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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

General notes

  • The autoconfigure module registers Java shutdown hooks to shut down the SDK when appropriate. Please note that since this project uses java.util.logging for all of it's logging, some of that logging may be suppressed during shutdown hooks. This is a bug in the JDK itself, and not something we can control. If you require logging during shutdown hooks, please consider using System.out rather than a logging framework that might shut itself down in a shutdown hook, thus suppressing your log messages. See this JDK bug for more details.

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 traces and metrics 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.traces.endpoint OTEL_EXPORTER_OTLP_TRACES_ENDPOINT The OTLP traces 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.metrics.endpoint OTEL_EXPORTER_OTLP_METRICS_ENDPOINT The OTLP metrics 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 commas 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 http://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

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.