opentelemetry-java/sdk-extensions/autoconfigure

OpenTelemetry SDK Autoconfigure

This artifact implements environment-based autoconfiguration of the OpenTelemetry SDK. This can be an alternative to programmatic configuration using the normal SDK builders.

All options support being passed as Java system properties, e.g., -Dotel.traces.exporter=zipkin or environment variables, e.g., OTEL_TRACES_EXPORTER=zipkin.

Contents

• Exporters
  • OTLP exporter (both span and metric exporters)
  • Jaeger exporter
  • Zipkin exporter
  • Prometheus exporter
  • Logging exporter
• Trace context propagation
• OpenTelemetry Resource
• Batch span processor
• Sampler
• Span limits
• Interval metric reader
• Customizing the OpenTelemetry SDK

Exporters

The following configuration properties are common to all exporters:

System property	Environment variable	Purpose
otel.traces.exporter	OTEL_TRACES_EXPORTER	The exporter to be used for tracing. Default is otlp. none means no autoconfigured exporter.
otel.metrics.exporter	OTEL_METRICS_EXPORTER	The exporter to be used for metrics. Default is otlp. none means no autoconfigured exporter.

OTLP exporter (both span and metric exporters)

The OpenTelemetry Protocol (OTLP) span and metric exporters

System property	Environment variable	Description
otel.traces.exporter=otlp (default)	OTEL_TRACES_EXPORTER=otlp	Select the OpenTelemetry exporter for tracing (default)
otel.metrics.exporter=otlp (default)	OTEL_METRICS_EXPORTER=otlp	Select the OpenTelemetry exporter for metrics (default)
otel.exporter.otlp.endpoint	OTEL_EXPORTER_OTLP_ENDPOINT	The OTLP endpoint to connect to. Must be a URL with a scheme of either http or https based on the use of TLS. Default is http://localhost:4317.
otel.exporter.otlp.headers	OTEL_EXPORTER_OTLP_HEADERS	Key-value pairs separated by semicolons to pass as request headers
otel.exporter.otlp.timeout	OTEL_EXPORTER_OTLP_TIMEOUT	The maximum waiting time allowed to send each batch. Default is 1000.

To configure the service name for the OTLP exporter, add the service.name key to the OpenTelemetry Resource (see below), e.g. OTEL_RESOURCE_ATTRIBUTES=service.name=myservice.

Jaeger exporter

The Jaeger exporter. This exporter uses gRPC for its communications protocol.

System property	Environment variable	Description
otel.traces.exporter=jaeger	OTEL_TRACES_EXPORTER=jaeger	Select the Jaeger exporter
otel.exporter.jaeger.endpoint	OTEL_EXPORTER_JAEGER_ENDPOINT	The Jaeger gRPC endpoint to connect to. Default is localhost:14250.

Zipkin exporter

The Zipkin exporter. It sends JSON in Zipkin format to a specified HTTP URL.

System property	Environment variable	Description
otel.traces.exporter=zipkin	OTEL_TRACES_EXPORTER=zipkin	Select the Zipkin exporter
otel.exporter.zipkin.endpoint	OTEL_EXPORTER_ZIPKIN_ENDPOINT	The Zipkin endpoint to connect to. Default is http://localhost:9411/api/v2/spans. Currently only HTTP is supported.

Prometheus exporter

The Prometheus exporter.

System property	Environment variable	Description
otel.metrics.exporter=prometheus	OTEL_METRICS_EXPORTER=prometheus	Select the Prometheus exporter
otel.exporter.prometheus.port	OTEL_EXPORTER_PROMETHEUS_PORT	The local port used to bind the prometheus metric server. Default is 9464.
otel.exporter.prometheus.host	OTEL_EXPORTER_PROMETHEUS_HOST	The local address used to bind the prometheus metric server. Default is 0.0.0.0.

Note that this is a pull exporter - it opens up a server on the local process listening on the specified host and port, which a Prometheus server scrapes from.

Logging exporter

The logging exporter prints the name of the span along with its attributes to stdout. It's mainly used for testing and debugging.

System property	Environment variable	Description
otel.traces.exporter=logging	OTEL_TRACES_EXPORTER=logging	Select the logging exporter for tracing
otel.metrics.exporter=logging	OTEL_METRICS_EXPORTER=logging	Select the logging exporter for metrics
otel.exporter.logging.prefix	OTEL_EXPORTER_LOGGING_PREFIX	An optional string printed in front of the span name and attributes.

Propagator

The propagators determine which distributed tracing header formats are used, and which baggage propagation header formats are used.

System property	Environment variable	Description
otel.propagators	OTEL_PROPAGATORS	The propagators to be used. Use a comma-separated list for multiple propagators. Default is tracecontext,baggage (W3C).

Supported values are

• "tracecontext": W3C Trace Context (add baggage as well to include W3C baggage)
• "baggage": W3C Baggage
• "b3": B3 Single
• "b3multi": B3 Multi
• "jaeger": Jaeger (includes Jaeger baggage)
• "xray": AWS X-Ray
• "ottrace": OT Trace

OpenTelemetry Resource

The OpenTelemetry Resource is a representation of the entity producing telemetry.

System property	Environment variable	Description
otel.resource.attributes	OTEL_RESOURCE_ATTRIBUTES	Specify resource attributes in the following format: key1=val1,key2=val2,key3=val3

You almost always want to specify the service.name for your application. It corresponds to how you describe the application, for example authservice could be an application that authenticates requests, and cats could be an application that returns information about cats. This means you would specify resource attributes something like OTEL_RESOURCE_ATTRIBUTES=service.name=authservice, or -Dotel.resource.attributes=service.name=cats,service.namespace=mammals.

Batch span processor

System property	Environment variable	Description
otel.bsp.schedule.delay	OTEL_BSP_SCHEDULE_DELAY	The interval, in milliseconds, between two consecutive exports. Default is 5000.
otel.bsp.max.queue.size	OTEL_BSP_MAX_QUEUE_SIZE	The maximum queue size. Default is 2048.
otel.bsp.max.export.batch.size	OTEL_BSP_MAX_EXPORT_BATCH_SIZE	The maximum batch size. Default is 512.
otel.bsp.export.timeout	OTEL_BSP_EXPORT_TIMEOUT	The maximum allowed time, in milliseconds, to export data. Default is 30000.

Sampler

The sampler configures whether spans will be recorded for any call to SpanBuilder.startSpan.

System property	Environment variable	Description
otel.traces.sampler	OTEL_TRACES_SAMPLER	The sampler to use for tracing. Defaults to parentbased_always_on
otel.traces.sampler.arg	OTEL_TRACES_SAMPLER_ARG	An argument to the configured tracer if supported, for example a ratio.

Supported values for otel.traces.sampler are

• "always_on": AlwaysOnSampler
• "always_off": AlwaysOffSampler
• "traceidratio": TraceIdRatioBased. otel.traces.sampler.arg sets the ratio.
• "parentbased_always_on": ParentBased(root=AlwaysOnSampler)
• "parentbased_always_off": ParentBased(root=AlwaysOffSampler)
• "parentbased_traceidratio": ParentBased(root=TraceIdRatioBased). otel.traces.sampler.arg sets the ratio.

Span limits

These properties can be used to control the maximum size of recordings per span.

System property	Environment variable	Description
otel.span.attribute.count.limit	OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT	The maximum number of attributes per span. Default is 128.
otel.span.event.count.limit	OTEL_SPAN_EVENT_COUNT_LIMIT	The maximum number of events per span. Default is 128.
otel.span.link.count.limit	OTEL_SPAN_LINK_COUNT_LIMIT	The maximum number of links per span. Default is 128

Interval metric reader

System property	Environment variable	Description
otel.imr.export.interval	OTEL_IMR_EXPORT_INTERVAL	The interval, in milliseconds, between pushes to the exporter. Default is 60000.

Customizing the OpenTelemetry SDK

Autoconfiguration exposes SPI hooks for customizing behavior programmatically as needed. It's recommended to use the above configuration properties where possible, only implementing the SPI to add functionality not found in the SDK by default.