fix: harden multi-pod delivery and load verification

loadtest/im-pressure/collector.go

@@ -27,6 +27,7 @@ func (n *namedURLs) Set(value string) error {
 
 type metricSnapshot struct {
 	Timestamp time.Time `json:"timestamp"`
+	Phase     string    `json:"phase"`
 	Name      string    `json:"name"`
 	URL       string    `json:"url"`
 	Status    int       `json:"status"`
@@ -35,7 +36,8 @@ type metricSnapshot struct {
 	Error     string    `json:"error,omitempty"`
 }
 
-func runCollector(ctx context.Context, sources namedURLs, output string, interval, duration time.Duration) error {
+func runCollector(ctx context.Context, sources namedURLs, output string, interval, duration time.Duration,
+	coordinatorURL, coordinatorOutput string) error {
 	if len(sources) == 0 {
 		return fmt.Errorf("at least one --url name=url is required")
 	}
@@ -56,8 +58,10 @@ func runCollector(ctx context.Context, sources namedURLs, output string, interva
 	defer writer.Flush()
 	client := &http.Client{Timeout: 10 * time.Second}
 	deadline := time.Now().Add(duration)
+	phase := "before"
 	for {
-		snapshots := collectOnce(ctx, client, sources)
+		phase = detectCollectorPhase(ctx, client, phase, coordinatorURL, coordinatorOutput)
+		snapshots := collectOnce(ctx, client, sources, phase)
 		for _, snapshot := range snapshots {
 			raw, _ := json.Marshal(snapshot)
 			if _, err = writer.Write(append(raw, '\n')); err != nil {
@@ -76,7 +80,36 @@ func runCollector(ctx context.Context, sources namedURLs, output string, interva
 	}
 }
 
-func collectOnce(ctx context.Context, client *http.Client, sources namedURLs) []metricSnapshot {
+func detectCollectorPhase(ctx context.Context, client *http.Client, current, coordinatorURL, coordinatorOutput string) string {
+	if coordinatorOutput != "" {
+		if _, err := os.Stat(coordinatorOutput); err == nil {
+			return "after"
+		}
+	}
+	if coordinatorURL == "" {
+		return current
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet,
+		strings.TrimRight(coordinatorURL, "/")+"/v1/status", nil)
+	if err != nil {
+		return current
+	}
+	response, err := client.Do(req)
+	if err != nil {
+		return current
+	}
+	defer response.Body.Close()
+	var status struct {
+		Start StartInfo `json:"start"`
+	}
+	if response.StatusCode != http.StatusOK || json.NewDecoder(io.LimitReader(response.Body, 1<<20)).Decode(&status) != nil ||
+		status.Start.StartAt.IsZero() || time.Now().Before(status.Start.StartAt) {
+		return current
+	}
+	return "during"
+}
+
+func collectOnce(ctx context.Context, client *http.Client, sources namedURLs, phase string) []metricSnapshot {
 	out := make([]metricSnapshot, len(sources))
 	var wg sync.WaitGroup
 	for i, source := range sources {
@@ -85,7 +118,7 @@ func collectOnce(ctx context.Context, client *http.Client, sources namedURLs) []
 		go func() {
 			defer wg.Done()
 			parts := strings.SplitN(source, "=", 2)
-			snapshot := metricSnapshot{Timestamp: time.Now().UTC(), Name: parts[0], URL: parts[1]}
+			snapshot := metricSnapshot{Timestamp: time.Now().UTC(), Phase: phase, Name: parts[0], URL: parts[1]}
 			started := time.Now()
 			req, err := http.NewRequestWithContext(ctx, http.MethodGet, parts[1], nil)
 			if err == nil {