asim: extract history into its own package

Previously, the history struct (capturing store metrics at each tick and
simulator’s current state) resided within the asim package.

Another PR is introducing assertion registration which enables scheduled
assertion checks to run as delayed events. Since these assertion events use
simulation’s history to conduct assertion checks, the event package would have
to depend on the asim package. However, the asim package would also have to
depend on the event package’s event executor for event ticking, creating a
circular dependency.

To address this issue, this patch moves the history component out of the asim
package to its own package.

Note that this commit does not change any existing behavior, and the main
purpose is to make future commits cleaner.

See also: cockroachdb#109316
Part of: cockroachdb#106192
Release note: none

pkg/BUILD.bazel

@@ -1305,6 +1305,7 @@ GO_TARGETS = [
     "//pkg/kv/kvserver/asim/gen:gen",
     "//pkg/kv/kvserver/asim/gossip:gossip",
     "//pkg/kv/kvserver/asim/gossip:gossip_test",
+    "//pkg/kv/kvserver/asim/history:history",
     "//pkg/kv/kvserver/asim/metrics:metrics",
     "//pkg/kv/kvserver/asim/metrics:metrics_test",
     "//pkg/kv/kvserver/asim/op:op",

pkg/kv/kvserver/asim/BUILD.bazel

@@ -9,6 +9,7 @@ go_library(
         "//pkg/kv/kvserver/asim/config",
         "//pkg/kv/kvserver/asim/event",
         "//pkg/kv/kvserver/asim/gossip",
+        "//pkg/kv/kvserver/asim/history",
         "//pkg/kv/kvserver/asim/metrics",
         "//pkg/kv/kvserver/asim/op",
         "//pkg/kv/kvserver/asim/queue",
@@ -26,6 +27,7 @@ go_test(
     deps = [
         ":asim",
         "//pkg/kv/kvserver/asim/config",
+        "//pkg/kv/kvserver/asim/history",
         "//pkg/kv/kvserver/asim/metrics",
         "//pkg/kv/kvserver/asim/state",
         "//pkg/kv/kvserver/asim/workload",

pkg/kv/kvserver/asim/asim.go

@@ -17,6 +17,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/config"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/event"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/gossip"
+	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/history"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/metrics"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/op"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/queue"
@@ -60,7 +61,7 @@ type Simulator struct {
 	settings *config.SimulationSettings
 
 	metrics *metrics.Tracker
-	history History
+	history history.History
 }
 
 func (s *Simulator) Curr() time.Time {
@@ -71,19 +72,6 @@ func (s *Simulator) State() state.State {
 	return s.state
 }
 
-// History contains recorded information that summarizes a simulation run.
-// Currently it only contains the store metrics of the run.
-// TODO(kvoli): Add a range log like structure to the history.
-type History struct {
-	Recorded [][]metrics.StoreMetrics
-	S        state.State
-}
-
-// Listen implements the metrics.StoreMetricListener interface.
-func (h *History) Listen(ctx context.Context, sms []metrics.StoreMetrics) {
-	h.Recorded = append(h.Recorded, sms)
-}
-
 // NewSimulator constructs a valid Simulator.
 func NewSimulator(
 	duration time.Duration,
@@ -118,7 +106,7 @@ func NewSimulator(
 		shuffler:       state.NewShuffler(settings.Seed),
 		// TODO(kvoli): Keeping the state around is a bit hacky, find a better
 		// method of reporting the ranges.
-		history:  History{Recorded: [][]metrics.StoreMetrics{}, S: initialState},
+		history:  history.History{Recorded: [][]metrics.StoreMetrics{}, S: initialState},
 		events:   events,
 		settings: settings,
 	}
@@ -190,7 +178,7 @@ func (s *Simulator) GetNextTickTime() (done bool, tick time.Time) {
 
 // History returns the current recorded history of a simulation run. Calling
 // this on a Simulator that has not begun will return an empty history.
-func (s *Simulator) History() History {
+func (s *Simulator) History() history.History {
 	return s.history
 }
 

pkg/kv/kvserver/asim/asim_test.go

@@ -18,6 +18,7 @@ import (
 
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/config"
+	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/history"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/metrics"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/state"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/workload"
@@ -57,7 +58,7 @@ func TestAsimDeterministic(t *testing.T) {
 	// be larger than 3 keys per range.
 	keyspace := 3 * ranges
 	// Track the run to compare against for determinism.
-	var refRun asim.History
+	var refRun history.History
 
 	for run := 0; run < runs; run++ {
 		rwg := make([]workload.Generator, 1)

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

@@ -0,0 +1,12 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "history",
+    srcs = ["history.go"],
+    importpath = "github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/history",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/kv/kvserver/asim/metrics",
+        "//pkg/kv/kvserver/asim/state",
+    ],
+)

pkg/kv/kvserver/asim/history/history.go

@@ -0,0 +1,31 @@
+// Copyright 2022 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package history
+
+import (
+	"context"
+
+	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/metrics"
+	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/state"
+)
+
+// History contains recorded information that summarizes a simulation run.
+// Currently it only contains the store metrics of the run.
+// TODO(kvoli): Add a range log like structure to the history.
+type History struct {
+	Recorded [][]metrics.StoreMetrics
+	S        state.State
+}
+
+// Listen implements the metrics.StoreMetricListener interface.
+func (h *History) Listen(ctx context.Context, sms []metrics.StoreMetrics) {
+	h.Recorded = append(h.Recorded, sms)
+}

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

@@ -12,10 +12,10 @@ go_test(
     embed = [":tests"],
     deps = [
         "//pkg/kv/kvserver/allocator/allocatorimpl",
-        "//pkg/kv/kvserver/asim",
         "//pkg/kv/kvserver/asim/config",
         "//pkg/kv/kvserver/asim/event",
         "//pkg/kv/kvserver/asim/gen",
+        "//pkg/kv/kvserver/asim/history",
         "//pkg/kv/kvserver/asim/metrics",
         "//pkg/kv/kvserver/asim/state",
         "//pkg/kv/kvserver/liveness/livenesspb",
@@ -41,10 +41,10 @@ go_library(
     importpath = "github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/tests",
     visibility = ["//visibility:public"],
     deps = [
-        "//pkg/kv/kvserver/asim",
         "//pkg/kv/kvserver/asim/config",
         "//pkg/kv/kvserver/asim/event",
         "//pkg/kv/kvserver/asim/gen",
+        "//pkg/kv/kvserver/asim/history",
         "//pkg/kv/kvserver/asim/metrics",
         "//pkg/kv/kvserver/asim/state",
         "//pkg/roachpb",

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

@@ -16,7 +16,7 @@ import (
 	"math"
 	"strings"
 
-	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim"
+	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/history"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/metrics"
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/spanconfig/spanconfigtestutils"
@@ -83,7 +83,7 @@ type SimulationAssertion interface {
 	// Assert looks at a simulation run history and returns true if the
 	// assertion holds and false if not. When the assertion does not hold, the
 	// reason is also returned.
-	Assert(context.Context, asim.History) (holds bool, reason string)
+	Assert(context.Context, history.History) (holds bool, reason string)
 	// String returns the string representation of the assertion.
 	String() string
 }
@@ -107,7 +107,7 @@ type steadyStateAssertion struct {
 // assertion tick. If violated, holds is returned as false along with the
 // reason.
 func (sa steadyStateAssertion) Assert(
-	ctx context.Context, h asim.History,
+	ctx context.Context, h history.History,
 ) (holds bool, reason string) {
 	m := h.Recorded
 	ticks := len(m)
@@ -193,7 +193,9 @@ type balanceAssertion struct {
 // stat's maximum/mean (over all stores) in the cluster meets the threshold
 // constraint at each assertion tick. If violated, holds is returned as false
 // along with the reason.
-func (ba balanceAssertion) Assert(ctx context.Context, h asim.History) (holds bool, reason string) {
+func (ba balanceAssertion) Assert(
+	ctx context.Context, h history.History,
+) (holds bool, reason string) {
 	m := h.Recorded
 	ticks := len(m)
 	if ba.ticks > ticks {
@@ -255,7 +257,7 @@ type storeStatAssertion struct {
 // assertion holds and false if not. When the assertion does not hold, the
 // reason is also returned.
 func (sa storeStatAssertion) Assert(
-	ctx context.Context, h asim.History,
+	ctx context.Context, h history.History,
 ) (holds bool, reason string) {
 	m := h.Recorded
 	ticks := len(m)
@@ -313,7 +315,7 @@ const conformanceAssertionSentinel = -1
 // assertion holds and false if not. When the assertion does not hold, the
 // reason is also returned.
 func (ca conformanceAssertion) Assert(
-	ctx context.Context, h asim.History,
+	ctx context.Context, h history.History,
 ) (holds bool, reason string) {
 	report := h.S.Report()
 	buf := strings.Builder{}

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

@@ -19,10 +19,10 @@ import (
 	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/allocator/allocatorimpl"
-	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/config"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/event"
 	"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/metrics"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/state"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/liveness/livenesspb"
@@ -171,7 +171,7 @@ func TestDataDriven(t *testing.T) {
 		settingsGen := gen.StaticSettings{Settings: config.DefaultSimulationSettings()}
 		eventGen := gen.StaticEvents{DelayedEvents: event.DelayedEventList{}}
 		assertions := []SimulationAssertion{}
-		runs := []asim.History{}
+		runs := []history.History{}
 		datadriven.RunTest(t, path, func(t *testing.T, d *datadriven.TestData) string {
 			switch d.Cmd {
 			case "gen_load":

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

@@ -18,8 +18,8 @@ import (
 	"strings"
 	"time"
 
-	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim"
 	"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/state"
 )
 
@@ -167,7 +167,7 @@ func loadClusterInfo(configName string) gen.LoadedCluster {
 // checkAssertions checks the given history and assertions, returning (bool,
 // reason) indicating any failures and reasons if any assertions fail.
 func checkAssertions(
-	ctx context.Context, history asim.History, assertions []SimulationAssertion,
+	ctx context.Context, history history.History, assertions []SimulationAssertion,
 ) (bool, string) {
 	assertionFailures := []string{}
 	failureExists := false