asim: add zone config satisfiability check

Now that we have added the option to generate random span configurations in
cockroachdb#110967, we want to have a way to check whether these configurations are
satisfiable with the cluster setting.

This patch adds the validation check. Please note that the validation process can
be expensive with a time complexity of O(max(node count in the cluster, number of
replica constraints, number of voter constraints)). To perform this validation
and see which span config could lead to failure, please use following command:

```
"eval" [verbose=validate]
```

See also: cockroachdb#110967
Part of: cockroachdb#106192
Release Note: none
Epic: none

pkg/BUILD.bazel

@@ -230,6 +230,7 @@ ALL_TESTS = [
     "//pkg/kv/kvserver/asim/state:state_test",
     "//pkg/kv/kvserver/asim/storerebalancer:storerebalancer_test",
     "//pkg/kv/kvserver/asim/tests:tests_test",
+    "//pkg/kv/kvserver/asim/validator:validator_test",
     "//pkg/kv/kvserver/asim/workload:workload_test",
     "//pkg/kv/kvserver/asim:asim_test",
     "//pkg/kv/kvserver/batcheval/result:result_test",
@@ -1412,6 +1413,8 @@ GO_TARGETS = [
     "//pkg/kv/kvserver/asim/storerebalancer:storerebalancer_test",
     "//pkg/kv/kvserver/asim/tests:tests",
     "//pkg/kv/kvserver/asim/tests:tests_test",
+    "//pkg/kv/kvserver/asim/validator:validator",
+    "//pkg/kv/kvserver/asim/validator:validator_test",
     "//pkg/kv/kvserver/asim/workload:workload",
     "//pkg/kv/kvserver/asim/workload:workload_test",
     "//pkg/kv/kvserver/asim:asim",

pkg/kv/kvserver/asim/scheduled/scheduled_event_executor.go

@@ -41,6 +41,8 @@ type EventExecutor interface {
 	// events including details of mutation events, assertion checks, and assertion
 	// results.
 	PrintEventsExecuted() string
+	// ScheduledEvents returns the list of scheduled events.
+	ScheduledEvents() ScheduledEventList
 }
 
 // eventExecutor is the private implementation of the EventExecutor interface,
@@ -71,6 +73,11 @@ func newExecutorWithNoEvents() *eventExecutor {
 	}
 }
 
+// ScheduledEvents returns the list of scheduled events.
+func (e *eventExecutor) ScheduledEvents() ScheduledEventList {
+	return e.scheduledEvents
+}
+
 // PrintEventSummary returns a string summarizing the executed mutation and
 // assertion events.
 func (e *eventExecutor) PrintEventSummary() string {

pkg/kv/kvserver/asim/tests/BUILD.bazel

@@ -20,6 +20,7 @@ go_library(
         "//pkg/kv/kvserver/asim/history",
         "//pkg/kv/kvserver/asim/scheduled",
         "//pkg/kv/kvserver/asim/state",
+        "//pkg/kv/kvserver/asim/validator",
         "//pkg/roachpb",
         "//pkg/sql",
         "//pkg/sql/catalog/catpb",

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

@@ -18,6 +18,8 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/gen"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/history"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/scheduled"
+	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/state"
+	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/validator"
 )
 
 // OutputFlags sets flags for what to output in tests. If you want to add a flag
@@ -39,15 +41,18 @@ const (
 	OutputTopology // 1 << 3: 0000 1000
 	// OutputEvents displays delayed events executed.
 	OutputEvents // 1 << 4: 0001 0000
+	// OutputValidationResult displays validation result of whether any events are
+	// expected to lead to assertion failure.
+	OutputValidationResult // 1 << 5: 0010 0000
 	// OutputAll shows everything above.
-	OutputAll = (1 << (iota - 1)) - 1 // (1 << 5) - 1: 0001 1111
+	OutputAll = (1 << (iota - 1)) - 1 // (1 << 6) - 1: 0011 1111
 )
 
 // ScanFlags converts an array of input strings into a single flag.
 func (o OutputFlags) ScanFlags(inputs []string) OutputFlags {
 	dict := map[string]OutputFlags{"result_only": OutputResultOnly, "test_settings": OutputTestSettings,
 		"initial_state": OutputInitialState, "config_gen": OutputConfigGen, "topology": OutputTopology,
-		"events": OutputEvents, "all": OutputAll}
+		"events": OutputEvents, "validate": OutputValidationResult, "all": OutputAll}
 	flag := OutputResultOnly
 	for _, input := range inputs {
 		flag = flag.set(dict[input])
@@ -169,6 +174,9 @@ func (tr testResultsReport) String() string {
 		if failed || tr.flags.Has(OutputEvents) {
 			buf.WriteString(output.eventExecutor.PrintEventsExecuted())
 		}
+		if failed || tr.flags.Has(OutputValidationResult) {
+			buf.WriteString(validator.Validate(output.initialState, output.eventExecutor))
+		}
 		if failed {
 			buf.WriteString(fmt.Sprintf("sample%d: failed assertion\n%s\n", nthSample, output.reason))
 		} else {

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

@@ -404,7 +404,8 @@ func randomlySelectDataPlacement(randSource *rand.Rand) descpb.DataPlacement {
 // intervals defined by durationToAssert from the start time. These events apply
 // a randomly generated zone configuration followed by an assertion event. Note
 // that these random configurations might be unsatisfiable under the cluster
-// setup.
+// setup. To validate whether the configurations generated are satisfiable,
+// please use "eval" [verbose=validate].
 func generateRandomSurvivalGoalsEvents(
 	regions []state.Region,
 	startTime time.Time,

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

@@ -83,7 +83,8 @@ const (
 //	  4. sum of weights in the array should be equal to 1
 
 // 3. "eval" [seed=<int64>] [num_iterations=<int>] [duration=<time.Duration>]
-// [verbose=(<[]("result_only","test_settings","initial_state","config_gen","event","topology","all")>)]
+// [verbose=(<[]("result_only","test_settings","initial_state","config_gen",
+// "event","topology","validate","all")>)]
 // e.g. eval seed=20 duration=30m2s verbose=(test_settings,initial_state)
 //  - eval: generates a simulation based on the configuration set with the given
 //    commands.

pkg/kv/kvserver/asim/tests/testdata/rand/default_settings

@@ -232,6 +232,8 @@ AU_EAST
   AU_EAST_1
     └── [1 2 3]
 no events were scheduled
+validation result:
+	valid
 sample1: pass
 ----------------------------------
 sample2: start running
@@ -247,6 +249,8 @@ AU_EAST
   AU_EAST_1
     └── [1 2 3]
 no events were scheduled
+validation result:
+	valid
 sample2: pass
 ----------------------------------
 sample3: start running
@@ -262,6 +266,8 @@ AU_EAST
   AU_EAST_1
     └── [1 2 3]
 no events were scheduled
+validation result:
+	valid
 sample3: pass
 ----------------------------------
 

pkg/kv/kvserver/asim/tests/testdata/rand/rand_cluster

@@ -89,6 +89,8 @@ US_West
   US_West_1
     └── [17 18]
 no events were scheduled
+validation result:
+	valid
 sample1: pass
 ----------------------------------
 sample2: start running
@@ -125,6 +127,8 @@ US_West
   US_West_3
     └── [21 22 23 24]
 no events were scheduled
+validation result:
+	valid
 sample2: pass
 ----------------------------------
 sample3: start running
@@ -159,6 +163,8 @@ US_West
   US_West_1
     └── [17 18]
 no events were scheduled
+validation result:
+	valid
 sample3: pass
 ----------------------------------