Fix cgroup helper init in add_processor_metadata and `add_docker_me…

…tadata` processors (#41108)

* only initialize cgroup reader once

* docs

* remove old struct fields

---------

Co-authored-by: Pierre HILBERT <pierre.hilbert@elastic.co>

libbeat/processors/add_docker_metadata/add_docker_metadata.go

@@ -47,9 +47,11 @@ const (
 	cgroupCacheExpiration = 5 * time.Minute
 )
 
-// processGroupPaths returns the cgroups associated with a process. This enables
+// initCgroupPaths initializes a new cgroup reader. This enables
 // unit testing by allowing us to stub the OS interface.
-var processCgroupPaths = cgroup.ProcessCgroupPaths
+var initCgroupPaths processors.InitCgroupHandler = func(rootfsMountpoint resolve.Resolver, ignoreRootCgroups bool) (processors.CGReader, error) {
+	return cgroup.NewReader(rootfsMountpoint, ignoreRootCgroups)
+}
 
 func init() {
 	processors.RegisterPlugin(processorName, New)
@@ -61,11 +63,11 @@ type addDockerMetadata struct {
 	fields          []string
 	sourceProcessor beat.Processor
 
-	pidFields       []string         // Field names that contain PIDs.
-	cgroups         *common.Cache    // Cache of PID (int) to cgropus (map[string]string).
-	hostFS          resolve.Resolver // Directory where /proc is found
-	dedot           bool             // If set to true, replace dots in labels with `_`.
-	dockerAvailable bool             // If Docker exists in env, then it is set to true
+	pidFields       []string      // Field names that contain PIDs.
+	cgroups         *common.Cache // Cache of PID (int) to cgropus (map[string]string).
+	dedot           bool          // If set to true, replace dots in labels with `_`.
+	dockerAvailable bool          // If Docker exists in env, then it is set to true
+	cgreader        processors.CGReader
 }
 
 const selector = "add_docker_metadata"
@@ -110,15 +112,20 @@ func buildDockerMetadataProcessor(log *logp.Logger, cfg *conf.C, watcherConstruc
 		}
 	}
 
+	reader, err := initCgroupPaths(resolve.NewTestResolver(config.HostFS), false)
+	if err != nil {
+		return nil, fmt.Errorf("error creating cgroup reader: %w", err)
+	}
+
 	return &addDockerMetadata{
 		log:             log,
 		watcher:         watcher,
 		fields:          config.Fields,
 		sourceProcessor: sourceProcessor,
 		pidFields:       config.MatchPIDs,
-		hostFS:          resolve.NewTestResolver(config.HostFS),
 		dedot:           config.DeDot,
 		dockerAvailable: dockerAvailable,
+		cgreader:        reader,
 	}, nil
 }
 
@@ -277,7 +284,7 @@ func (d *addDockerMetadata) getProcessCgroups(pid int) (cgroup.PathList, error)
 		return cgroups, nil
 	}
 
-	cgroups, err := processCgroupPaths(d.hostFS, pid)
+	cgroups, err := d.cgreader.ProcessCgroupPaths(pid)
 	if err != nil {
 		return cgroups, fmt.Errorf("failed to read cgroups for pid=%v: %w", pid, err)
 	}

libbeat/processors/add_docker_metadata/add_docker_metadata_test.go

@@ -28,6 +28,7 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	"github.com/elastic/beats/v7/libbeat/beat"
+	"github.com/elastic/beats/v7/libbeat/processors"
 	"github.com/elastic/elastic-agent-autodiscover/bus"
 	"github.com/elastic/elastic-agent-autodiscover/docker"
 	"github.com/elastic/elastic-agent-libs/config"
@@ -37,29 +38,35 @@ import (
 	"github.com/elastic/elastic-agent-system-metrics/metric/system/resolve"
 )
 
+type testCGReader struct {
+}
+
+func (r testCGReader) ProcessCgroupPaths(pid int) (cgroup.PathList, error) {
+	switch pid {
+	case 1000:
+		return cgroup.PathList{
+			V1: map[string]cgroup.ControllerPath{
+				"cpu": {ControllerPath: "/docker/8c147fdfab5a2608fe513d10294bf77cb502a231da9725093a155bd25cd1f14b", IsV2: false},
+			},
+		}, nil
+	case 2000:
+		return cgroup.PathList{
+			V1: map[string]cgroup.ControllerPath{
+				"memory": {ControllerPath: "/user.slice", IsV2: false},
+			},
+		}, nil
+	case 3000:
+		// Parser error (hopefully this never happens).
+		return cgroup.PathList{}, fmt.Errorf("cgroup parse failure")
+	default:
+		return cgroup.PathList{}, os.ErrNotExist
+	}
+}
+
 func init() {
 	// Stub out the procfs.
-	processCgroupPaths = func(_ resolve.Resolver, pid int) (cgroup.PathList, error) {
-
-		switch pid {
-		case 1000:
-			return cgroup.PathList{
-				V1: map[string]cgroup.ControllerPath{
-					"cpu": {ControllerPath: "/docker/8c147fdfab5a2608fe513d10294bf77cb502a231da9725093a155bd25cd1f14b", IsV2: false},
-				},
-			}, nil
-		case 2000:
-			return cgroup.PathList{
-				V1: map[string]cgroup.ControllerPath{
-					"memory": {ControllerPath: "/user.slice", IsV2: false},
-				},
-			}, nil
-		case 3000:
-			// Parser error (hopefully this never happens).
-			return cgroup.PathList{}, fmt.Errorf("cgroup parse failure")
-		default:
-			return cgroup.PathList{}, os.ErrNotExist
-		}
+	initCgroupPaths = func(_ resolve.Resolver, _ bool) (processors.CGReader, error) {
+		return testCGReader{}, nil
 	}
 }
 

libbeat/processors/add_process_metadata/add_process_metadata.go

@@ -54,7 +54,10 @@ var (
 
 	procCache = newProcessCache(cacheExpiration, cacheCapacity, cacheEvictionEffort, gosysinfoProvider{})
 
-	processCgroupPaths = cgroup.ProcessCgroupPaths
+	// cgroups resolver, turned to a stub function to make testing easier.
+	initCgroupPaths processors.InitCgroupHandler = func(rootfsMountpoint resolve.Resolver, ignoreRootCgroups bool) (processors.CGReader, error) {
+		return cgroup.NewReader(rootfsMountpoint, ignoreRootCgroups)
+	}
 
 	instanceID atomic.Uint32
 )
@@ -160,6 +163,11 @@ func newProcessMetadataProcessorWithProvider(config config, provider processMeta
 		}
 	}
 
+	reader, err := initCgroupPaths(resolve.NewTestResolver(config.HostPath), false)
+	if err != nil {
+		return nil, fmt.Errorf("error creating cgroup reader: %w", err)
+	}
+
 	// don't use cgroup.ProcessCgroupPaths to save it from doing the work when container id disabled
 	if ok := containsValue(mappings, "container.id"); ok {
 		if withCache && config.CgroupCacheExpireTime != 0 {
@@ -170,9 +178,9 @@ func newProcessMetadataProcessorWithProvider(config config, provider processMeta
 
 			p.cgroupsCache = common.NewCacheWithRemovalListener(config.CgroupCacheExpireTime, 100, evictionListener)
 			p.cgroupsCache.StartJanitor(config.CgroupCacheExpireTime)
-			p.cidProvider = newCidProvider(resolve.NewTestResolver(config.HostPath), config.CgroupPrefixes, config.CgroupRegex, processCgroupPaths, p.cgroupsCache)
+			p.cidProvider = newCidProvider(config.CgroupPrefixes, config.CgroupRegex, reader, p.cgroupsCache)
 		} else {
-			p.cidProvider = newCidProvider(resolve.NewTestResolver(config.HostPath), config.CgroupPrefixes, config.CgroupRegex, processCgroupPaths, nil)
+			p.cidProvider = newCidProvider(config.CgroupPrefixes, config.CgroupRegex, reader, nil)
 		}
 	}
 

libbeat/processors/add_process_metadata/add_process_metadata_test.go

@@ -31,13 +31,28 @@ import (
 
 	"github.com/elastic/beats/v7/libbeat/beat"
 	"github.com/elastic/beats/v7/libbeat/common/capabilities"
+	"github.com/elastic/beats/v7/libbeat/processors"
 	conf "github.com/elastic/elastic-agent-libs/config"
 	"github.com/elastic/elastic-agent-libs/logp"
 	"github.com/elastic/elastic-agent-libs/mapstr"
 	"github.com/elastic/elastic-agent-system-metrics/metric/system/cgroup"
 	"github.com/elastic/elastic-agent-system-metrics/metric/system/resolve"
 )
 
+type testCGRsolver struct {
+	res func(pid int) (cgroup.PathList, error)
+}
+
+func (t testCGRsolver) ProcessCgroupPaths(pid int) (cgroup.PathList, error) {
+	return t.res(pid)
+}
+
+func newCGHandlerBuilder(handler testCGRsolver) processors.InitCgroupHandler {
+	return func(_ resolve.Resolver, _ bool) (processors.CGReader, error) {
+		return handler, nil
+	}
+}
+
 func TestAddProcessMetadata(t *testing.T) {
 	logp.TestingSetup(logp.WithSelectors(processorName))
 
@@ -90,7 +105,7 @@ func TestAddProcessMetadata(t *testing.T) {
 	}
 
 	// mock of the cgroup processCgroupPaths
-	processCgroupPaths = func(_ resolve.Resolver, pid int) (cgroup.PathList, error) {
+	processCgroupPaths := func(pid int) (cgroup.PathList, error) {
 		testMap := map[int]cgroup.PathList{
 			1: {
 				V1: map[string]cgroup.ControllerPath{
@@ -135,6 +150,7 @@ func TestAddProcessMetadata(t *testing.T) {
 
 		return testMap[pid], nil
 	}
+	initCgroupPaths = newCGHandlerBuilder(testCGRsolver{res: processCgroupPaths})
 
 	for _, test := range []struct {
 		description             string
@@ -884,7 +900,7 @@ func TestUsingCache(t *testing.T) {
 	selfPID := os.Getpid()
 
 	// mock of the cgroup processCgroupPaths
-	processCgroupPaths = func(_ resolve.Resolver, pid int) (cgroup.PathList, error) {
+	processCgroupPaths := func(pid int) (cgroup.PathList, error) {
 		testStruct := cgroup.PathList{
 			V1: map[string]cgroup.ControllerPath{
 				"cpu":          {ControllerPath: "/kubepods/besteffort/pod665fb997-575b-11ea-bfce-080027421ddf/b5285682fba7449c86452b89a800609440ecc88a7ba5f2d38bedfb85409b30b1"},
@@ -909,7 +925,7 @@ func TestUsingCache(t *testing.T) {
 		// testMap :=
 		return testMap[pid], nil
 	}
-
+	initCgroupPaths = newCGHandlerBuilder(testCGRsolver{res: processCgroupPaths})
 	config, err := conf.NewConfigFrom(mapstr.M{
 		"match_pids":        []string{"system.process.ppid"},
 		"include_fields":    []string{"container.id", "process.env"},
@@ -1202,15 +1218,17 @@ func TestPIDToInt(t *testing.T) {
 }
 
 func TestV2CID(t *testing.T) {
-	processCgroupPaths = func(_ resolve.Resolver, _ int) (cgroup.PathList, error) {
+	processCgroupPaths := func(_ int) (cgroup.PathList, error) {
 		testMap := cgroup.PathList{
 			V1: map[string]cgroup.ControllerPath{
 				"cpu": {IsV2: true, ControllerPath: "system.slice/docker-2dcbab615aebfa9313feffc5cfdacd381543cfa04c6be3f39ac656e55ef34805.scope"},
 			},
 		}
 		return testMap, nil
 	}
-	provider := newCidProvider(resolve.NewTestResolver(""), nil, defaultCgroupRegex, processCgroupPaths, nil)
+	resolver := testCGRsolver{res: processCgroupPaths}
+	initCgroupPaths = newCGHandlerBuilder(resolver)
+	provider := newCidProvider(nil, defaultCgroupRegex, resolver, nil)
 	result, err := provider.GetCid(1)
 	assert.NoError(t, err)
 	assert.Equal(t, "2dcbab615aebfa9313feffc5cfdacd381543cfa04c6be3f39ac656e55ef34805", result)

libbeat/processors/add_process_metadata/gosigar_cid_provider.go

@@ -26,9 +26,9 @@ import (
 	"strings"
 
 	"github.com/elastic/beats/v7/libbeat/common"
+	"github.com/elastic/beats/v7/libbeat/processors"
 	"github.com/elastic/elastic-agent-libs/logp"
 	"github.com/elastic/elastic-agent-system-metrics/metric/system/cgroup"
-	"github.com/elastic/elastic-agent-system-metrics/metric/system/resolve"
 )
 
 const (
@@ -37,10 +37,9 @@ const (
 
 type gosigarCidProvider struct {
 	log                *logp.Logger
-	hostPath           resolve.Resolver
 	cgroupPrefixes     []string
 	cgroupRegex        *regexp.Regexp
-	processCgroupPaths func(resolve.Resolver, int) (cgroup.PathList, error)
+	processCgroupPaths processors.CGReader
 	pidCidCache        *common.Cache
 }
 
@@ -70,10 +69,9 @@ func (p gosigarCidProvider) GetCid(pid int) (result string, err error) {
 	return cid, nil
 }
 
-func newCidProvider(hostPath resolve.Resolver, cgroupPrefixes []string, cgroupRegex *regexp.Regexp, processCgroupPaths func(resolve.Resolver, int) (cgroup.PathList, error), pidCidCache *common.Cache) gosigarCidProvider {
+func newCidProvider(cgroupPrefixes []string, cgroupRegex *regexp.Regexp, processCgroupPaths processors.CGReader, pidCidCache *common.Cache) gosigarCidProvider {
 	return gosigarCidProvider{
 		log:                logp.NewLogger(providerName),
-		hostPath:           hostPath,
 		cgroupPrefixes:     cgroupPrefixes,
 		cgroupRegex:        cgroupRegex,
 		processCgroupPaths: processCgroupPaths,
@@ -84,7 +82,7 @@ func newCidProvider(hostPath resolve.Resolver, cgroupPrefixes []string, cgroupRe
 // getProcessCgroups returns a mapping of cgroup subsystem name to path. It
 // returns an error if it failed to retrieve the cgroup info.
 func (p gosigarCidProvider) getProcessCgroups(pid int) (cgroup.PathList, error) {
-	pathList, err := p.processCgroupPaths(p.hostPath, pid)
+	pathList, err := p.processCgroupPaths.ProcessCgroupPaths(pid)
 	if err != nil {
 		var pathError *fs.PathError
 		if errors.As(err, &pathError) {

libbeat/processors/cgroups.go

@@ -0,0 +1,32 @@
+// 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 processors
+
+import (
+	"github.com/elastic/elastic-agent-system-metrics/metric/system/cgroup"
+	"github.com/elastic/elastic-agent-system-metrics/metric/system/resolve"
+)
+
+// InitCgroupHandler is a type for creating stubs for the cgroup resolver. Used primarily for testing.
+type InitCgroupHandler = func(rootfsMountpoint resolve.Resolver, ignoreRootCgroups bool) (CGReader, error)
+
+// CGReader wraps the group Reader.ProcessCgroupPaths() call, this allows us to
+// set different cgroups readers for testing.
+type CGReader interface {
+	ProcessCgroupPaths(pid int) (cgroup.PathList, error)
+}