Building a custom collector

If you are planning to build and debug custom collector receivers, processors, extensions, or exporters, you are going to need your own Collector instance. That will allow you to launch and debug your OpenTelemetry Collector components directly within your favorite Golang IDE.

The other interesting aspect of approaching the component development this way is that you can use all the debugging features from your IDE (stack traces are great teachers!) to understand how the Collector itself interacts with your component code.

The OpenTelemetry Community developed a tool called OpenTelemetry Collector builder (or ocb for short) to assist people in assembling their own distribution, making it easy to build a distribution that includes their custom components along with components that are publicly available.

As part of the process the builder will generate the Collector’s source code, which you can use to help build and debug your own custom components, so let’s get started.

Step 1 - Install the builder

The ocb binary is available as a downloadable asset from OpenTelemetry Collector releases. You will find the list of assets at the bottom of the page. Assets are named based on OS and chipset, so download the one that fits your configuration.

The binary has a pretty long name, so you can simply rename it to ocb; and if you are running Linux or macOS, you will also need to provide execution permissions for the binary.

Open your terminal and type the following commands to accomplish both operations:

mv ocb_0.94.0_darwin_amd64 ocb
chmod 777 ocb

To make sure the ocb is ready to be used, go to your terminal and type ./ocb help, and once you hit enter you should have the output of the help command showing up in your console.

Step 2 - Create a builder manifest file

The builder’s manifest file is a yaml where you pass information about the code generation and compile process combined with the components that you would like to add to your Collector’s distribution.

The manifest starts with a map named dist which contains tags to help you configure the code generation and compile process. In fact, all the tags for dist are the equivalent of the ocb command line flags.

Here are the tags for the dist map:

TagDescriptionOptionalDefault Value
module:The module name for the new distribution, following Go mod conventions. Optional, but recommended.Yesgo.opentelemetry.io/collector/cmd/builder
name:The binary name for your distributionYesotelcol-custom
description:A long name for the application.YesCustom OpenTelemetry Collector distribution
otelcol_version:The OpenTelemetry Collector version to use as base for the distribution.Yes0.94.0
output_path:The path to write the output (sources and binary).Yes/var/folders/86/s7l1czb16g124tng0d7wyrtw0000gn/T/otelcol-distribution3618633831
version:The version for your custom OpenTelemetry Collector.Yes1.0.0
go:Which Go binary to use to compile the generated sources.Yesgo from the PATH

As you can see on the table above, all the dist tags are optional, so you will be adding custom values for them depending if your intentions to make your custom Collector distribution available for consumption by other users or if you are simply leveraging the ocb to bootstrap your component development and testing environment.

For this tutorial, you will be creating a Collector’s distribution to support the development and testing of components.

Go ahead and create a manifest file named builder-config.yaml with the following content:

builder-config.yaml

dist:
  name: otelcol-dev
  description: Basic OTel Collector distribution for Developers
  output_path: ./otelcol-dev

Now you need to add the modules representing the components you want to be incorporated in this custom Collector distribution. Take a look at the ocb configuration documentation to understand the different modules and how to add the components.

We will be adding the following components to our development and testing collector distribution:

  • Exporters: OTLP and Debug1
  • Receivers: OTLP
  • Processors: Batch

The builder-config.yaml manifest file will look like this after adding the components:

builder-config.yaml

dist:
  name: otelcol-dev
  description: Basic OTel Collector distribution for Developers
  output_path: ./otelcol-dev
  otelcol_version: 0.94.0

exporters:
  - gomod:
      # NOTE: Prior to v0.86.0 use the `loggingexporter` instead of `debugexporter`.
      go.opentelemetry.io/collector/exporter/debugexporter v0.94.0
  - gomod:
      go.opentelemetry.io/collector/exporter/otlpexporter v0.94.0

processors:
  - gomod:
      go.opentelemetry.io/collector/processor/batchprocessor v0.94.0

receivers:
  - gomod:
      go.opentelemetry.io/collector/receiver/otlpreceiver v0.94.0

Step 3 - Generating the Code and Building your Collector’s distribution

All you need now is to let the ocb do it’s job, so go to your terminal and type the following command:

./ocb --config builder-config.yaml

If everything went well, here is what the output of the command should look like:

2022-06-13T14:25:03.037-0500	INFO	internal/command.go:85	OpenTelemetry Collector distribution builder	{"version": "0.94.0", "date": "2023-01-03T15:05:37Z"}
2022-06-13T14:25:03.039-0500	INFO	internal/command.go:108	Using config file	{"path": "builder-config.yaml"}
2022-06-13T14:25:03.040-0500	INFO	builder/config.go:99	Using go	{"go-executable": "/usr/local/go/bin/go"}
2022-06-13T14:25:03.041-0500	INFO	builder/main.go:76	Sources created	{"path": "./otelcol-dev"}
2022-06-13T14:25:03.445-0500	INFO	builder/main.go:108	Getting go modules
2022-06-13T14:25:04.675-0500	INFO	builder/main.go:87	Compiling
2022-06-13T14:25:17.259-0500	INFO	builder/main.go:94	Compiled	{"binary": "./otelcol-dev/otelcol-dev"}

As defined in the dist section of your config file, you now have a folder named otelcol-dev containing all the source code and the binary for your Collector’s distribution.

The folder structure should look like this:

.
├── builder-config.yaml
├── ocb
└── otelcol-dev
    ├── components.go
    ├── components_test.go
    ├── go.mod
    ├── go.sum
    ├── main.go
    ├── main_others.go
    ├── main_windows.go
    └── otelcol-dev

You can now use the generated code to bootstrap your component development projects and easily build and distribute your own collector distribution with your components.

Further reading:


  1. Prior to v0.86.0 use the loggingexporter instead of debugexporter↩︎