[opampextension] fix blocking agent shutdown due to unclosed channel (#…

…36754)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

The changes introduced in
#35892
seemed to have introduced some flakyness in the opampsupervisor e2e
tests, as the shutdown of the opamp agent waits for the component health
loop to end. Due to an unclosed channel within the opamp agent however,
the agent does not properly shut down, and the supervisor runs into a
timeout before ultimately sending a SIGKILL to the agent process.
Closing the channel in the Shutdown method of the opamp extension fixes
that and the agent gets shut down properly upon the reception of the
SIGINT signal

#### Link to tracking Issue:

Fixes #36764

#### Testing

This fixes the failing test mentioned in the issue (#36764)

---------

Signed-off-by: Florian Bacher <florian.bacher@dynatrace.com>

.chloggen/opamp-extension-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: opampextension
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix blocking agent shutdown due to unclosed channel
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [36764]
+
+# (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: []

extension/opampextension/opamp_agent.go

@@ -162,6 +162,9 @@ func (o *opampAgent) Shutdown(ctx context.Context) error {
 
 	o.statusSubscriptionWg.Wait()
 	o.componentHealthWg.Wait()
+	if o.componentStatusCh != nil {
+		close(o.componentStatusCh)
+	}
 
 	o.logger.Debug("OpAMP agent shutting down...")
 	if o.opampClient == nil {