Introduced sequentialRuleEvalController

Signed-off-by: Marco Pracucci <marco@pracucci.com>

rules/group.go

@@ -71,6 +71,9 @@ type Group struct {
 	// Rule group evaluation iteration function,
 	// defaults to DefaultEvalIterationFunc.
 	evalIterationFunc GroupEvalIterationFunc
+
+	// concurrencyController controls the rules evaluation concurrency.
+	concurrencyController RuleConcurrencyController
 }
 
 // GroupEvalIterationFunc is used to implement and extend rule group
@@ -114,21 +117,27 @@ func NewGroup(o GroupOptions) *Group {
 		evalIterationFunc = DefaultEvalIterationFunc
 	}
 
+	concurrencyController := o.Opts.RuleConcurrencyController
+	if concurrencyController == nil {
+		concurrencyController = sequentialRuleEvalController{}
+	}
+
 	return &Group{
-		name:                 o.Name,
-		file:                 o.File,
-		interval:             o.Interval,
-		limit:                o.Limit,
-		rules:                o.Rules,
-		shouldRestore:        o.ShouldRestore,
-		opts:                 o.Opts,
-		seriesInPreviousEval: make([]map[string]labels.Labels, len(o.Rules)),
-		done:                 make(chan struct{}),
-		managerDone:          o.done,
-		terminated:           make(chan struct{}),
-		logger:               log.With(o.Opts.Logger, "file", o.File, "group", o.Name),
-		metrics:              metrics,
-		evalIterationFunc:    evalIterationFunc,
+		name:                  o.Name,
+		file:                  o.File,
+		interval:              o.Interval,
+		limit:                 o.Limit,
+		rules:                 o.Rules,
+		shouldRestore:         o.ShouldRestore,
+		opts:                  o.Opts,
+		seriesInPreviousEval:  make([]map[string]labels.Labels, len(o.Rules)),
+		done:                  make(chan struct{}),
+		managerDone:           o.done,
+		terminated:            make(chan struct{}),
+		logger:                log.With(o.Opts.Logger, "file", o.File, "group", o.Name),
+		metrics:               metrics,
+		evalIterationFunc:     evalIterationFunc,
+		concurrencyController: concurrencyController,
 	}
 }
 
@@ -570,13 +579,12 @@ func (g *Group) Eval(ctx context.Context, ts time.Time) {
 
 		// If the rule has no dependencies, it can run concurrently because no other rules in this group depend on its output.
 		// Try run concurrently if there are slots available.
-		ctrl := g.opts.RuleConcurrencyController
-		if ctrl != nil && ctrl.RuleEligible(g, rule) && ctrl.Allow() {
+		if ctrl := g.concurrencyController; ctrl.RuleEligible(g, rule) && ctrl.Allow() {
 			wg.Add(1)
 
 			go eval(i, rule, func() {
 				wg.Done()
-				g.opts.RuleConcurrencyController.Done()
+				ctrl.Done()
 			})
 		} else {
 			eval(i, rule, nil)

rules/manager.go

@@ -135,7 +135,11 @@ func NewManager(o *ManagerOptions) *Manager {
 	}
 
 	if o.RuleConcurrencyController == nil {
-		o.RuleConcurrencyController = newRuleConcurrencyController(o.ConcurrentEvalsEnabled, o.MaxConcurrentEvals)
+		if o.ConcurrentEvalsEnabled {
+			o.RuleConcurrencyController = newRuleConcurrencyController(o.MaxConcurrentEvals)
+		} else {
+			o.RuleConcurrencyController = sequentialRuleEvalController{}
+		}
 	}
 
 	m := &Manager{
@@ -184,9 +188,7 @@ func (m *Manager) Update(interval time.Duration, files []string, externalLabels
 	m.mtx.Lock()
 	defer m.mtx.Unlock()
 
-	if m.opts.RuleConcurrencyController != nil {
-		m.opts.RuleConcurrencyController.Invalidate()
-	}
+	m.opts.RuleConcurrencyController.Invalidate()
 
 	groups, errs := m.LoadGroups(interval, externalLabels, externalURL, groupEvalIterationFunc, files...)
 
@@ -436,22 +438,20 @@ type RuleConcurrencyController interface {
 	Invalidate()
 }
 
-func newRuleConcurrencyController(enabled bool, maxConcurrency int64) RuleConcurrencyController {
-	return &concurrentRuleEvalController{
-		enabled: enabled,
-		sema:    semaphore.NewWeighted(maxConcurrency),
-		depMaps: map[*Group]dependencyMap{},
-	}
-}
-
 // concurrentRuleEvalController holds a weighted semaphore which controls the concurrent evaluation of rules.
 type concurrentRuleEvalController struct {
-	enabled   bool
 	sema      *semaphore.Weighted
 	depMapsMu sync.Mutex
 	depMaps   map[*Group]dependencyMap
 }
 
+func newRuleConcurrencyController(maxConcurrency int64) RuleConcurrencyController {
+	return &concurrentRuleEvalController{
+		sema:    semaphore.NewWeighted(maxConcurrency),
+		depMaps: map[*Group]dependencyMap{},
+	}
+}
+
 func (c *concurrentRuleEvalController) RuleEligible(g *Group, r Rule) bool {
 	c.depMapsMu.Lock()
 	defer c.depMapsMu.Unlock()
@@ -466,18 +466,10 @@ func (c *concurrentRuleEvalController) RuleEligible(g *Group, r Rule) bool {
 }
 
 func (c *concurrentRuleEvalController) Allow() bool {
-	if !c.enabled {
-		return false
-	}
-
 	return c.sema.TryAcquire(1)
 }
 
 func (c *concurrentRuleEvalController) Done() {
-	if !c.enabled {
-		return
-	}
-
 	c.sema.Release(1)
 }
 
@@ -488,3 +480,17 @@ func (c *concurrentRuleEvalController) Invalidate() {
 	// Clear out the memoized dependency maps because some or all groups may have been updated.
 	c.depMaps = map[*Group]dependencyMap{}
 }
+
+// sequentialRuleEvalController is a RuleConcurrencyController that runs every rule sequentially.
+type sequentialRuleEvalController struct{}
+
+func (c sequentialRuleEvalController) RuleEligible(_ *Group, _ Rule) bool {
+	return false
+}
+
+func (c sequentialRuleEvalController) Allow() bool {
+	return false
+}
+
+func (c sequentialRuleEvalController) Done()       {}
+func (c sequentialRuleEvalController) Invalidate() {}

rules/manager_test.go

@@ -676,7 +676,8 @@ func TestDeletedRuleMarkedStale(t *testing.T) {
 		rules:                []Rule{},
 		seriesInPreviousEval: []map[string]labels.Labels{},
 		opts: &ManagerOptions{
-			Appendable: st,
+			Appendable:                st,
+			RuleConcurrencyController: sequentialRuleEvalController{},
 		},
 	}
 	newGroup.CopyState(oldGroup)