Configuration

Sources, highest priority first:

Application env

import Config

config :otel,
  trace: [
    resource: Otel.SDK.Resource.create(%{"service.name" => "my_app"}),
    sampler: :parentbased_always_on,
    exporter: :otlp,
    processor: :batch,
    span_limits: %{attribute_count_limit: 256}
  ],
  metrics: [
    resource: Otel.SDK.Resource.create(%{"service.name" => "my_app"}),
    exporter: :otlp,
    reader_config: %{export_interval_ms: 30_000}
  ],
  logs: [
    resource: Otel.SDK.Resource.create(%{"service.name" => "my_app"}),
    exporter: :otlp,
    processor: :batch
  ],
  propagators: [:tracecontext, :baggage]

OS environment

export OTEL_SERVICE_NAME=my_app
export OTEL_RESOURCE_ATTRIBUTES="deployment.environment=prod,service.version=1.2.3"
export OTEL_TRACES_SAMPLER=parentbased_always_on
export OTEL_TRACES_EXPORTER=otlp
export OTEL_METRICS_EXPORTER=otlp
export OTEL_METRIC_EXPORT_INTERVAL=30000
export OTEL_LOGS_EXPORTER=otlp
export OTEL_PROPAGATORS=tracecontext,baggage

Declarative YAML (OTEL_CONFIG_FILE)

Schema: OpenTelemetry Configuration v1.0.0.

# /etc/otel/config.yaml
file_format: "1.0"

resource:
  attributes_list: ${OTEL_RESOURCE_ATTRIBUTES}

propagator:
  composite:
    - tracecontext:
    - baggage:

tracer_provider:
  sampler:
    parent_based:
      root:
        always_on:
  processors:
    - batch:
        exporter:
          otlp_http:
            endpoint: ${OTEL_EXPORTER_OTLP_ENDPOINT:-http://localhost:4318}/v1/traces

meter_provider:
  readers:
    - periodic:
        exporter:
          otlp_http:
            endpoint: ${OTEL_EXPORTER_OTLP_ENDPOINT:-http://localhost:4318}/v1/metrics

logger_provider:
  processors:
    - batch:
        exporter:
          otlp_http:
            endpoint: ${OTEL_EXPORTER_OTLP_ENDPOINT:-http://localhost:4318}/v1/logs

export OTEL_CONFIG_FILE=/etc/otel/config.yaml

${VAR} / ${VAR:-default} substitution works anywhere. More examples in test/fixtures/v1.0.0/.

Disable the SDK

OTEL_SDK_DISABLED=true makes telemetry calls no-ops. Propagator stays active.

Selectors

Module-valued options (exporter:, processor:, sampler:, items in propagators:) accept:

• a shortcut atom (see tables below)
• a module — same as {Module, %{}}
• a {module, %{...}} tuple

Trace pillar

Metrics pillar

Logs pillar

Propagators

Deduplicated. [:none] or [] → Noop. :b3 / :b3multi / :jaeger / :xray / :ottrace raise; supply a custom module instead.

OTLP HTTP — SSL / TLS

The OTLP HTTP exporter uses Erlang's :httpc. For https:// endpoints, certificate verification is enabled by default using system CA certificates (:public_key.cacerts_get/0).

To override the defaults — custom CA bundle, mutual TLS, etc. — pass the exporter explicitly with an ssl_options: keyword list:

config :otel,
  trace: [
    exporter:
      {Otel.OTLP.Trace.SpanExporter.HTTP,
       %{
         endpoint: "https://collector.example.com:4318/v1/traces",
         ssl_options: [
           verify: :verify_peer,
           cacertfile: "/etc/ssl/certs/ca.crt"
         ]
       }}
  ]

ssl_options: accepts any Erlang :ssl client_option. Common patterns:

The same {Module, opts} shape works for metrics: (Otel.OTLP.Metrics.MetricExporter.HTTP) and logs: (Otel.OTLP.Logs.LogRecordExporter.HTTP).