[interna/sharedcomponent] Use a ring buffer to restrict remembered st…

…atus count (open-telemetry#11826)

#### Description
Use a ring buffer to only remember the last 5 events. This ensures we
remember a reasonable number of events during startup, so that a status
aggregator gets the events for all instances. Then during normal
operation, when we're done adding sources and no longer need to replay
events, we don't have to remember every single event.

#### Link to tracking issue
Closes
open-telemetry#11818

#### Testing

`go test status_test.go -count 1000 -failfast` still passes with many
tries.

.chloggen/fix-sharedcomponent-memory-issue.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: internal/sharedcomponent
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fixed bug where sharedcomponent would use too much memory remembering all the previously reported statuses
+
+# One or more tracking issues or pull requests related to the change
+issues: [11826]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

internal/sharedcomponent/sharedcomponent.go

@@ -7,8 +7,8 @@
 package sharedcomponent // import "go.opentelemetry.io/collector/internal/sharedcomponent"
 
 import (
+	"container/ring"
 	"context"
-	"slices"
 	"sync"
 
 	"go.opentelemetry.io/collector/component"
@@ -77,7 +77,7 @@ func (c *Component[V]) Start(ctx context.Context, host component.Host) error {
 			c.hostWrapper = &hostWrapper{
 				host:           host,
 				sources:        make([]componentstatus.Reporter, 0),
-				previousEvents: make([]*componentstatus.Event, 0),
+				previousEvents: ring.New(5),
 			}
 			statusReporter, isStatusReporter := host.(componentstatus.Reporter)
 			if isStatusReporter {
@@ -110,7 +110,7 @@ var (
 type hostWrapper struct {
 	host           component.Host
 	sources        []componentstatus.Reporter
-	previousEvents []*componentstatus.Event
+	previousEvents *ring.Ring
 	lock           sync.Mutex
 }
 
@@ -122,8 +122,9 @@ func (h *hostWrapper) Report(e *componentstatus.Event) {
 	// Only remember an event if it will be emitted and it has not been sent already.
 	h.lock.Lock()
 	defer h.lock.Unlock()
-	if len(h.sources) > 0 && !slices.Contains(h.previousEvents, e) {
-		h.previousEvents = append(h.previousEvents, e)
+	if len(h.sources) > 0 {
+		h.previousEvents.Value = e
+		h.previousEvents = h.previousEvents.Next()
 	}
 	for _, s := range h.sources {
 		s.Report(e)
@@ -133,9 +134,11 @@ func (h *hostWrapper) Report(e *componentstatus.Event) {
 func (h *hostWrapper) addSource(s componentstatus.Reporter) {
 	h.lock.Lock()
 	defer h.lock.Unlock()
-	for _, e := range h.previousEvents {
-		s.Report(e)
-	}
+	h.previousEvents.Do(func(a any) {
+		if e, ok := a.(*componentstatus.Event); ok {
+			s.Report(e)
+		}
+	})
 	h.sources = append(h.sources, s)
 }