asim: check for LBRebalancingMultiMetric in ShouldRebalanceStore

This commit updates the old store rebalancer's ShouldRebalanceStore to check the
LBRebalancingMultiMetric cluster setting. asim still invokes this method when
checking changes from the old store rebalancer.

Epic: none
Release note: none

Author: wenyihu6

pkg/kv/kvserver/asim/tests/testdata/non_rand/load_distribution_movement_disabled.txt

@@ -63,25 +63,25 @@ last store values: [s1=39, s2=39, s3=39, s4=9, s5=9, s6=9, s7=9, s8=9, s9=9, s10
 
 plot stat=leases
 ----
- 33.00 ┼───────────────╮
- 31.00 ┤               ╰╮
- 29.00 ┤                │
- 27.00 ┤                │
- 25.00 ┤                ╰╮
- 23.00 ┤                 │
- 21.00 ┤                 │
- 19.00 ┤                 │
- 17.00 ┤                 ╰╮
- 15.00 ┤                  │
- 13.00 ┤                  ╭────────────╮
- 11.00 ┤                  │────────────╰───────────────────────────────────────────────
-  9.00 ┤                 ╭╯                             ╰──────────────────────────────
-  7.00 ┤                ╭╯
-  5.00 ┤                │╯              ╭──────────────────────────────────────────────
+ 33.00 ┼───────────────────────────────────────────────────────────────────────────────
+ 31.00 ┤
+ 29.00 ┤
+ 27.00 ┤
+ 25.00 ┤
+ 23.00 ┤
+ 21.00 ┤
+ 19.00 ┤
+ 17.00 ┤
+ 15.00 ┤
+ 13.00 ┤
+ 11.00 ┤
+  9.00 ┤
+  7.00 ┤
+  5.00 ┤
   3.00 ┼───────────────────────────────────────────────────────────────────────────────
                                              leases
 initial store values: [s1=33, s2=3, s3=3, s4=3, s5=3, s6=3, s7=3, s8=3, s9=3, s10=3] (stddev=9.00, mean=6.00, sum=60)
-last store values: [s1=12, s2=10, s3=11, s4=3, s5=5, s6=5, s7=3, s8=3, s9=4, s10=4] (stddev=3.38, mean=6.00, sum=60)
+last store values: [s1=33, s2=3, s3=3, s4=3, s5=3, s6=3, s7=3, s8=3, s9=3, s10=3] (stddev=9.00, mean=6.00, sum=60)
 
 # Next setup a cluster such that there will be imbalanced CPU usage but
 # balanced write load.
@@ -140,22 +140,22 @@ last store values: [s1=39, s2=39, s3=39, s4=9, s5=9, s6=9, s7=9, s8=9, s9=9, s10
 
 plot stat=leases sample=2
 ----
- 33.00 ┼───────────────╮
- 31.00 ┤               ╰╮
- 29.00 ┤                │
- 27.00 ┤                │
- 25.00 ┤                ╰╮
- 23.00 ┤                 │
- 21.00 ┤                 │
- 19.00 ┤                 │
- 17.00 ┤                 ╰╮
- 15.00 ┤                  │
- 13.00 ┤                  ╭────────────╮
- 11.00 ┤                  │────────────╰───────────────────────────────────────────────
-  9.00 ┤                 ╭╯
-  7.00 ┤                ╭╯
-  5.00 ┤                │╯              ╭──────────────────────────────────────────────
+ 33.00 ┼───────────────────────────────────────────────────────────────────────────────
+ 31.00 ┤
+ 29.00 ┤
+ 27.00 ┤
+ 25.00 ┤
+ 23.00 ┤
+ 21.00 ┤
+ 19.00 ┤
+ 17.00 ┤
+ 15.00 ┤
+ 13.00 ┤
+ 11.00 ┤
+  9.00 ┤
+  7.00 ┤
+  5.00 ┤
   3.00 ┼───────────────────────────────────────────────────────────────────────────────
                                              leases
 initial store values: [s1=33, s2=3, s3=3, s4=3, s5=3, s6=3, s7=3, s8=3, s9=3, s10=3] (stddev=9.00, mean=6.00, sum=60)
-last store values: [s1=11, s2=11, s3=11, s4=3, s5=5, s6=5, s7=3, s8=3, s9=4, s10=4] (stddev=3.35, mean=6.00, sum=60)
+last store values: [s1=33, s2=3, s3=3, s4=3, s5=3, s6=3, s7=3, s8=3, s9=3, s10=3] (stddev=9.00, mean=6.00, sum=60)

pkg/kv/kvserver/store_rebalancer.go

@@ -216,7 +216,8 @@ func NewStoreRebalancer(
 			return !rq.store.cfg.SpanConfigSubscriber.LastUpdated().IsEmpty()
 		},
 		disabled: func() bool {
-			return LoadBasedRebalancingMode.Get(&st.SV) == LBRebalancingOff ||
+			mode := LoadBasedRebalancingMode.Get(&st.SV)
+			return mode == LBRebalancingOff || mode == LBRebalancingMultiMetric ||
 				rq.store.cfg.TestingKnobs.DisableStoreRebalancer
 		},
 	}
@@ -503,6 +504,14 @@ func (sr *StoreRebalancer) ShouldRebalanceStore(ctx context.Context, rctx *Rebal
 		return false
 	}
 
+	if !(rctx.mode == LBRebalancingLeasesOnly || rctx.mode == LBRebalancingLeasesAndReplicas) {
+		// There's nothing to do, the store rebalancer is disabled. Note that this
+		// is redundant when called via the store rebalancer's Start method, but
+		// it's necessary when called from tests, which don't start the store
+		// rebalancer loop, such as the asim pkg.
+		return false
+	}
+
 	// We only bother rebalancing stores that are fielding more than the
 	// cluster-level overfull threshold of load.
 	if rctx.LessThanMaxThresholds() {