIPE_SIZE;
         (0..shard_count.count())
             .map(|i| {
                 let shard_number = ShardNumber(i);
@@ -2056,12 +2053,7 @@ pub(crate) mod tests {
                 };
                 TenantShard::new(
                     tenant_shard_id,
-                    ShardIdentity::new(
-                        shard_number,
-                        shard_count,
-                        pageserver_api::shard::ShardStripeSize(32768),
-                    )
-                    .unwrap(),
+                    ShardIdentity::new(shard_number, shard_count, stripe_size).unwrap(),
                     policy.clone(),
                     preferred_az.clone(),
                 )