[Stack Monitoring] Trim Trailing / After Host URI

This removes any trailing slash to simplify configuration of both
Stack Monitoring and AutoOps hostnames.

If the user accidentally adds the `/`, then historically some
requests would succeed and some would fail and, depending on the
error handling, the error may not be made clear. This bypasses the
whole issue.

Author: pickypg

changelog/fragments/1768435100-stack-monitoring-trim-host-trailing-slash.yaml

@@ -0,0 +1,45 @@
+# REQUIRED
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: bug-fix
+
+# REQUIRED for all kinds
+# Change summary; a 80ish characters long description of the change.
+summary: Stack Monitoring now trims trailing slashes from host URLs for simplicity
+
+# REQUIRED for breaking-change, deprecation, known-issue
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+# description:
+
+# REQUIRED for breaking-change, deprecation, known-issue
+# impact:
+
+# REQUIRED for breaking-change, deprecation, known-issue
+# action:
+
+# REQUIRED for all kinds
+# Affected component; usually one of "elastic-agent", "fleet-server", "filebeat", "metricbeat", "auditbeat", "all", etc.
+component: metricbeat
+
+# AUTOMATED
+# OPTIONAL to manually add other PR URLs
+# PR URL: A link the PR that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+# pr: https://github.com/owner/repo/1234
+
+# AUTOMATED
+# OPTIONAL to manually add other issue URLs
+# Issue URL; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+issue: https://github.com/elastic/beats/issues/48426

metricbeat/module/elasticsearch/metricset.go

@@ -86,14 +86,15 @@ type MetricSetAPI interface {
 // management plugin
 type MetricSet struct {
 	mb.BaseMetricSet
+	hostURI     string
 	servicePath string
 	*helper.HTTP
 	Scope        Scope
 	XPackEnabled bool
 }
 
-// NewMetricSet creates an metric set that can be used to build other metric
-// sets that query RabbitMQ management plugin
+// NewMetricSet creates a metric set that can be used to build other metric
+// sets that query Elasticsearch APIs
 func NewMetricSet(base mb.BaseMetricSet, servicePath string) (*MetricSet, error) {
 	http, err := helper.NewHTTP(base)
 	if err != nil {
@@ -131,8 +132,20 @@ func NewMetricSet(base mb.BaseMetricSet, servicePath string) (*MetricSet, error)
 		http.SetHeader("Authorization", "ApiKey "+apiKey)
 	}
 
+	hostURI := base.HostData().SanitizedURI
+
+	// if you supply your URI like "http://localhost:9200/" we need to trim the trailing slash to avoid issues with
+	// downstream paths
+	if strings.HasSuffix(hostURI, "/") {
+		badURI := hostURI
+		hostURI = strings.TrimRight(hostURI, "/")
+
+		base.Logger().Warnf("host URI should not have a trailing slash, updated from %s to %s", badURI, hostURI)
+	}
+
 	ms := &MetricSet{
 		base,
+		hostURI,
 		servicePath,
 		http,
 		config.Scope,
@@ -146,7 +159,7 @@ func NewMetricSet(base mb.BaseMetricSet, servicePath string) (*MetricSet, error)
 
 // GetServiceURI returns the URI of the Elasticsearch service being monitored by this metricset
 func (m *MetricSet) GetServiceURI() string {
-	return m.HostData().SanitizedURI + m.servicePath
+	return m.hostURI + m.servicePath
 }
 
 // SetServiceURI updates the URI of the Elasticsearch service being monitored by this metricset

metricbeat/module/elasticsearch/node/node_test.go

@@ -21,10 +21,11 @@ package node
 
 import (
 	"encoding/base64"
-	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -42,7 +43,7 @@ func TestFetch(t *testing.T) {
 
 	for _, f := range files {
 		t.Run(f, func(t *testing.T) {
-			response, err := ioutil.ReadFile(f)
+			response, err := os.ReadFile(f)
 			require.NoError(t, err)
 
 			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -128,10 +129,17 @@ func TestFetch(t *testing.T) {
 				}))
 				defer server.Close()
 
+				serverURL := server.URL
+
+				// for an arbitrary request, try configuring with an extra trailing slash
+				if strings.HasPrefix(tt.name, "from config") {
+					serverURL = server.URL + "/"
+				}
+
 				config := map[string]any{
 					"module":     "elasticsearch",
 					"metricsets": []string{"node"},
-					"hosts":      []string{server.URL},
+					"hosts":      []string{serverURL},
 				}
 
 				apiKey := base64.StdEncoding.EncodeToString([]byte(tt.apiKey))