From 6520c5a3a1852808b5f99c054f03f9fdef24da68 Mon Sep 17 00:00:00 2001
From: Matt Moyer <moyerm@vmware.com>
Date: Wed, 17 Mar 2021 11:24:59 -0500
Subject: [PATCH] Extend library.DumpLogs() to dump logs from the previous
 container, if one exists.

This is important in case the container has crashed and has been restarted.

Signed-off-by: Matt Moyer <moyerm@vmware.com>
---
 test/library/dumplogs.go | 41 +++++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/test/library/dumplogs.go b/test/library/dumplogs.go
index dca0d276..86dfd252 100644
--- a/test/library/dumplogs.go
+++ b/test/library/dumplogs.go
@@ -6,12 +6,15 @@ package library
 import (
 	"bufio"
 	"context"
+	"fmt"
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/kubernetes"
 )
 
 // DumpLogs is meant to be called in a `defer` to dump the logs of components in the cluster on a test failure.
@@ -25,25 +28,37 @@ func DumpLogs(t *testing.T, namespace string, labelSelector string) {
 	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
 	defer cancel()
 
-	logTailLines := int64(40)
 	pods, err := kubeClient.CoreV1().Pods(namespace).List(ctx, metav1.ListOptions{LabelSelector: labelSelector})
 	require.NoError(t, err)
 
 	for _, pod := range pods.Items {
 		for _, container := range pod.Status.ContainerStatuses {
-			t.Logf("pod %s/%s container %s restarted %d times:", pod.Namespace, pod.Name, container.Name, container.RestartCount)
-			req := kubeClient.CoreV1().Pods(namespace).GetLogs(pod.Name, &corev1.PodLogOptions{
-				Container: container.Name,
-				TailLines: &logTailLines,
-			})
-			logReader, err := req.Stream(ctx)
-			require.NoError(t, err)
-
-			scanner := bufio.NewScanner(logReader)
-			for scanner.Scan() {
-				t.Logf("%s/%s/%s > %s", pod.Namespace, pod.Name, container.Name, scanner.Text())
+			if container.RestartCount > 0 {
+				dumpContainerLogs(ctx, t, kubeClient, pod.Namespace, pod.Name, container.Name, true)
 			}
-			require.NoError(t, scanner.Err())
+			dumpContainerLogs(ctx, t, kubeClient, pod.Namespace, pod.Name, container.Name, false)
 		}
 	}
 }
+
+func dumpContainerLogs(ctx context.Context, t *testing.T, kubeClient kubernetes.Interface, namespace, pod, container string, prev bool) {
+	logTailLines := int64(40)
+	shortName := fmt.Sprintf("%s/%s/%s", namespace, pod, container)
+	logReader, err := kubeClient.CoreV1().Pods(namespace).GetLogs(pod, &corev1.PodLogOptions{
+		Container: container,
+		TailLines: &logTailLines,
+		Previous:  prev,
+	}).Stream(ctx)
+	if !assert.NoErrorf(t, err, "failed to stream logs for container %s", shortName) {
+		return
+	}
+	scanner := bufio.NewScanner(logReader)
+	for scanner.Scan() {
+		prefix := shortName
+		if prev {
+			prefix += " (previous)"
+		}
+		t.Logf("%s > %s", prefix, scanner.Text())
+	}
+	assert.NoError(t, scanner.Err(), "failed to read logs from container %s", shortName)
+}