[Exporter] Add OTLP File Exporter for Traces

[ashish159357]

Problem :
Many existing systems use technologies like ZeroMQ (ZMQ), Kafka, RabbitMQ, etc., for data communication. However, to export traces from the OpenTelemetry Java Agent to such systems, developers must implement HTTP/gRPC support in their infrastructure, either to receive traces directly from the agent or via the OpenTelemetry Collector.

This requirement adds unnecessary complexity for developers who prefer using their own transport mechanisms.

Solution :
The OpenTelemetry Java Agent supported an exporter that writes traces to a file in OTLP format, developers would gain greater flexibility. They could then build a custom utility to read traces from the file and forward them using their preferred tech stack—without modifying their backend to support HTTP/gRPC.

This exporter enables them to:

• Write traces to a file in OTLP format.

• Build a custom utility to read traces from the file and forward them to their backend using their preferred tech stack.

• Fully customize their utility and backend while leveraging OpenTelemetry's protobuf library for trace processing.

[jack-berg]

Check out OtlpStdout{Signal}Exporters. They export spans / metrics / logs to a configurable OutputStream (defaults to stdout, but could be a rotating file output stream if you're willing to write some custom code). These are the java implementation of the OTLP file exporter from the spec.

The contents are meant to be read by collector's OTLP JSON file reciever.

This blog post details a concrete example of this.

[ashish159357]

for writing traces in protobuf format I have to write code.

[jack-berg]

You may be interested in https://github.com/open-telemetry/opentelemetry-java-contrib/tree/main/disk-buffering