[component] clarifying lifecycle expectation

.chloggen/msg_update-docs-for-component.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: component.Component
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Clarifying expectations on the component lifecycle.
+
+# One or more tracking issues or pull requests related to the change
+issues: [6507]
+
+# (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:

component/component.go

@@ -57,6 +57,10 @@ type Component interface {
 	// Shutdown is invoked during service shutdown. After Shutdown() is called, if the component
 	// accepted data in any way, it should not accept it anymore.
 	//
+	// This method must be safe to call:
+	//   - without Start() having been called
+	//   - if the component is in a shutdown state already
+	//
 	// If there are any background operations running by the component they must be aborted before
 	// this function returns. Remember that if you started any long-running background operations from
 	// the Start() method, those operations must be also cancelled. If there are any buffers in the