Added basic logstash verification

Add a test to make sure that Logstash is running, by testing the metrics API endpoint
and checking that the value of status is "green"

docs/reference/api-docs.asciidoc

@@ -1876,7 +1876,7 @@ LogstashSpec defines the desired state of Logstash
 | *`image`* __string__ | Image is the Logstash Docker image to deploy. Version and Type have to match the Logstash in the image.
 | *`config`* __xref:{anchor_prefix}-github-com-elastic-cloud-on-k8s-v2-pkg-apis-common-v1-config[$$Config$$]__ | Config holds the Logstash configuration. At most one of [`Config`, `ConfigRef`] can be specified.
 | *`configRef`* __xref:{anchor_prefix}-github-com-elastic-cloud-on-k8s-v2-pkg-apis-common-v1-configsource[$$ConfigSource$$]__ | ConfigRef contains a reference to an existing Kubernetes Secret holding the Logstash configuration. Logstash settings must be specified as yaml, under a single "logstash.yml" entry. At most one of [`Config`, `ConfigRef`] can be specified.
-| *`http`* __xref:{anchor_prefix}-github-com-elastic-cloud-on-k8s-v2-pkg-apis-common-v1-httpconfig[$$HTTPConfig$$]__ | HTTP holds the HTTP layer configuration for the Logstash Metrics API
+| *`http`* __xref:{anchor_prefix}-github-com-elastic-cloud-on-k8s-v2-pkg-apis-common-v1-httpconfig[$$HTTPConfig$$]__ | HTTP holds the HTTP layer configuration for the Logstash Metrics API TODO: This should likely be changed to a more general `Services LogstashService[]`, where `LogstashService` looks       a lot like `HTTPConfig`, but is applicable for more than just an HTTP endpoint, as logstash may need to       be opened up for other services: beats, TCP, UDP, etc, inputs
 | *`podTemplate`* __link:https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.20/#podtemplatespec-v1-core[$$PodTemplateSpec$$]__ | PodTemplate provides customisation options for the Logstash pods.
 | *`revisionHistoryLimit`* __integer__ | RevisionHistoryLimit is the number of revisions to retain to allow rollback in the underlying StatefulSet.
 | *`secureSettings`* __xref:{anchor_prefix}-github-com-elastic-cloud-on-k8s-v2-pkg-apis-common-v1-secretsource[$$SecretSource$$] array__ | SecureSettings is a list of references to Kubernetes Secrets containing sensitive configuration options for the Logstash. Secrets data can be then referenced in the Logstash config using the Secret's keys or as specified in `Entries` field of each SecureSetting.

test/e2e/test/logstash/checks.go

@@ -6,13 +6,19 @@ package logstash
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 
 	logstashv1alpha1 "github.com/elastic/cloud-on-k8s/v2/pkg/apis/logstash/v1alpha1"
 	"github.com/elastic/cloud-on-k8s/v2/pkg/utils/k8s"
 	"github.com/elastic/cloud-on-k8s/v2/test/e2e/test"
 )
 
+type logstashStatus struct {
+	Version string `json:"version"`
+	Status  string `json:"status"`
+}
+
 // CheckSecrets checks that expected secrets have been created.
 func CheckSecrets(b Builder, k *test.K8sClient) test.Step {
 	return test.CheckSecretsContent(k, b.Logstash.Namespace, func() []test.ExpectedSecret {
@@ -58,6 +64,28 @@ func CheckStatus(b Builder, k *test.K8sClient) test.Step {
 
 func (b Builder) CheckStackTestSteps(k *test.K8sClient) test.StepList {
 	println(test.Ctx().TestTimeout)
-	// TODO: Add stack checks
-	return test.StepList{}
+	return test.StepList{
+		{
+			Name: "Logstash should respond to requests",
+			Test: test.Eventually(func() error {
+				client, err := NewLogstashClient(b.Logstash, k)
+				if err != nil {
+					return err
+				}
+				bytes, err := DoRequest(client, b.Logstash, "GET", "/")
+				if err != nil {
+					return err
+				}
+				var status logstashStatus
+				if err := json.Unmarshal(bytes, &status); err != nil {
+					return err
+				}
+
+				if status.Status != "green" {
+					return fmt.Errorf("expected green but got %s", status.Status)
+				}
+				return nil
+			}),
+		},
+	}
 }

test/e2e/test/logstash/http_client.go

@@ -0,0 +1,67 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License 2.0;
+// you may not use this file except in compliance with the Elastic License 2.0.
+
+package logstash
+
+import (
+	"context"
+	"crypto/x509"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+
+	"github.com/elastic/cloud-on-k8s/v2/pkg/apis/logstash/v1alpha1"
+	// "github.com/elastic/cloud-on-k8s/v2/pkg/controller/logstash"
+	"github.com/elastic/cloud-on-k8s/v2/test/e2e/test"
+)
+
+type APIError struct {
+	StatusCode int
+	msg        string
+}
+
+func (e *APIError) Error() string {
+	return e.msg
+}
+
+// TODO refactor identical to Kibana client
+func NewLogstashClient(logstash v1alpha1.Logstash, k *test.K8sClient) (*http.Client, error) {
+	var caCerts []*x509.Certificate
+	// if ems.Spec.HTTP.TLS.Enabled() {
+	//	crts, err := k.GetHTTPCerts(maps.EMSNamer, ems.Namespace, ems.Name)
+	//	if err != nil {
+	//		return nil, err
+	//	}
+	//	caCerts = crts
+	//}
+	return test.NewHTTPClient(caCerts), nil
+}
+
+func DoRequest(client *http.Client, logstash v1alpha1.Logstash, method, path string) ([]byte, error) {
+	scheme := "http"
+
+	url, err := url.Parse(fmt.Sprintf("%s://%s.%s.svc:9600%s", scheme, v1alpha1.HTTPServiceName(logstash.Name), logstash.Namespace, path))
+	if err != nil {
+		return nil, fmt.Errorf("while parsing URL: %w", err)
+	}
+
+	request, err := http.NewRequestWithContext(context.Background(), method, url.String(), nil)
+	if err != nil {
+		return nil, fmt.Errorf("while constructing request: %w", err)
+	}
+
+	resp, err := client.Do(request)
+	if err != nil {
+		return nil, fmt.Errorf("while making request: %w", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode < 200 || resp.StatusCode > 299 {
+		return nil, &APIError{
+			StatusCode: resp.StatusCode,
+			msg:        fmt.Sprintf("fail to request %s, status is %d)", path, resp.StatusCode),
+		}
+	}
+	return io.ReadAll(resp.Body)
+}