Connecting Java Logs and Traces

Connecting Java Logs and Traces

Before you begin

Ensure log collection is configured. See Java Log Collection for Log4j, Log4j 2, or Logback instructions.

Automatic injection

Starting in version 0.74.0, the Java tracer automatically injects trace correlation identifiers into logs. For earlier versions, enable automatic injection in the Java tracer by adding dd.logs.injection=true as a system property, or through the environment variable DD_LOGS_INJECTION=true. Full configuration details can be found on the Java tracer configuration page.

Note: If the attribute.path for your trace ID is not dd.trace_id, ensure that your trace ID reserved attribute settings account for the attribute.path. For more information, see the FAQ on this topic.

Manual injection

If you prefer to manually correlate your traces with your logs, use the Java tracer’s API to retrieve correlation identifiers. Use CorrelationIdentifier.getTraceId and CorrelationIdentifier.getSpanId methods to inject identifiers at the beginning of the span being logged, and remove the identifiers when the span is complete.

import org.apache.logging.log4j.ThreadContext;
import datadog.trace.api.CorrelationIdentifier;

// There must be spans started and active before this block.
try {
    ThreadContext.put("dd.trace_id", CorrelationIdentifier.getTraceId());
    ThreadContext.put("dd.span_id", CorrelationIdentifier.getSpanId());

// Log something

} finally {
    ThreadContext.remove("dd.trace_id");
    ThreadContext.remove("dd.span_id");
}
import org.slf4j.MDC;
import datadog.trace.api.CorrelationIdentifier;

// There must be spans started and active before this block.
try {
    MDC.put("dd.trace_id", CorrelationIdentifier.getTraceId());
    MDC.put("dd.span_id", CorrelationIdentifier.getSpanId());

// Log something

} finally {
    MDC.remove("dd.trace_id");
    MDC.remove("dd.span_id");
}

Note: If you are not using a Datadog Log Integration to parse your logs, custom log parsing rules need to ensure that dd.trace_id and dd.span_id are being parsed as strings. For more information, see the FAQ on this topic.

See the Java log collection documentation for more details about specific logger implementation and instructions for logging in JSON format.

Further Reading