[receiver/receiver_creator] Add support for enabling receivers/scrapers from K8s hints

[ChrsMark]

Description

This PR implements the metrics' part suggested at #34427 (comment). The current implementation only supports hints coming from Pods (wip with Logs included-> https://github.com/open-telemetry/opentelemetry-collector-contrib/compare/main...ChrsMark:opentelemetry-collector-contrib:logs_hints?expand=1)

This PR implements what it was decided at #34427 (comment).

See the README docs for the description of this feature: https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/35617/files#diff-4127365c4062a7510fb7fede0fa239e9232549732898303d94c12fef0433d39d

TODOs:

• turn-on/off the feature using a setting
• add docs
• add tests

Link to tracking issue

Part of #34427

Testing

Added unit-tests.

Documentation

Added

How to test this locally

1. Using the follow values to install the Collector's Helm chart:

mode: daemonset

image:
  repository: otelcontribcol-dev
  tag: "latest"
  pullPolicy: IfNotPresent

command:
  name: otelcontribcol

clusterRole:
  create: true
  rules:
   - apiGroups:
     - ''
     resources:
     - 'pods'
     - 'nodes'
     verbs:
     - 'get'
     - 'list'
     - 'watch'
   - apiGroups: [ "" ]
     resources: [ "nodes/proxy"]
     verbs: [ "get" ]
   - apiGroups:
       - ""
     resources:
       - nodes/stats
     verbs:
       - get
   - nonResourceURLs:
       - "/metrics"
     verbs:
       - get

config:
  extensions:
    k8s_observer:
      auth_type: serviceAccount
      node: ${env:K8S_NODE_NAME}
      observe_nodes: true
  exporters:
    debug:
      verbosity: basic
  receivers:
    receiver_creator/metrics:
      watch_observers: [ k8s_observer ]
      discovery:
        enabled: true
      receivers:

  service:
    extensions: [health_check, k8s_observer]
    telemetry:
      logs:
        level: DEBUG
    pipelines:
      metrics:
        receivers: [ receiver_creator/metrics ]
        processors: [ batch ]
        exporters: [ debug ]

2. Use the following target Pod which consists of 2 containers:

apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-conf
data:
  nginx.conf: |
    user  nginx;
    worker_processes  1;
    error_log  /dev/stderr warn;
    pid        /var/run/nginx.pid;
    events {
      worker_connections  1024;
    }
    http {
      include       /etc/nginx/mime.types;
      default_type  application/octet-stream;
    
      log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                        '$status $body_bytes_sent "$http_referer" '
                        '"$http_user_agent" "$http_x_forwarded_for"';
      access_log  /dev/stdout main;
      server {
          listen 80;
          server_name localhost;
    
          location /nginx_status {
              stub_status on;
          }
      }
      include /etc/nginx/conf.d/*;
    }
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: redis-deployment
  labels:
    app: redis
spec:
  replicas: 1
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
      annotations:
        # redis container port hints
        io.opentelemetry.discovery.metrics.6379/enabled: "true"
        io.opentelemetry.discovery.metrics.6379/scraper: redis
        io.opentelemetry.discovery.metrics.6379/config: |
          collection_interval: "20s"
          timeout: "10s"

        # nginx container port hints
        io.opentelemetry.discovery.metrics.80/enabled: "true"
        io.opentelemetry.discovery.metrics.80/scraper: nginx
        io.opentelemetry.discovery.metrics.80/config: |
          endpoint: "http://`endpoint`/nginx_status"
          collection_interval: "30s"
          timeout: "20s"
    spec:
      volumes:
      - name: nginx-conf
        configMap:
          name: nginx-conf
          items:
            - key: nginx.conf
              path: nginx.conf
      containers:
        - name: webserver
          image: nginx:latest
          ports:
            - containerPort: 80
              name: webserver
          volumeMounts:
            - mountPath: /etc/nginx/nginx.conf
              readOnly: true
              subPath: nginx.conf
              name: nginx-conf
        - image: redis
          imagePullPolicy: IfNotPresent
          name: redis
          ports:
            - name: redis
              containerPort: 6379
              protocol: TCP

3. After the target pod is deployed check the Collector logs and verify that 2 receivers are started properly and metrics are collected from both target containers:

2024-10-04T13:53:02.550Z	info	[email protected]/observerhandler.go:115	starting receiver	{"kind": "receiver", "name": "receiver_creator/metrics", "data_type": "metrics", "name": "nginx/e6d880c9-13a0-45e7-a3a1-27fa021802b4_80", "endpoint": "10.244.0.52:80", "endpoint_id": "k8s_observer/e6d880c9-13a0-45e7-a3a1-27fa021802b4/webserver(80)", "config": {"collection_interval":"20s","endpoint":"http://`endpoint`/nginx_status"}}
....
2024-10-04T13:53:02.550Z	info	[email protected]/observerhandler.go:115	starting receiver	{"kind": "receiver", "name": "receiver_creator/metrics", "data_type": "metrics", "name": "redis/e6d880c9-13a0-45e7-a3a1-27fa021802b4_6379", "endpoint": "10.244.0.52:6379", "endpoint_id": "k8s_observer/e6d880c9-13a0-45e7-a3a1-27fa021802b4/redis(6379)", "config": {"collection_interval":"20s","endpoint":"10.244.0.52:6379"}}
2024-10-04T13:53:03.646Z	info	MetricsExporter	{"kind": "exporter", "data_type": "metrics", "name": "debug", "resource metrics": 2, "metrics": 30, "data points": 38}
2024-10-04T13:53:06.547Z	debug	memorylimiter/memorylimiter.go:181	Currently used memory.	{"kind": "processor", "name": "memory_limiter", "pipeline": "traces", "cur_mem_mib": 39}
2024-10-04T13:53:11.547Z	debug	memorylimiter/memorylimiter.go:181	Currently used memory.	{"kind": "processor", "name": "memory_limiter", "pipeline": "traces", "cur_mem_mib": 39}
2024-10-04T13:53:16.546Z	debug	memorylimiter/memorylimiter.go:181	Currently used memory.	{"kind": "processor", "name": "memory_limiter", "pipeline": "traces", "cur_mem_mib": 40}

More testing target Pods
busybox-multi-logs.txt
busybox-single-logs.txt
redis-nginx-mutli.txt
redis-single.txt
redis-single-logs.txt

[ChrsMark]

@dmitryax I have opened this for review, please feel free to take a look when you get the chance.

Since #35544 was merged I could also add the Logs' part here if that's easier for you to review, however that would make the PR significantly bigger. Let me know what you prefer.

Update Logs included-> https://github.com/open-telemetry/opentelemetry-collector-contrib/compare/main...ChrsMark:opentelemetry-collector-contrib:logs_hints?expand=1

[ChrsMark]

Thank's @dmitryax, I've removed the redundant config field. It should be good to go now.

[ChrsMark]

Thank's @dmitryax . Comments should be addressed now. PTAL.