[metricbeat] support basepath in beat module

CHANGELOG.next.asciidoc

@@ -405,6 +405,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fix remote_write flaky test. {pull}21173[21173]
 - Remove io.time from windows {pull}22237[22237]
 - Change vsphere.datastore.capacity.used.pct value to betweeen 0 and 1. {pull}23148[23148]
+- `beat` module respects `basepath` config option. {pull}28162[28162]
 
 *Packetbeat*
 

metricbeat/module/beat/beat.go

@@ -21,6 +21,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/url"
+	"path"
+	"strings"
 
 	"github.com/elastic/beats/v7/libbeat/logp"
 	"github.com/elastic/beats/v7/metricbeat/helper"
@@ -35,9 +37,11 @@ func init() {
 	}
 }
 
+var metricSets = []string{"state", "stats"}
+
 // NewModule creates a new module
 func NewModule(base mb.BaseModule) (mb.Module, error) {
-	return elastic.NewModule(&base, []string{"state", "stats"}, logp.NewLogger(ModuleName))
+	return elastic.NewModule(&base, metricSets, logp.NewLogger(ModuleName))
 }
 
 // ModuleName is the name of this module.
@@ -76,7 +80,7 @@ type State struct {
 
 // GetInfo returns the data for the Beat's / endpoint.
 func GetInfo(m *MetricSet) (*Info, error) {
-	content, err := fetchPath(m.HTTP, "/", "")
+	content, err := fetchPath(m.HTTP, "/")
 	if err != nil {
 		return nil, err
 	}
@@ -92,7 +96,7 @@ func GetInfo(m *MetricSet) (*Info, error) {
 
 // GetState returns the data for the Beat's /state endpoint.
 func GetState(m *MetricSet) (*State, error) {
-	content, err := fetchPath(m.HTTP, "/state", "")
+	content, err := fetchPath(m.HTTP, "/state")
 	if err != nil {
 		return nil, err
 	}
@@ -106,16 +110,28 @@ func GetState(m *MetricSet) (*State, error) {
 	return info, nil
 }
 
-func fetchPath(httpHelper *helper.HTTP, path string, query string) ([]byte, error) {
+func fetchPath(httpHelper *helper.HTTP, path string) ([]byte, error) {
 	currentURI := httpHelper.GetURI()
 	defer httpHelper.SetURI(currentURI)
 
 	// Parses the uri to replace the path
-	u, _ := url.Parse(currentURI)
-	u.Path = path
-	u.RawQuery = query
+	u, err := url.Parse(currentURI)
+	if err != nil {
+		return nil, err
+	}
 
-	// Http helper includes the HostData with username and password
-	httpHelper.SetURI(u.String())
+	// HTTP helper includes the HostData with username and password
+	httpHelper.SetURI(fetchURI(u, path))
 	return httpHelper.FetchContent()
 }
+
+func fetchURI(u *url.URL, uriPath string) string {
+	for _, s := range metricSets {
+		if strings.HasSuffix(u.Path, s) {
+			u.Path = u.Path[:len(u.Path)-len(s)]
+			break
+		}
+	}
+	u.Path = path.Join(u.Path, uriPath)
+	return u.String()
+}

metricbeat/module/beat/beat_test.go

@@ -0,0 +1,73 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you under
+// the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package beat
+
+import (
+	"net/url"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"gotest.tools/assert"
+)
+
+func TestFetchURI(t *testing.T) {
+	tcs := []struct {
+		orig, path, want string
+	}{
+		{
+			orig: "https://localhost:5000/some/proxy/path",
+			path: "/state",
+			want: "https://localhost:5000/some/proxy/path/state",
+		}, {
+			orig: "https://localhost:5000/some/proxy/path/state",
+			path: "/state",
+			want: "https://localhost:5000/some/proxy/path/state",
+		}, {
+			orig: "https://localhost:5000/some/proxy/path/state",
+			path: "/",
+			want: "https://localhost:5000/some/proxy/path",
+		}, {
+			orig: "http://localhost:5000",
+			path: "/state",
+			want: "http://localhost:5000/state",
+		}, {
+			orig: "http://localhost:5000/state",
+			path: "/state",
+			want: "http://localhost:5000/state",
+		}, {
+			orig: "http://localhost:5000/stats",
+			path: "/state",
+			want: "http://localhost:5000/state",
+		}, {
+			orig: "http://localhost:5000/stats",
+			path: "/",
+			want: "http://localhost:5000/",
+		}, {
+			orig: "http://localhost:5000/state",
+			path: "/",
+			want: "http://localhost:5000/",
+		},
+	}
+
+	for _, tc := range tcs {
+		u, err := url.Parse(tc.orig)
+		require.NoError(t, err)
+		got := fetchURI(u, tc.path)
+		assert.Equal(t, tc.want, got)
+	}
+}