add warning and mock output to inspect

Author: fearful-symmetry

internal/pkg/agent/cmd/inspect.go

@@ -181,20 +181,40 @@ func inspectConfig(ctx context.Context, cfgPath string, opts inspectConfigOpts,
 			return fmt.Errorf("failed to get binary mappings: %w", err)
 		}
 
+		// service units like endpoint are special; they require a PID to monitor.
+		// however, `inspect` doesn't talk to the coordinator backend, which means it can't know their actual PID from this point in the code
+		// instead, we look for service units and create a fake PID, so we print the monitoring config anyway.
+		serviceUnitExists := false
+		fakeServicePids := map[string]uint64{}
+
 		// The monitoring config depends on a map from component id to
 		// binary name.
 		binaryMapping := make(map[string]string)
 		for _, component := range components {
 			if spec := component.InputSpec; spec != nil {
 				binaryMapping[component.ID] = component.BinaryName()
+				if spec.Spec.Service != nil {
+					serviceUnitExists = true
+					fakeServicePids[component.ID] = 1234
+				}
 			}
 		}
-		monitorCfg, err := monitorFn(cfg, components, binaryMapping, map[string]uint64{})
+		monitorCfg, err := monitorFn(cfg, components, binaryMapping, fakeServicePids)
 		if err != nil {
 			return fmt.Errorf("failed to get monitoring config: %w", err)
 		}
 
 		if monitorCfg != nil {
+
+			// see above comment; because we don't know endpoint's actual PID, we need to make a fake one. Warn the user.
+			if serviceUnitExists {
+				keys := make([]string, 0, len(fakeServicePids))
+				for k := range fakeServicePids {
+					keys = append(keys, k)
+				}
+				fmt.Fprintf(streams.Err, "WARNING: the inspect command can't accurately produce monitoring configs for service units: %v. Use the diagnostics command to get the real config used for monitoring these components\n", keys)
+			}
+
 			rawCfg := config.MustNewConfigFrom(cfg)
 
 			if err := rawCfg.Merge(monitorCfg); err != nil {
@@ -205,7 +225,9 @@ func inspectConfig(ctx context.Context, cfgPath string, opts inspectConfigOpts,
 			if err != nil {
 				return fmt.Errorf("failed to convert monitoring config: %w", err)
 			}
+
 		}
+
 	}
 
 	return printMapStringConfig(cfg, streams)