Correlate traces and logs ¶

This guide explains how to correlate traces with logs in Grafana Tempo. When set up correctly, clicking a trace shows the associated logs — and clicking a log line links back to its trace.

Prerequisites ¶

Auto-instrumentation enabled (or manual OTel SDK setup)
Logs sent to Grafana Loki

How it works ¶

The OTel Java agent automatically injects trace_id and span_id into your logging framework's MDC (Mapped Diagnostic Context). If your log output includes MDC fields, correlation works out of the box — no extra dependencies needed.

Most Nav apps already have this working. If you use LogstashEncoder (which outputs all MDC fields as JSON), trace context is already in your logs.

Verify it works ¶

Open Nais APM and find a trace for your service
Click "View logs" — if correlated logs appear, you're done

If logs don't appear, check the troubleshooting section below.

Log format requirements ¶

If you use LogstashEncoder, all MDC fields (including trace_id and span_id) are included automatically:

xml

<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <encoder class="net.logstash.logback.encoder.LogstashEncoder" />
</appender>

No extra dependencies or appender wrapping needed when using auto-instrumentation.

If you use a plain PatternLayout, add %X{trace_id} and %X{span_id} to your pattern:

xml

<pattern>%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} traceId=%X{trace_id} spanId=%X{span_id} - %msg%n</pattern>

Log4j2 context data injection is automatic with the OTel agent. Use %X{trace_id} in your pattern:

xml

<PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} traceId: %X{trace_id} spanId: %X{span_id} - %msg%n" />

Correlation is automatic with Node.js auto-instrumentation. The trace and span IDs are included in logs without extra config.

If you use Next.js, add the packages to serverExternalPackages to prevent tree-shaking:

javascript

// next.config.js
module.exports = {
  serverExternalPackages: ['@navikt/pino-logger', 'pino'],
};

Correlation is automatic with Node.js auto-instrumentation.

Add to serverExternalPackages:

javascript

// next.config.js
module.exports = {
  serverExternalPackages: ['@navikt/next-logger', 'pino'],
};

Without auto-instrumentation ¶

If your app does not use Nais auto-instrumentation, you need to inject trace context into MDC manually. Add the OpenTelemetry logback appender:

Plaintext

io.opentelemetry.instrumentation:opentelemetry-logback-mdc-1.0:2.16.0-alpha

xml

<appender name="OTEL" class="io.opentelemetry.instrumentation.logback.mdc.v1_0.OpenTelemetryAppender">
    <appender-ref ref="STDOUT" />
</appender>

<root level="INFO">
    <appender-ref ref="OTEL" />
</root>

Troubleshooting ¶

If trace-log correlation isn't working:

Check your logs contain trace_id — query Loki for your app and look for the field
Verify auto-instrumentation is enabled — check your nais.yaml has autoInstrumentation.enabled: true
Check LogstashEncoder — if you use a custom pattern, make sure %X{trace_id} is included

Result ¶

When correlation works, Grafana Tempo shows associated logs inline with your trace:

Correlate traces and logs