[exporter/debug] Default sending_queue size causes immediate export failures

[ahayworth]

Component(s)

exporter/debug

What happened?

Describe the bug

The default sending queue configuration added in #14101 sets the queue size to 1. With such a configuration, sending more than one log at a time to the collector causes immediate export failures, and can be reproduced easily with a basic configuration and telemetrygen with two workers.

I am not sure what the queue size should be, but it seems that 1 might be too low. 😅

Steps to reproduce

1. Run a collector with the provided sample configuration. I used docker, and ran it like so: docker run -v $(pwd)/config.yaml:/etc/otelcol/config.yaml -p 4318:4318 otel/opentelemetry-collector:0.139.0
2. Run telemetrygen with more than one worker: telemetrygen logs --duration inf --workers 2 --otlp-http --otlp-insecure --otlp-endpoint 127.0.0.1:4318

What did you expect to see?

No export failures.

What did you see instead?

Immediate export failures.

Collector version

v0.139.0

Environment information

Environment

OS: macOS Sequoia 15.6.1 (reproducible in docker, however).
Compiler(if manually compiled): n/a

OpenTelemetry Collector configuration

receivers:
  otlp:
    protocols:
      http:
        endpoint: 0.0.0.0:4318
exporters:
  debug:
service:
  pipelines:
    logs:
      receivers: [otlp]
      exporters: [debug]

Log output

2025-11-06T14:42:08.465Z        info    service@v0.139.0/service.go:222 Starting otelcol...     {"resource": {"service.instance.id": "6f29825a-fb72-4d6e-8f8e-1129c8f42d1b", "service.name": "otelcol", "service.version": "0.139.0"}, "Version": "0.139.0", "NumCPU": 14}
2025-11-06T14:42:08.465Z        info    extensions/extensions.go:40     Starting extensions...  {"resource": {"service.instance.id": "6f29825a-fb72-4d6e-8f8e-1129c8f42d1b", "service.name": "otelcol", "service.version": "0.139.0"}}
2025-11-06T14:42:08.465Z        info    otlpreceiver@v0.139.0/otlp.go:178       Starting HTTP server    {"resource": {"service.instance.id": "6f29825a-fb72-4d6e-8f8e-1129c8f42d1b", "service.name": "otelcol", "service.version": "0.139.0"}, "otelcol.component.id": "otlp", "otelcol.component.kind": "receiver", "endpoint": "[::]:4318"}
2025-11-06T14:42:08.465Z        info    service@v0.139.0/service.go:245 Everything is ready. Begin running and processing data. {"resource": {"service.instance.id": "6f29825a-fb72-4d6e-8f8e-1129c8f42d1b", "service.name": "otelcol", "service.version": "0.139.0"}}
2025-11-06T14:42:10.542Z        info    Logs    {"resource": {"service.instance.id": "6f29825a-fb72-4d6e-8f8e-1129c8f42d1b", "service.name": "otelcol", "service.version": "0.139.0"}, "otelcol.component.id": "debug", "otelcol.component.kind": "exporter", "otelcol.signal": "logs", "resource logs": 1, "log records": 1}
2025-11-06T14:42:10.542Z        error   internal/base_exporter.go:114   Exporting failed. Rejecting data.       {"resource": {"service.instance.id": "6f29825a-fb72-4d6e-8f8e-1129c8f42d1b", "service.name": "otelcol", "service.version": "0.139.0"}, "otelcol.component.id": "debug", "otelcol.component.kind": "exporter", "otelcol.signal": "logs", "error": "sending queue is full", "rejected_items": 1}

Additional context

No response

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[github-actions]

Pinging code owners:

• exporter/debug: @andrzej-stencel

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[axw]

@andrzej-stencel @codeboten should we update the debug exporter to set block_on_overflow: true by default? Alternatively, use the default queue size of 1000 as documented at https://github.com/open-telemetry/opentelemetry-collector/tree/main/exporter/exporterhelper, and if anyone sends more than that they can explicitly turn on block_on_overflow?

[VihasMakwana]

I'm wondering we there's a reason why we set queue size to 1?

I like the second option i.e. to use default queue config, with size 1000. Exporter generally just use exporterhelper.NewDefaultQueueConfig() and don't modify the values.

[andrzej-stencel]

As a workaround, set sending_queue::enabled to false.

exporters:
  debug:
    sending_queue:
      enabled: false

[andrzej-stencel]

Why have the sending queue enabled by default on the Debug exporter? I think it makes sense for the Debug exporter to have the sending queue disabled by default. Users can always choose to enable it (now that it is actually possible, thanks @codeboten for your work!).

Here's a PR implementing this: #14151