Mastering OpenTelemetry Collector: A Comprehensive Guide to Metrics, Logs, and Data Processing

Nicolas Fränkel

Introduction

In the evolving world of observability and cloud infrastructure, the OpenTelemetry Collector has emerged as a vital tool. As a central component in the OpenTelemetry ecosystem, the Collector plays a crucial role in managing data from various sources. This guide explores the OpenTelemetry Collector, its functionalities, and how to effectively utilize it for metrics, logs, and data processing.

Understanding the OpenTelemetry Collector

The OpenTelemetry Collector is designed to receive, process, and export telemetry data, including logs, metrics, and traces. While it is a fundamental element in the OpenTelemetry architecture, it operates independently of the W3C Trace Context. This flexibility allows it to be used in various scenarios, including integrating with monitoring solutions like Prometheus and visualization tools like Grafana.

Key Features of the OpenTelemetry Collector

Data Types: The Collector handles three primary data types:
- Logs: System and application logs.
- Metrics: Performance data and usage statistics.
- Traces: Distributed traces that track requests through a system.
Push and Pull Models: It supports both push and pull models for data collection:
- Push Model: Data is sent from the source to the Collector.
- Pull Model: The Collector fetches data from the source.
Operations: The Collector performs several operations, including:
- Reads: Collecting data from various sources.
- Transforms: Modifying data to fit desired formats or standards.
- Writes: Exporting processed data to various destinations.

Getting Started with OpenTelemetry Collector

Setting Up Your Environment

To begin, you’ll need to set up an environment with Docker Compose to run the OpenTelemetry Collector. Here’s a simple configuration for scraping metrics from a Prometheus-compatible endpoint:

yaml
version: "3"
services:
  fake-metrics:
    build: ./fake-metrics-generator
  collector:
    image: otel/opentelemetry-collector:0.87.0
    environment:
      - METRICS_HOST=fake-metrics
      - METRICS_PORT=5000
    volumes:
      - ./config/collector/config.yml:/etc/otelcol/config.yaml:ro

Configuring the Collector
Create a configuration file (config.yml) to define how the Collector handles data.

Basic Configuration
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receivers:
  prometheus:
    config:
      scrape_configs:
        - job_name: fake-metrics
          scrape_interval: 3s
          static_configs:
            - targets: [ "${env.METRICS_HOST}:${env.METRICS_PORT}" ]
exporters:
  logging:
    loglevel: debug
service:
  pipelines:
    metrics:
      receivers: [ "prometheus" ]
      exporters: [ "logging" ]

Advanced Configuration
Exposing Metrics to Prometheus

To expose metrics to Prometheus and visualize them in Grafana, update your configuration:

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exporters:
  prometheus:
    endpoint: ":${env:PROMETHEUS_PORT}"
  logging:
    loglevel: debug
service:
  pipelines:
    metrics:
      receivers: [ "prometheus" ]
      exporters: [ "prometheus", "logging" ]

Data Processing with Processors

The Collector can transform data to meet specific requirements. For instance, to add labels or rename metrics:

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processors:
  metricstransform:
    transforms:
      - include: ^fake_(.*)$
        match_type: regexp
        action: update
        operations:
          - action: add_label
            new_label: origin
            new_value: fake
          - action: update
            new_name: $${1}
service:
  pipelines:
    metrics:
      receivers: [ "prometheus" ]
      processors: [ "metricstransform" ]
      exporters: [ "prometheus" ]

Connecting Receivers and Exporters

You can also use connectors to link receivers and exporters, such as connecting a log receiver to a metrics exporter:

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receivers:
  filelog:
    include: [ "/var/logs/generated.log" ]

connectors:
  count:
    requests.errors:
      description: Number of 500 errors
      condition: [ "status == 500 " ]
service:
  pipelines:
    logs:
      receivers: [ "filelog" ]
      exporters: [ "count" ]
    metrics:
      receivers: [ "prometheus", "count" ]

Manipulating Logs

To manipulate log data, such as changing timestamps or removing fields, use log processors:

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receivers:
  filelog:
    include: [ "/var/logs/generated.log" ]
    operators:
      - type: json_parser
        timestamp:
          parse_from: attributes.datetime
          layout: "%d/%b/%Y:%H:%M:%S %z"
        severity:
          parse_from: attributes.status
          mapping:
            error: 5xx
            warn: 4xx
            info: 3xx
            debug: 2xx
      - id: remove_body
        type: remove
        field: body
      - id: remove_datetime
        type: remove
        field: attributes.datetime
      - id: remove_status
        type: remove
        field: attributes.status
exporters:
  loki:
    endpoint: "http://loki:3100/loki/api/v1/push"
service:
  pipelines:
    logs:
      receivers: [ "filelog" ]
      exporters: [ "loki" ]

Conclusion
The OpenTelemetry Collector is a powerful tool for managing telemetry data across different systems. Whether you are collecting metrics, logs, or traces, the Collector’s flexibility and configurability make it an essential component in any observability strategy. For further exploration, refer to the OpenTelemetry Collector documentation.

For the complete source code and additional resources, visit our GitHub repository.