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Configure OpenTelemetry Console Exporter

Block: export.traces

The stdout exporter outputs flow records directly to the console (standard output), providing immediate, human-readable visibility into the data Mermin is processing. While OTLP export is the standard for production observability, the stdout exporter is ideal for development, debugging, and verifying flow capture without requiring an external backend.

Configuration

A complete configuration example can be found in the Default Configuration.

export.traces block

  • stdout attribute

    Output format for stdout exporter. In HCL you can use the shorthand stdout = "text_indent" or the object form stdout = { format = "text_indent" }. In YAML use the object form with a format key.

    Type: String (enum), object with format key, or null

    Default: null (disabled)

    Valid Values:

    • "text_indent": Human-readable, indented text format (recommended)

    • null: Disable stdout export

    Syntax Variations: The exporter supports both a shorthand string and a structured object format to maintain compatibility across HCL and YAML.

    • HCL Shorthand (Recommended)

      export "traces" {
  stdout = "text_indent"
}

    • Object Form (Required for YAML)

      export "traces" {
  stdout = {
    format = "text_indent"
  }
}

Output Format

Text Indent Format

The text_indent format provides structured, readable output:

Troubleshooting

No Output Visible

Symptoms: Stdout exporter enabled but no flow records in logs

Solutions:

  1. Verify stdout is set (e.g. stdout = "text_indent" or stdout = { format = "text_indent" })

  2. Check log level includes info: log_level = "info"

  3. Verify flows are being captured: check metrics

  4. Confirm log output destination

Too Much Output

Symptoms: Logs filling up quickly, hard to read

Solutions:

  1. Add flow filters (see Filtering)

  2. Reduce monitored interfaces

  3. Use grep to filter relevant flows

  4. Disable stdout after debugging

Output Format Issues

Symptoms: Truncated or malformed output

Solutions:

  1. Check log collection limits

  2. Verify container logs aren't being truncated

  3. Increase log line length limits if needed

Best Practices

  1. Disable in production: Use OTLP for production environments

  2. Enable temporarily: Turn on only when needed for debugging

  3. Use with filters: Combine with flow filters to reduce volume

  4. Document usage: Note when/why stdout is enabled

Next Steps

  1. Configure OTLP Export: Send flows to your production backend

  2. Connect to Your Backend: Grafana, Elastic, Jaeger, and more

  1. Filter Flows Before Export: Reduce console output volume

  2. Configure Log Levels: Control verbosity

Need Help?

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