[observer/cfgarden] New component (#33727)

**Description:** 
We would like to implement a new observer for
[Cloudfoundry](https://www.cloudfoundry.org/) containers/applications.
The idea is not make use of the main API but the local one, which is
available as unix socket on each node and manages the containers
lifecycle. The main API would remain as optional and only to get
Application info (which only involves one GET http request once the app
id is known).


**Link to tracking Issue:**
[33618](#33618)

**Testing:** First component PR

**Documentation:** Added Readme

---------

Co-authored-by: Tomás Mota <tomas.mota@springernature.com>
Co-authored-by: Jose Riguera <jose.riguera@springer.com>
Co-authored-by: Tomás Mota <tomasmota@hey.com>
Co-authored-by: Curtis Robert <crobert@splunk.com>
Co-authored-by: José Riguera Lopez <jriguera@gmail.com>

.chloggen/add-cfgardenobserver.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: new_component
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: extensions/observer/cfgardenobserver
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add a new observer that discovers containers through the Garden API
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [33618]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

.github/CODEOWNERS

@@ -103,6 +103,7 @@ extension/httpforwarderextension/                                   @open-teleme
 extension/jaegerremotesampling/                                     @open-telemetry/collector-contrib-approvers @yurishkuro @frzifus
 extension/oauth2clientauthextension/                                @open-telemetry/collector-contrib-approvers @pavankrish123 @jpkrohling
 extension/observer/                                                 @open-telemetry/collector-contrib-approvers @dmitryax @rmfitzpatrick
+extension/observer/cfgardenobserver/                                @open-telemetry/collector-contrib-approvers @cemdk @tomasmota @m1rp @jriguera @crobert-1
 extension/observer/dockerobserver/                                  @open-telemetry/collector-contrib-approvers @MovieStoreGuy
 extension/observer/ecsobserver/                                     @open-telemetry/collector-contrib-approvers @dmitryax @rmfitzpatrick
 extension/observer/ecstaskobserver/                                 @open-telemetry/collector-contrib-approvers @rmfitzpatrick

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -101,6 +101,7 @@ body:
       - extension/jaegerremotesampling
       - extension/oauth2clientauth
       - extension/observer
+      - extension/observer/cfgardenobserver
       - extension/observer/dockerobserver
       - extension/observer/ecsobserver
       - extension/observer/ecstaskobserver

.github/ISSUE_TEMPLATE/feature_request.yaml

@@ -95,6 +95,7 @@ body:
       - extension/jaegerremotesampling
       - extension/oauth2clientauth
       - extension/observer
+      - extension/observer/cfgardenobserver
       - extension/observer/dockerobserver
       - extension/observer/ecsobserver
       - extension/observer/ecstaskobserver

.github/ISSUE_TEMPLATE/other.yaml

@@ -95,6 +95,7 @@ body:
       - extension/jaegerremotesampling
       - extension/oauth2clientauth
       - extension/observer
+      - extension/observer/cfgardenobserver
       - extension/observer/dockerobserver
       - extension/observer/ecsobserver
       - extension/observer/ecstaskobserver

.github/ISSUE_TEMPLATE/unmaintained.yaml

@@ -100,6 +100,7 @@ body:
       - extension/jaegerremotesampling
       - extension/oauth2clientauth
       - extension/observer
+      - extension/observer/cfgardenobserver
       - extension/observer/dockerobserver
       - extension/observer/ecsobserver
       - extension/observer/ecstaskobserver

cmd/githubgen/allowlist.txt

@@ -16,3 +16,7 @@ rlankfo
 swar8080
 zpzhuSplunk
 thmshmm
+cemdk
+tomasmota
+m1rp
+jriguera

cmd/otelcontribcol/builder-config.yaml

@@ -28,11 +28,12 @@ extensions:
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/httpforwarderextension v0.104.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/jaegerremotesampling v0.104.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/oauth2clientauthextension v0.104.0
+  - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/cfgardenobserver v0.104.0
+  - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/dockerobserver v0.104.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/ecsobserver v0.104.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/ecstaskobserver v0.104.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/hostobserver v0.104.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/k8sobserver v0.104.0
-  - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/dockerobserver v0.104.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/oidcauthextension v0.104.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/opampextension v0.104.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/pprofextension v0.104.0
@@ -485,4 +486,5 @@ replaces:
   - github.com/open-telemetry/opentelemetry-collector-contrib/internal/pdatautil => ../../internal/pdatautil
   - github.com/open-telemetry/opentelemetry-collector-contrib/exporter/otelarrowexporter => ../../exporter/otelarrowexporter
   - github.com/open-telemetry/opentelemetry-collector-contrib/receiver/otelarrowreceiver => ../../receiver/otelarrowreceiver
+  - github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/cfgardenobserver => ../../extension/observer/cfgardenobserver
   - github.com/open-telemetry/opentelemetry-collector-contrib/exporter/rabbitmqexporter => ../../exporter/rabbitmqexporter

cmd/otelcontribcol/go.mod

@@ -80,6 +80,7 @@ require (
 	github.com/open-telemetry/opentelemetry-collector-contrib/extension/httpforwarderextension v0.104.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/extension/jaegerremotesampling v0.104.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/extension/oauth2clientauthextension v0.104.0
+	github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/cfgardenobserver v0.104.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/dockerobserver v0.104.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/ecsobserver v0.104.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/ecstaskobserver v0.104.0
@@ -1327,4 +1328,6 @@ replace github.com/open-telemetry/opentelemetry-collector-contrib/exporter/otela
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/receiver/otelarrowreceiver => ../../receiver/otelarrowreceiver
 
+replace github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/cfgardenobserver => ../../extension/observer/cfgardenobserver
+
 replace github.com/open-telemetry/opentelemetry-collector-contrib/exporter/rabbitmqexporter => ../../exporter/rabbitmqexporter

extension/observer/cfgardenobserver/Makefile

@@ -0,0 +1 @@
+include ../../../Makefile.Common

extension/observer/cfgardenobserver/README.md

@@ -0,0 +1,53 @@
+# Cloud Foundry Garden Observer Extension
+
+<!-- status autogenerated section -->
+| Status        |           |
+| ------------- |-----------|
+| Stability     | [development]  |
+| Distributions | [] |
+| Issues        | [![Open issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aopen%20label%3Aextension%2Fcfgardenobserver%20&label=open&color=orange&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aopen+is%3Aissue+label%3Aextension%2Fcfgardenobserver) [![Closed issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aclosed%20label%3Aextension%2Fcfgardenobserver%20&label=closed&color=blue&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aclosed+is%3Aissue+label%3Aextension%2Fcfgardenobserver) |
+| [Code Owners](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md#becoming-a-code-owner)    | [@crobert-1](https://www.github.com/crobert-1), [@cemdk](https://www.github.com/cemdk), [@tomasmota](https://www.github.com/tomasmota), [@m1rp](https://www.github.com/m1rp), [@jriguera](https://www.github.com/jriguera) |
+
+[development]: https://github.com/open-telemetry/opentelemetry-collector#development
+<!-- end autogenerated section -->
+
+Cloud Foundry (CF) is a platform as a service (PaaS) which has implemented their own container technology. The component in charge of providing a local API in each node (also known as "diego-cell") is named Garden.
+
+The `cfgarden_observer` looks at the current host to discover Garden containers.
+
+## Example Config
+
+```yaml
+extensions:
+  cfgarden_observer:
+    # url of the Garden socket, defaults to unix:///var/vcap/data/garden/garden.sock 
+    endpoint: my/path/to/garden.sock
+    # determines how often to look for changes in endpoints.
+    refresh_interval: 30s
+
+receivers:
+  receiver_creator:
+    watch_observers: [cfgarden_observer]
+    receivers:
+      prometheus_simple:
+        rule: type == "container" && name == "myapp"
+        config:
+          metrics_path: /metrics
+          endpoint: '`endpoint`'
+```
+
+### Configuration
+
+| Name             | Type   | Default                                  | Docs                                                   |
+|------------------|--------|------------------------------------------|--------------------------------------------------------|
+| refresh_interval | string | 60s                                      | Determines how often to look for changes in endpoints. |
+| endpoint         | string | unix:///var/vcap/data/garden/garden.sock | The endpoint to connect to the Garden API.             |
+
+### Endpoint Variables
+
+Endpoint variables exposed by this observer are as follows.
+
+| Variable  | Description                                                                                |
+|-----------|--------------------------------------------------------------------------------------------|
+| type      | this value is always `container`                                                                              |
+| name      | name of the Garden container associated to the port                                        |

extension/observer/cfgardenobserver/config.go

@@ -0,0 +1,18 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package cfgardenobserver // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/cfgardenobserver"
+
+import (
+	"time"
+)
+
+// Config defines configuration for CF Garden observer.
+type Config struct {
+	// The URL of the CF Garden api. Default is "unix:///var/vcap/data/garden/garden.sock"
+	Endpoint string `mapstructure:"endpoint"`
+
+	// RefreshInterval determines the frequency at which the observer
+	// needs to poll for collecting information about new processes.
+	RefreshInterval time.Duration `mapstructure:"refresh_interval"`
+}

extension/observer/cfgardenobserver/config_test.go

@@ -0,0 +1,55 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package cfgardenobserver
+
+import (
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/confmap/confmaptest"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/cfgardenobserver/internal/metadata"
+)
+
+func TestLoadConfig(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		id       component.ID
+		expected component.Config
+	}{
+		{
+			id: component.NewID(metadata.Type),
+			expected: &Config{
+				Endpoint:        "unix:///var/vcap/data/garden/garden.sock",
+				RefreshInterval: 1 * time.Minute,
+			},
+		},
+		{
+			id: component.NewIDWithName(metadata.Type, "all_settings"),
+			expected: &Config{
+				Endpoint:        "unix:///var/vcap/data/garden/custom.sock",
+				RefreshInterval: 20 * time.Second,
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.id.String(), func(t *testing.T) {
+			cm, err := confmaptest.LoadConf(filepath.Join("testdata", "config.yaml"))
+			require.NoError(t, err)
+			factory := NewFactory()
+			cfg := factory.CreateDefaultConfig()
+			sub, err := cm.Sub(tt.id.String())
+			require.NoError(t, err)
+			require.NoError(t, sub.Unmarshal(cfg))
+
+			assert.NoError(t, component.ValidateConfig(cfg))
+			assert.Equal(t, tt.expected, cfg)
+		})
+	}
+}

extension/observer/cfgardenobserver/doc.go

@@ -0,0 +1,6 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+//go:generate mdatagen metadata.yaml
+
+package cfgardenobserver // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/cfgardenobserver"

extension/observer/cfgardenobserver/extension.go

@@ -0,0 +1,36 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package cfgardenobserver // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/cfgardenobserver"
+
+import (
+	"time"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/extension"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer"
+)
+
+type cfGardenObserver struct {
+	*observer.EndpointsWatcher
+
+	component.StartFunc
+	component.ShutdownFunc
+}
+
+var _ extension.Extension = (*cfGardenObserver)(nil)
+
+func newObserver(params extension.Settings, _ *Config) (extension.Extension, error) {
+	g := &cfGardenObserver{}
+	g.EndpointsWatcher = observer.NewEndpointsWatcher(g, time.Second, params.Logger)
+
+	return g, nil
+}
+
+func (g *cfGardenObserver) ListEndpoints() []observer.Endpoint {
+	// TODO: Implement the logic to list the endpoints.
+	endpoints := make([]observer.Endpoint, 0)
+
+	return endpoints
+}

extension/observer/cfgardenobserver/extension_test.go

@@ -0,0 +1,35 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package cfgardenobserver
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component/componenttest"
+	"go.opentelemetry.io/collector/extension/extensiontest"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer"
+)
+
+func TestStartAndStopObserver(t *testing.T) {
+	factory := NewFactory()
+	params := extensiontest.NewNopSettings()
+	ext, err := newObserver(params, factory.CreateDefaultConfig().(*Config))
+	require.NoError(t, err)
+	require.NotNil(t, ext)
+
+	obvs, ok := ext.(*cfGardenObserver)
+	require.True(t, ok)
+
+	ctx := context.Background()
+	require.NoError(t, obvs.Start(ctx, componenttest.NewNopHost()))
+
+	expected := obvs.ListEndpoints()
+	want := []observer.Endpoint{}
+	require.Equal(t, want, expected)
+
+	require.NoError(t, obvs.Shutdown(ctx))
+}

extension/observer/cfgardenobserver/factory.go

@@ -0,0 +1,44 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package cfgardenobserver // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/cfgardenobserver"
+
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/extension"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer/cfgardenobserver/internal/metadata"
+)
+
+const (
+	defaultCollectionInterval = 1 * time.Minute
+	defaultEndpoint           = "unix:///var/vcap/data/garden/garden.sock"
+)
+
+// NewFactory creates a factory for HostObserver extension.
+func NewFactory() extension.Factory {
+	return extension.NewFactory(
+		metadata.Type,
+		createDefaultConfig,
+		createExtension,
+		metadata.ExtensionStability,
+	)
+}
+
+func createDefaultConfig() component.Config {
+	return &Config{
+		RefreshInterval: defaultCollectionInterval,
+		Endpoint:        defaultEndpoint,
+	}
+}
+
+func createExtension(
+	_ context.Context,
+	params extension.Settings,
+	cfg component.Config,
+) (extension.Extension, error) {
+	return newObserver(params, cfg.(*Config))
+}