v1.2.1: Fix panic in monitor/level_collector (#137)

blip.go

@@ -19,7 +19,7 @@ import (
 	"github.com/aws/aws-sdk-go-v2/aws"
 )
 
-const VERSION = "1.2.0"
+const VERSION = "1.2.1"
 
 var SHA = ""
 

docs/content/about/release-notes.md

@@ -37,6 +37,11 @@ func(metrics []*blip.Metrics) error {
 
 2. If using an integration that works with Blip events, see [event/list.go](https://github.com/cashapp/blip/blob/main/event/list.go) for the new event names.
 
+### v1.2.1 (19 Jul 2024)
+
+* Fixed bug (panic) in `monitor/level_collector` when plan has no levels.
+* Added `plan/default.None`.
+
 ### v1.2.0 (2 Jul 2024)
 
 * Rewrote monitor.Engine ("engine v2") and some of level collector (LCO)

monitor/level_collector.go

@@ -421,7 +421,9 @@ func (c *lco) changePlan(ctx context.Context, doneChan chan struct{}, newState,
 		c.state = newState
 		c.plan = newPlan
 		c.levels = levels
-		c.emr = blip.TimeLimit(0.1, levels[0].Freq, time.Second) // interval minus 10% (max 1s)
+		if len(levels) > 0 { // there can be 0 levels, e.g. plan/default.None
+			c.emr = blip.TimeLimit(0.1, levels[0].Freq, time.Second) // interval minus 10% (max 1s)
+		}
 
 		// Changing state/plan always resumes (if paused); in fact, it's the
 		// only way to resume after Pause is called

plan/default/none.go

@@ -0,0 +1,14 @@
+// Copyright 2024 Block, Inc.
+
+package default_plan
+
+import "github.com/cashapp/blip"
+
+// None returns an empty plan usual for standby instances of Blip.
+func None() blip.Plan {
+	return blip.Plan{
+		Name:   "default-none",
+		Source: "blip",
+		Levels: map[string]blip.Level{},
+	}
+}

plan/sort_test.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/cashapp/blip"
 	"github.com/cashapp/blip/plan"
+	defaultPlan "github.com/cashapp/blip/plan/default"
 )
 
 // --------------------------------------------------------------------------
@@ -471,3 +472,14 @@ func TestSortComplex(t *testing.T) {
 		t.Error(diff)
 	}
 }
+
+func TestSortDefault_None(t *testing.T) {
+	p := defaultPlan.None()
+	gotLevels := plan.Sort(&p)
+	if gotLevels == nil {
+		t.Errorf("got nil sorted levels, execpted non-nil return value")
+	}
+	if len(gotLevels) != 0 {
+		t.Errorf("got %d levels from default.None plan, expected 0", len(gotLevels))
+	}
+}