Use exit codes (of k6 archive + inspect) as sole indication for initi…

…alization success

1) Introduce an EmptyDir volume for temporary data
This removes the need for any mkdir and avoids writing to the container filesystem,
allowing for e.g. `readOnlyRootFilesystem` security contexts ([1]).

2) Remove all output redirection and grepping for error indicating strings in favor of
using the exit codes from the commands to indicate success or failure.
This approach is much cleaner in regards to any changes to the output of K6 and the vast
space of error there is.

It also reestablishes the clear contract of the `inspect` command to judge the provided
config.

`k6 inspect --execution-requirements` ([2,3]) while also printing warnings or the JSON
should clearly indicate via `err` if there are issues with the provided tests, which
are then converted to a non-zero RC ([4]).

[1] https://kubernetes.io/docs/tasks/configure-pod-container/security-context/
[2] https://github.com/grafana/k6/blob/c212bd277aeedbf8395b917df11bd9be4da490a4/cmd/inspect.go#L34
[3] https://github.com/grafana/k6/blob/c212bd277aeedbf8395b917df11bd9be4da490a4/cmd/inspect.go#L64
[4] https://github.com/grafana/k6/blob/master/cmd/root.go#L90-L118

Fixes: grafana#435

pkg/resources/jobs/initializer.go

@@ -61,31 +61,29 @@ func NewInitializerJob(k6 v1alpha1.TestRunI, argLine string) (*batchv1.Job, erro
 	)
 	istioCommand, istioEnabled := newIstioCommand(k6.GetSpec().Scuttle.Enabled, []string{"sh", "-c"})
 	command := append(istioCommand, fmt.Sprintf(
-		// There can be several scenarios from k6 command here:
-		// a) script is correct and `k6 inspect` outputs JSON
-		// b) script is partially incorrect and `k6` outputs a warning log message and
-		// then a JSON
-		// c) script is incorrect and `k6` outputs an error log message
-		// Warnings at this point are not necessary (warning messages will re-appear in
-		// runner's logs and the user can see them there) so we need a pure JSON here
-		// without any additional messages in cases a) and b). In case c), output should
-		// contain error message and the Job is to exit with non-zero code.
-		//
-		// Due to some pecularities of k6 logging, to achieve the above behaviour,
-		// we need to use a workaround to store all log messages in temp file while
-		// printing JSON as usual. Then parse temp file only for errors, ignoring
-		// any other log messages.
-		// Related: https://github.com/grafana/k6-docs/issues/877
-		"mkdir -p $(dirname %s) && k6 archive %s -O %s %s 2> /tmp/k6logs && k6 inspect --execution-requirements %s 2> /tmp/k6logs ; ! cat /tmp/k6logs | grep 'level=error'",
-		archiveName, scriptName, archiveName, argLine,
-		archiveName))
+		"k6 archive %s -O %s %s && k6 inspect --execution-requirements %s",
+		scriptName, archiveName, argLine, archiveName))
 
 	env := append(newIstioEnvVar(k6.GetSpec().Scuttle, istioEnabled), k6.GetSpec().Initializer.Env...)
 
 	volumes := script.Volume()
+	// emptyDir to hold our temporary data
+	tmpVolume := corev1.Volume{
+		Name: "tmpdir",
+		VolumeSource: corev1.VolumeSource{
+			EmptyDir: &corev1.EmptyDirVolumeSource{},
+		},
+	}
+	volumes = append(volumes, tmpVolume)
 	volumes = append(volumes, k6.GetSpec().Initializer.Volumes...)
 
 	volumeMounts := script.VolumeMount()
+	// make /tmp an EmptyDir
+	tmpVolumeMount := corev1.VolumeMount{
+		Name:      "tmpdir",
+		MountPath: "/tmp",
+	}
+	volumeMounts = append(volumeMounts, tmpVolumeMount)
 	volumeMounts = append(volumeMounts, k6.GetSpec().Initializer.VolumeMounts...)
 
 	var zero32 int32