Merge #154416

154416: asim: improve comments for tests under mma r=tbg a=wenyihu6

Epic: CRDB-49117 
Resolves: #154361
Release note: none

---
**asim: rename constraint_satisfaction1 to constraint_satisfaction**

This commit renames constraint_satisfaction1_full_disk.txt to
constraint_satisfaction_full_disk.txt.

---
**asim: improve comments for constraint_satisfaction_full_disk**

This commit improves comments and reduces the test duration for
constraint_satisfaction_full_disk.txt.

---
**asim: delete redundant/not-really-useful tests**

This commit deletes a few redundant or not-really-useful tests.

1. For constraint_satisfaction1, the test sets up a 9-node cluster across 4
   regions (a, b, c, d) with 3, 2, 1, and 3 nodes respectively. It creates 100
   ranges with 5 replicas each, initially placed on stores s1(a), s2(a), s4(b),
   s5(b), and s6(c). The span config requires 2 replicas in region a, 2 in
   region b, and 1 in region c, with lease preferences for region a, so all
   constraints were already satisfied. The generated load was not very
   interesting either.  We will likely need a similar test in the future, but
   this version is removed in favor of writing a better one later.

2. For constraint_satisfaction2, it appears to be leftover setup that used rebalance mode 0
   with other queues disabled, predating the introduction of configurations.

3. For constraint_satisfaction_old_alloc, it also seems to be leftover and is roughly the same as
   constraint_satisfaction1.txt.

4. high_cpu_skewed_placement.txt appears redundant with high_cpu.txt, which also
   uses skewed range placement on s1–3 with load targeting that keyspace. The
   only difference is an additional CPU workload evenly distributed across
   nodes, but it doesn’t test anything meaningfully different. In addition, the test
   set-up was wrong, and the load was hammering only one range.

5. load_distribution_movement_disabled_enable_later.txt was intended to test the
   switch between SMA and MMA mode, but the setup does not create an interesting
   scenario. We will likely need a similar test in the future, but this version
   is removed in favor of writing a better one later.

---
**asim: improve comments for tests under mma**

This test improves the comments on the setup. I’ve made a first pass to clarify
the meaning of various parts, though it may require further review to fully
understand the scenario. This is a starting point.

---
**asim: shorten duration for certain asim tests**

This commit shortens the duration of certain asim tests. Durations were chosen
by looking output plots to identify when there is no more rebalancing activities
or when thrashing patterns remains.

---
**asim: use mib for bytes of gen_ranges**

This commit updates the gen_ranges bytes command to accept values in mib.


Co-authored-by: wenyihu6 <wenyi@cockroachlabs.com>

Author: craig[bot]

pkg/kv/kvserver/asim/tests/datadriven_simulation_test.go

@@ -78,7 +78,7 @@ var runAsimTests = envutil.EnvOrDefaultBool("COCKROACH_RUN_ASIM_TESTS", false)
 //
 //   - "gen_ranges" [ranges=<int>]
 //     [placement_type=(even|skewed|weighted|replica_placement)]
-//     [repl_factor=<int>] [min_key=<int>] [max_key=<int>] [bytes=<int>]
+//     [repl_factor=<int>] [min_key=<int>] [max_key=<int>] [bytes_mib=<int>]
 //     [reset=<bool>]
 //     Initialize the range generator parameters. On the next call to eval, the
 //     range generator is called to assign an ranges and their replica
@@ -285,7 +285,7 @@ func TestDataDriven(t *testing.T) {
 				case "gen_ranges":
 					var ranges, replFactor = 1, 3
 					var minKey, maxKey = int64(0), int64(defaultKeyspace)
-					var bytes int64 = 0
+					var bytesMiB int64 = 0
 					var replace bool
 					var placementTypeStr = "even"
 					buf := strings.Builder{}
@@ -294,7 +294,7 @@ func TestDataDriven(t *testing.T) {
 					scanIfExists(t, d, "placement_type", &placementTypeStr)
 					scanIfExists(t, d, "min_key", &minKey)
 					scanIfExists(t, d, "max_key", &maxKey)
-					scanIfExists(t, d, "bytes", &bytes)
+					scanIfExists(t, d, "bytes_mib", &bytesMiB)
 					scanIfExists(t, d, "replace", &replace)
 
 					placementType := gen.GetRangePlacementType(placementTypeStr)
@@ -310,7 +310,7 @@ func TestDataDriven(t *testing.T) {
 							MinKey:            minKey,
 							MaxKey:            maxKey,
 							ReplicationFactor: replFactor,
-							Bytes:             bytes,
+							Bytes:             bytesMiB << 20,
 							ReplicaPlacement:  replicaPlacement,
 						},
 						PlacementType: placementType,

pkg/kv/kvserver/asim/tests/testdata/non_rand/mma/constraint_satisfaction1.txt

@@ -0,0 +1,62 @@
+# This test verifies that the allocator can satisfy zone constraints when stores
+# have limited disk capacity and replicas need to be rebalanced due to disk
+# fullness. The test sets up a 9-node cluster across 4 regions (a, b, c, d) with
+# 3, 2, 1, and 3 nodes respectively. It creates 10 ranges with 5 replicas each,
+# initially placed only on stores s1, s2, s4, s5, s6 (regions a, b, c). Each store
+# has a 10GB capacity and each range is 500MiB, making stores s1, s2, s4, s5, s6
+# approximately 61% full initially. The span config requires 2 replicas in region
+# a, 2 in region b, and 1 in region c, with lease preferences for region a.
+#
+# Expected outcome: The allocator should rebalance replicas to satisfy the zone
+# constraints while managing disk capacity. Since stores s1 and s2 in region a are
+# initially full, some replicas should move to s3 (also in region a) to maintain
+# the constraint of 2 replicas in region a while reducing disk pressure. Leases
+# should be distributed within region a (s1, s2, s3) due to lease preferences when
+# count-based rebalancing is enabled.
+gen_cluster nodes=9 region=(a,b,c,d) nodes_per_region=(3,2,1,3) store_byte_capacity_gib=10
+----
+
+gen_ranges ranges=10 repl_factor=5 placement_type=replica_placement bytes_mib=500
+{s1,s2,s4,s5,s6}:1
+----
+{s1:*,s2,s4,s5,s6}:1
+
+set_span_config
+[0,9999999999): num_replicas=5 num_voters=5 constraints={'+region=a':2,'+region=b':2,'+region=c':1} lease_preferences=[['+region=a']]
+----
+
+setting split_queue_enabled=false
+----
+
+# TODO(wenyihu6): for mma-only, why didn't we balance more replicas to s3 before stabilizing?
+# TODO(wenyihu6): tests more cases here
+# 1. whats happens if zone config started being satisfied but the full-disk
+# target is against the goal of zone/lease constraints
+# 2. what happens if zone config started being un-satisfied but the full-disk
+# target is against the goal of zone/lease constraints
+# 3. what happens if count-based rebalancing is against any of these goals ^
+
+eval duration=3m samples=1 seed=42 cfgs=(sma-count,mma-count) metrics=(cpu,cpu_util,leases,replicas,disk_fraction_used)
+----
+disk_fraction_used#1: first: [s1=0.61, s2=0.61, s3=0.00, s4=0.61, s5=0.61, s6=0.61, s7=0.00, s8=0.00, s9=0.00] (stddev=0.30, mean=0.34, sum=3)
+disk_fraction_used#1: last:  [s1=0.49, s2=0.37, s3=0.37, s4=0.61, s5=0.61, s6=0.61, s7=0.00, s8=0.00, s9=0.00] (stddev=0.26, mean=0.34, sum=3)
+disk_fraction_used#1: thrash_pct: [s1=48%, s2=26%, s3=0%, s4=0%, s5=0%, s6=0%, s7=0%, s8=0%, s9=0%]  (sum=74%)
+leases#1: first: [s1=10, s2=0, s3=0, s4=0, s5=0, s6=0, s7=0, s8=0, s9=0] (stddev=3.14, mean=1.11, sum=10)
+leases#1: last:  [s1=6, s2=0, s3=4, s4=0, s5=0, s6=0, s7=0, s8=0, s9=0] (stddev=2.13, mean=1.11, sum=10)
+leases#1: thrash_pct: [s1=24%, s2=21%, s3=0%, s4=0%, s5=0%, s6=0%, s7=0%, s8=0%, s9=0%]  (sum=45%)
+replicas#1: first: [s1=10, s2=10, s3=0, s4=10, s5=10, s6=10, s7=0, s8=0, s9=0] (stddev=4.97, mean=5.56, sum=50)
+replicas#1: last:  [s1=8, s2=6, s3=6, s4=10, s5=10, s6=10, s7=0, s8=0, s9=0] (stddev=4.19, mean=5.56, sum=50)
+replicas#1: thrash_pct: [s1=48%, s2=26%, s3=0%, s4=0%, s5=0%, s6=0%, s7=0%, s8=0%, s9=0%]  (sum=74%)
+artifacts[sma-count]: 7ef09084dfb9e631
+==========================
+disk_fraction_used#1: first: [s1=0.61, s2=0.61, s3=0.00, s4=0.61, s5=0.61, s6=0.61, s7=0.00, s8=0.00, s9=0.00] (stddev=0.30, mean=0.34, sum=3)
+disk_fraction_used#1: last:  [s1=0.43, s2=0.43, s3=0.37, s4=0.61, s5=0.61, s6=0.61, s7=0.00, s8=0.00, s9=0.00] (stddev=0.25, mean=0.34, sum=3)
+disk_fraction_used#1: thrash_pct: [s1=72%, s2=72%, s3=0%, s4=0%, s5=0%, s6=0%, s7=0%, s8=0%, s9=0%]  (sum=143%)
+leases#1: first: [s1=10, s2=0, s3=0, s4=0, s5=0, s6=0, s7=0, s8=0, s9=0] (stddev=3.14, mean=1.11, sum=10)
+leases#1: last:  [s1=5, s2=1, s3=4, s4=0, s5=0, s6=0, s7=0, s8=0, s9=0] (stddev=1.85, mean=1.11, sum=10)
+leases#1: thrash_pct: [s1=24%, s2=40%, s3=0%, s4=0%, s5=0%, s6=0%, s7=0%, s8=0%, s9=0%]  (sum=64%)
+replicas#1: first: [s1=10, s2=10, s3=0, s4=10, s5=10, s6=10, s7=0, s8=0, s9=0] (stddev=4.97, mean=5.56, sum=50)
+replicas#1: last:  [s1=7, s2=7, s3=6, s4=10, s5=10, s6=10, s7=0, s8=0, s9=0] (stddev=4.17, mean=5.56, sum=50)
+replicas#1: thrash_pct: [s1=72%, s2=72%, s3=0%, s4=0%, s5=0%, s6=0%, s7=0%, s8=0%, s9=0%]  (sum=143%)
+artifacts[mma-count]: 4874ec1d0424aa31
+==========================