Add severity-based and trace-based log record processors

specification/logs/sdk.md

@@ -36,6 +36,8 @@ weight: 3
   * [Built-in processors](#built-in-processors)
     + [Simple processor](#simple-processor)
     + [Batching processor](#batching-processor)
+    + [Severity filter](#severity-filter)
+    + [Trace based filter](#trace-based-filter)
 - [LogRecordExporter](#logrecordexporter)
   * [LogRecordExporter operations](#logrecordexporter-operations)
     + [Export](#export)
@@ -456,6 +458,10 @@ make the flush timeout configurable.
 The standard OpenTelemetry SDK MUST implement both simple and batch processors,
 as described below.
 
+**Status**: [Development](../document-status.md) - The SDK SHOULD implement the
+[severity filter](#severity-filter) and [trace based filter](#trace-based-filter),
+as described below.
+
 Other common processing scenarios SHOULD be first considered
 for implementation out-of-process
 in [OpenTelemetry Collector](../overview.md#collector).
@@ -495,6 +501,65 @@ to make sure that they are not invoked concurrently.
 * `maxExportBatchSize` - the maximum batch size of every export. It must be
   smaller or equal to `maxQueueSize`. The default value is `512`.
 
+#### Severity filter
+
+**Status**: [Development](../document-status.md)
+
+This processor wraps another processor (such as the
+[batching processor](#batching-processor)) to filter log records
+based on their [SeverityNumber](./data-model.md#field-severitynumber).
+
+See the [supplementary guidelines](./supplementary-guidelines.md#filtering)
+for an implementation example.
+
+**Required operations:**
+
+* [`Enabled`](#enabled-1) - MUST forward to the delegate if the
+  [`SeverityNumber`](./data-model.md#field-severitynumber) is unspecified (`0`)
+  or greater than or equal to the configured `severity` (returning `true` in
+  this case if the delegate does not implement the optional `Enabled`
+  operation). Otherwise, MUST return `false`.
+* [`OnEmit`](#onemit) - MUST forward to the delegate if the
+  [`SeverityNumber`](./data-model.md#field-severitynumber) is unspecified (`0`)
+  or greater than or equal to the configured `severity`.
+  Otherwise, MUST NOT forward to the delegate.
+* [`Shutdown`](#shutdown) - MUST forward to the delegate.
+* [`ForceFlush`](#forceflush-1) - MUST forward to the delegate.
+
+**Configurable parameters:**
+
+* `severity` - The minimum severity level required for log records to be
+  passed to the delegate processor.
+* `delegate` - The processor to delegate to for log records that pass
+  the severity filter.
+
+#### Trace based filter
+
+**Status**: [Development](../document-status.md)
+
+This processor wraps another processor (such as the
+[batching processor](#batching-processor)) to filter log records
+based on their associated [trace sampling flag](./data-model.md#field-traceflags).
+
+**Required operations:**
+
+* [`Enabled`](#enabled-1) - MUST forward to the delegate if the
+  [`TraceFlags`](./data-model.md#field-traceflags) SAMPLED flag is set or
+  the [`SpanId`](./data-model.md#field-spanid) is not present (returning `true`
+  in this case if the delegate does not implement the optional `Enabled`
+  operation). Otherwise, MUST return `false`.
+* [`OnEmit`](#onemit) - MUST forward to the delegate if the
+  [`TraceFlags`](./data-model.md#field-traceflags) SAMPLED flag is set or
+  the [`SpanId`](./data-model.md#field-spanid) is not present.
+  Otherwise, MUST NOT forward to the delegate.
+* [`Shutdown`](#shutdown) - MUST forward to the delegate.
+* [`ForceFlush`](#forceflush-1) - MUST forward to the delegate.
+
+**Configurable parameters:**
+
+* `delegate` - The processor to delegate to for log records that pass
+  the trace-based filter.
+
 ## LogRecordExporter
 
 `LogRecordExporter` defines the interface that protocol-specific exporters must

specification/logs/supplementary-guidelines.md

@@ -195,18 +195,18 @@ type SeverityProcessor struct {
 }
 
 // OnEmit passes ctx and record to the wrapped sdklog.Processor
-// if the record's severity is greater than or equal to p.Min.
+// if the record's severity is greater than or equal to p.Min, or if the severity is 0 (unspecified).
 // Otherwise, the record is dropped (the wrapped processor is not invoked).
 func (p *SeverityProcessor) OnEmit(ctx context.Context, record *sdklog.Record) error {
-	if record.Severity() < p.Min {
+	if record.Severity() < p.Min && record.Severity() != 0 {
 		return nil
 	}
 	return p.Processor.OnEmit(ctx, record)
 }
 
-// Enabled returns false if the severity is lower than p.Min.
+// Enabled returns false if the severity is lower than p.Min and is not 0 (unspecified).
 func (p *SeverityProcessor) Enabled(ctx context.Context, param sdklog.EnabledParameters) bool {
-	if param.Severity < p.Min {
+	if param.Severity < p.Min && param.Severity != 0 {
 		return false
 	}
 	if fp, ok := p.Processor.(sdklog.FilterProcessor); ok {