[exporter/loadbalancer] close exporters on shutdown (#36024)

#### Description

I noticed that we don't close the exporters during shutdown. This PR
iterates through the exporters and closes them in a graceful manner.

.chloggen/loadbalancer-exporter-shutdown.yaml

@@ -0,0 +1,27 @@
+# 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. filelogreceiver)
+component: exporter/loadbalancing
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Shutdown exporters during collector shutdown. This fixes a memory leak. 
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [36024]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# 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: []

exporter/loadbalancingexporter/loadbalancer.go

@@ -220,6 +220,10 @@ func endpointFound(endpoint string, endpoints []string) bool {
 func (lb *loadBalancer) Shutdown(ctx context.Context) error {
 	err := lb.res.shutdown(ctx)
 	lb.stopped = true
+
+	for _, e := range lb.exporters {
+		err = errors.Join(err, e.Shutdown(ctx))
+	}
 	return err
 }
 

exporter/loadbalancingexporter/log_exporter_test.go

@@ -302,14 +302,14 @@ func TestConsumeLogs_ConcurrentResolverChange(t *testing.T) {
 	consumeStarted := make(chan struct{})
 	consumeDone := make(chan struct{})
 
-	// imitate a slow exporter
-	te := &mockLogsExporter{Component: mockComponent{}}
-	te.consumelogsfn = func(_ context.Context, _ plog.Logs) error {
-		close(consumeStarted)
-		time.Sleep(50 * time.Millisecond)
-		return te.consumeErr
-	}
 	componentFactory := func(_ context.Context, _ string) (component.Component, error) {
+		// imitate a slow exporter
+		te := &mockLogsExporter{Component: mockComponent{}}
+		te.consumelogsfn = func(_ context.Context, _ plog.Logs) error {
+			close(consumeStarted)
+			time.Sleep(50 * time.Millisecond)
+			return te.consumeErr
+		}
 		return te, nil
 	}
 	lb, err := newLoadBalancer(ts.Logger, simpleConfig(), componentFactory, tb)

exporter/loadbalancingexporter/metrics_exporter_test.go

@@ -553,14 +553,14 @@ func TestConsumeMetrics_ConcurrentResolverChange(t *testing.T) {
 	consumeStarted := make(chan struct{})
 	consumeDone := make(chan struct{})
 
-	// imitate a slow exporter
-	te := &mockMetricsExporter{Component: mockComponent{}}
-	te.ConsumeMetricsFn = func(_ context.Context, _ pmetric.Metrics) error {
-		close(consumeStarted)
-		time.Sleep(50 * time.Millisecond)
-		return te.consumeErr
-	}
 	componentFactory := func(_ context.Context, _ string) (component.Component, error) {
+		// imitate a slow exporter
+		te := &mockMetricsExporter{Component: mockComponent{}}
+		te.ConsumeMetricsFn = func(_ context.Context, _ pmetric.Metrics) error {
+			close(consumeStarted)
+			time.Sleep(50 * time.Millisecond)
+			return te.consumeErr
+		}
 		return te, nil
 	}
 	lb, err := newLoadBalancer(ts.Logger, simpleConfig(), componentFactory, tb)

exporter/loadbalancingexporter/trace_exporter_test.go

@@ -163,13 +163,13 @@ func TestConsumeTraces_ConcurrentResolverChange(t *testing.T) {
 	consumeDone := make(chan struct{})
 
 	// imitate a slow exporter
-	te := &mockTracesExporter{Component: mockComponent{}}
-	te.ConsumeTracesFn = func(_ context.Context, _ ptrace.Traces) error {
-		close(consumeStarted)
-		time.Sleep(50 * time.Millisecond)
-		return te.consumeErr
-	}
 	componentFactory := func(_ context.Context, _ string) (component.Component, error) {
+		te := &mockTracesExporter{Component: mockComponent{}}
+		te.ConsumeTracesFn = func(_ context.Context, _ ptrace.Traces) error {
+			close(consumeStarted)
+			time.Sleep(50 * time.Millisecond)
+			return te.consumeErr
+		}
 		return te, nil
 	}
 	lb, err := newLoadBalancer(ts.Logger, simpleConfig(), componentFactory, tb)