Is OTLP file exporter required for SDKs?

[jack-berg]

The OTLP File exporter seems like it could be an implementation requirement for SDKs, but on closer inspection:

• It does not appear as a known value for OTEL_TRACES_EXPORTER, OTEL_METRICS_EXPORTER, OTEL_LOGS_EXPORTER
• It only appears in the spec compliance matrix under logs. Its not implemented by any SDKs so this may have been a mistake.

On one hand, it would be nice to be able to configure SDKs to export to files. On the other hand, supporting file export requires a variety of additional un-specified configuration options including the the name of the file, whether a file rotation strategy is used, and more. Additionally, supporting this in the SDK when the functionality exists in the collector duplicates effort.

[austinlparker]

It would be good if we could get more specific feedback about the intended usage, use cases, and related work on this.

[zeitlinger]

The intended usage is to be to counterpart of the otlpjsonfilereceiver component - which is currently under development:

open-telemetry/opentelemetry-collector-contrib#33846

[zeitlinger]

Regarding the spec, I'd propose

OTEL_LOGS_EXPORTER=stdout

and

OTEL_LOGS_EXPORTER=file
OTEL_LOGS_EXPORTER_FILE=/path/to/file

wdyt?

[austinlparker]

Which SIGs would this impact? All of them (outside of collector?)

[zeitlinger]

Which SIGs would this impact? All of them (outside of collector?)

yes, all language sigs

[pellared]

@zeitlinger, I would like to have otlp in the name.

I propose to

Add otlpstdout, otlpstderr, otlpfile to known values of OTEL_TRACES_EXPORTER, OTEL_METRICS_EXPORTER, OTEL_LOGS_EXPORTER`.

Add OTLP_FILE_EXPORTER_PATH, OTLP_FILE_TRACES_EXPORTER_PATH, OTLP_FILE_METRICS_EXPORTER_PATH, OTLP_FILE_LOGS_EXPORTER_PATH which works only for otlpfile (based on https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/exporter.md#configuration-options but names have a little different convention to have the names shorter). The per-signals env vars take precedence over OTLP_FILE_EXPORTER_PATH.

[zeitlinger]

good point, so the question is

• OTLP_FILE_METRICS_EXPORTER_PATH vs. OTEL_EXPORTER_OTLP_METRICS_FILE (or _PATH)
• OTLP_FILE_EXPORTER_PATH vs. OTEL_EXPORTER_OTLP_FILE (or _PATH)

same number of chars, so I'd prefer the second, more consistent option