sdk/log: Implement Record (#5073)

sdk/log/record.go

@@ -4,6 +4,7 @@
 package log // import "go.opentelemetry.io/otel/sdk/log"
 
 import (
+	"slices"
 	"time"
 
 	"go.opentelemetry.io/otel/log"
@@ -12,130 +13,197 @@ import (
 	"go.opentelemetry.io/otel/trace"
 )
 
+// attributesInlineCount is the number of attributes that are efficiently
+// stored in an array within a Record. This value is borrowed from slog which
+// performed a quantitative survey of log library use and found this value to
+// cover 95% of all use-cases (https://go.dev/blog/slog#performance).
+const attributesInlineCount = 5
+
 // Record is a log record emitted by the Logger.
-type Record struct{}
+type Record struct {
+	// Do not embed the log.Record. Attributes need to be overwrite-able and
+	// deep-copying needs to be possible.
+
+	timestamp         time.Time
+	observedTimestamp time.Time
+	severity          log.Severity
+	severityText      string
+	body              log.Value
+
+	// The fields below are for optimizing the implementation of Attributes and
+	// AddAttributes. This design is borrowed from the slog Record type:
+	// https://cs.opensource.google/go/go/+/refs/tags/go1.22.0:src/log/slog/record.go;l=20
+
+	// Allocation optimization: an inline array sized to hold
+	// the majority of log calls (based on examination of open-source
+	// code). It holds the start of the list of attributes.
+	front [attributesInlineCount]log.KeyValue
+
+	// The number of attributes in front.
+	nFront int
+
+	// The list of attributes except for those in front.
+	// Invariants:
+	//   - len(back) > 0 if nFront == len(front)
+	//   - Unused array elements are zero-ed. Used to detect mistakes.
+	back []log.KeyValue
+
+	traceID    trace.TraceID
+	spanID     trace.SpanID
+	traceFlags trace.TraceFlags
+
+	// resource represents the entity that collected the log.
+	resource *resource.Resource
+
+	// scope is the Scope that the Logger was created with.
+	scope *instrumentation.Scope
+
+	attributeValueLengthLimit int
+	attributeCountLimit       int
+}
 
 // Timestamp returns the time when the log record occurred.
 func (r *Record) Timestamp() time.Time {
-	// TODO (#5064): Implement.
-	return time.Time{}
+	return r.timestamp
 }
 
 // SetTimestamp sets the time when the log record occurred.
 func (r *Record) SetTimestamp(t time.Time) {
-	// TODO (#5064): Implement.
+	r.timestamp = t
 }
 
 // ObservedTimestamp returns the time when the log record was observed.
 func (r *Record) ObservedTimestamp() time.Time {
-	// TODO (#5064): Implement.
-	return time.Time{}
+	return r.observedTimestamp
 }
 
 // SetObservedTimestamp sets the time when the log record was observed.
 func (r *Record) SetObservedTimestamp(t time.Time) {
-	// TODO (#5064): Implement.
+	r.observedTimestamp = t
 }
 
 // Severity returns the severity of the log record.
 func (r *Record) Severity() log.Severity {
-	// TODO (#5064): Implement.
-	return log.Severity(0)
+	return r.severity
 }
 
 // SetSeverity sets the severity level of the log record.
 func (r *Record) SetSeverity(level log.Severity) {
-	// TODO (#5064): Implement.
+	r.severity = level
 }
 
 // SeverityText returns severity (also known as log level) text. This is the
 // original string representation of the severity as it is known at the source.
 func (r *Record) SeverityText() string {
-	// TODO (#5064): Implement.
-	return ""
+	return r.severityText
 }
 
 // SetSeverityText sets severity (also known as log level) text. This is the
 // original string representation of the severity as it is known at the source.
 func (r *Record) SetSeverityText(text string) {
-	// TODO (#5064): Implement.
+	r.severityText = text
 }
 
 // Body returns the body of the log record.
 func (r *Record) Body() log.Value {
-	// TODO (#5064): Implement.
-	return log.Value{}
+	return r.body
 }
 
 // SetBody sets the body of the log record.
 func (r *Record) SetBody(v log.Value) {
-	// TODO (#5064): Implement.
+	r.body = v
 }
 
 // WalkAttributes walks all attributes the log record holds by calling f for
 // each on each [log.KeyValue] in the [Record]. Iteration stops if f returns false.
 func (r *Record) WalkAttributes(f func(log.KeyValue) bool) {
-	// TODO (#5064): Implement.
+	for i := 0; i < r.nFront; i++ {
+		if !f(r.front[i]) {
+			return
+		}
+	}
+	for _, a := range r.back {
+		if !f(a) {
+			return
+		}
+	}
 }
 
 // AddAttributes adds attributes to the log record.
 func (r *Record) AddAttributes(attrs ...log.KeyValue) {
-	// TODO (#5064): Implement.
+	var i int
+	for i = 0; i < len(attrs) && r.nFront < len(r.front); i++ {
+		a := attrs[i]
+		r.front[r.nFront] = a
+		r.nFront++
+	}
+
+	r.back = slices.Grow(r.back, len(attrs[i:]))
+	r.back = append(r.back, attrs[i:]...)
 }
 
 // SetAttributes sets (and overrides) attributes to the log record.
 func (r *Record) SetAttributes(attrs ...log.KeyValue) {
-	// TODO (#5064): Implement.
+	r.nFront = 0
+	var i int
+	for i = 0; i < len(attrs) && r.nFront < len(r.front); i++ {
+		a := attrs[i]
+		r.front[r.nFront] = a
+		r.nFront++
+	}
+
+	r.back = slices.Clone(attrs[i:])
 }
 
 // AttributesLen returns the number of attributes in the log record.
 func (r *Record) AttributesLen() int {
-	// TODO (#5064): Implement.
-	return 0
+	return r.nFront + len(r.back)
 }
 
 // TraceID returns the trace ID or empty array.
 func (r *Record) TraceID() trace.TraceID {
-	// TODO (#5064): Implement.
-	return trace.TraceID{}
+	return r.traceID
 }
 
 // SetTraceID sets the trace ID.
 func (r *Record) SetTraceID(id trace.TraceID) {
-	// TODO (#5064): Implement.
+	r.traceID = id
 }
 
 // SpanID returns the span ID or empty array.
 func (r *Record) SpanID() trace.SpanID {
-	// TODO (#5064): Implement.
-	return trace.SpanID{}
+	return r.spanID
 }
 
 // SetSpanID sets the span ID.
 func (r *Record) SetSpanID(id trace.SpanID) {
-	// TODO (#5064): Implement.
+	r.spanID = id
 }
 
 // TraceFlags returns the trace flags.
 func (r *Record) TraceFlags() trace.TraceFlags {
-	return 0
+	return r.traceFlags
 }
 
 // SetTraceFlags sets the trace flags.
 func (r *Record) SetTraceFlags(flags trace.TraceFlags) {
-	// TODO (#5064): Implement.
+	r.traceFlags = flags
 }
 
 // Resource returns the entity that collected the log.
 func (r *Record) Resource() resource.Resource {
-	// TODO (#5064): Implement.
-	return resource.Resource{}
+	if r.resource == nil {
+		return *resource.Empty()
+	}
+	return *r.resource
 }
 
 // InstrumentationScope returns the scope that the Logger was created with.
 func (r *Record) InstrumentationScope() instrumentation.Scope {
-	// TODO (#5064): Implement.
-	return instrumentation.Scope{}
+	if r.scope == nil {
+		return instrumentation.Scope{}
+	}
+	return *r.scope
 }
 
 // AttributeValueLengthLimit is the maximum allowed attribute value length.
@@ -145,8 +213,7 @@ func (r *Record) InstrumentationScope() instrumentation.Scope {
 //
 // Negative value means no limit should be applied.
 func (r *Record) AttributeValueLengthLimit() int {
-	// TODO (#5064): Implement.
-	return 0
+	return r.attributeValueLengthLimit
 }
 
 // AttributeCountLimit is the maximum allowed log record attribute count. Any
@@ -156,13 +223,13 @@ func (r *Record) AttributeValueLengthLimit() int {
 //
 // Negative value means no limit should be applied.
 func (r *Record) AttributeCountLimit() int {
-	// TODO (#5064): Implement.
-	return 0
+	return r.attributeCountLimit
 }
 
 // Clone returns a copy of the record with no shared state. The original record
 // and the clone can both be modified without interfering with each other.
 func (r *Record) Clone() Record {
-	// TODO (#5064): Implement.
-	return *r
+	res := *r
+	res.back = slices.Clone(r.back)
+	return res
 }