# Opentelemetry::Common

The `opentelemetry-common` gem provides common helpers for OpenTelemetry.

## What is OpenTelemetry?

OpenTelemetry is an open source observability framework, providing a general-purpose API, SDK, and related tools required for the instrumentation of cloud-native software, frameworks, and libraries.

OpenTelemetry provides a single set of APIs, libraries, agents, and collector services to capture distributed traces and metrics from your application. You can analyze them using Prometheus, Jaeger, and other observability tools.

## How does this gem fit in?

The `opentelemetry-common` gem provides common helpers for semantic conventions, context propagation patterns, etc. It depends only on the OpenTelemetry Ruby API, not the SDK.

## How do I get started?

Install the gem using:

```
gem install opentelemetry-common
```

Or, if you use Bundler, include `opentelemetry-common` in your `Gemfile`.

```rb
require 'opentelemetry/common'

# TODO: example of semantic convention helpers

# Context propagation in Net::HTTP client
OpenTelemetry::Common::HTTP::ClientContext.with_attributes('peer.service' => 'example') do
  Net::HTTP.get('example.com', '/index.html')
end

# Context propagation in Net::HTTP instrumentation
attributes = OpenTelemetry::Common::HTTP::ClientContext.attributes
tracer.in_span(
  HTTP_METHODS_TO_SPAN_NAMES[req.method],
  attributes: attributes.merge(
    'http.method' => req.method,
    'http.scheme' => USE_SSL_TO_SCHEME[use_ssl?],
    'http.target' => req.path,
    'peer.hostname' => @address,
    'peer.port' => @port
  ),
  kind: :client
) do |span|
  ...
end
```

## How can I get involved?

The `opentelemetry-common` gem source is on github, along with related gems.

The OpenTelemetry Ruby gems are maintained by the OpenTelemetry-Ruby special interest group (SIG). You can get involved by joining us on our gitter channel or attending our weekly meeting. See the meeting calendar for dates and times. For more information on this and other language SIGs, see the OpenTelemetry community page.

## License

The `opentelemetry-common` gem is distributed under the Apache 2.0 license. See LICENSE for more information.