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Sample logs consistently with trace sampling #6814

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Sample logs consistently with trace sampling #6814

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36 changes: 21 additions & 15 deletions sdk/logs/src/main/java/io/opentelemetry/sdk/logs/SdkLogRecordBuilder.java
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@
import io.opentelemetry.api.logs.LogRecordBuilder;
import io.opentelemetry.api.logs.Severity;
import io.opentelemetry.api.trace.Span;
import io.opentelemetry.api.trace.SpanContext;
import io.opentelemetry.api.trace.TraceFlags;
import io.opentelemetry.context.Context;
import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
import io.opentelemetry.sdk.internal.AttributesMap;
Expand Down Expand Up @@ -119,20 +121,24 @@ public void emit() {
this.observedTimestampEpochNanos == 0
? this.loggerSharedState.getClock().now()
: this.observedTimestampEpochNanos;
loggerSharedState
.getLogRecordProcessor()
.onEmit(
context,
SdkReadWriteLogRecord.create(
loggerSharedState.getLogLimits(),
loggerSharedState.getResource(),
instrumentationScopeInfo,
timestampEpochNanos,
observedTimestampEpochNanos,
Span.fromContext(context).getSpanContext(),
severity,
severityText,
body,
attributes));
SpanContext spanContext = Span.fromContext(context).getSpanContext();
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This whole thing needs to be configurable.

For an approach consistent with tracing (which I think is a good baseline to consider), we need a new LogSampler interface analagous to Sampler.

The key should sample method might have a contract like:

boolean shouldSample(
      Context context,
      Severity severity,
      Value<?> body,
      Attributes attributes);

Notes:

  • Pass individual components of LogRecord instead of SdkReadWriteLogRecord so we can avoid allocations if shouldSample returns false. Also for consistency with tracing.
  • Omit resource, scope arguments for consistency with tracing
  • Omit timestamp, observed timesamp arguments for consistency with tracing
  • Omit severityText because it mostly duplicates severity
  • Return a boolean instead of the SamplingResult returned by tracing because log sampling is less complicated that trace sampling

With an interface like this, we could have built in samplers for common use cases. I.e. we could have a "trace based" sampler that retains logs if the span in context is sampled.

TraceFlags traceFlags = spanContext.getTraceFlags();
if (!traceFlags.isSampled()) {
loggerSharedState
.getLogRecordProcessor()
.onEmit(
context,
SdkReadWriteLogRecord.create(
loggerSharedState.getLogLimits(),
loggerSharedState.getResource(),
instrumentationScopeInfo,
timestampEpochNanos,
observedTimestampEpochNanos,
spanContext,
severity,
severityText,
body,
attributes));
}
}
}
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