O11Y-1631: add SpanLimits, implement maxNumAttributes and maxNumAttributeLength

lib/sdk.dart

@@ -26,3 +26,4 @@ export 'src/sdk/trace/span_processors/simple_processor.dart'
 export 'src/sdk/trace/tracer.dart' show Tracer;
 export 'src/sdk/trace/tracer_provider.dart' show TracerProvider;
 export 'src/sdk/trace/trace_state.dart' show TraceState;
+export 'src/sdk/trace/span_limits.dart' show SpanLimits;

lib/src/api/common/attribute.dart

@@ -4,27 +4,59 @@ class Attribute {
   final Object value;
 
   /// Create an Attribute from a String value.
-  Attribute.fromString(this.key, String this.value);
+  Attribute.fromString(this.key, String this.value) {
+    if (key == null) {
+      throw ArgumentError("key can't be null.");
+    }
+  }
 
   /// Create an Attribute from a boolean value.
   // ignore: avoid_positional_boolean_parameters
-  Attribute.fromBoolean(this.key, bool this.value);
+  Attribute.fromBoolean(this.key, bool this.value) {
+    if (key == null) {
+      throw ArgumentError("key can't be null.");
+    }
+  }
 
   /// Create an Attribute from a double-precision floating-point value.
-  Attribute.fromDouble(this.key, double this.value);
+  Attribute.fromDouble(this.key, double this.value) {
+    if (key == null) {
+      throw ArgumentError("key can't be null.");
+    }
+  }
 
   /// Create an Attribute from an integer value.
-  Attribute.fromInt(this.key, int this.value);
+  Attribute.fromInt(this.key, int this.value) {
+    if (key == null) {
+      throw ArgumentError("key can't be null.");
+    }
+  }
 
   /// Create an Attribute from a list of String values.
-  Attribute.fromStringList(this.key, List<String> this.value);
+  Attribute.fromStringList(this.key, List<String> this.value) {
+    if (key == null) {
+      throw ArgumentError("key can't be null.");
+    }
+  }
 
   /// Create an Attribute from a list of boolean values.
-  Attribute.fromBooleanList(this.key, List<bool> this.value);
+  Attribute.fromBooleanList(this.key, List<bool> this.value) {
+    if (key == null) {
+      throw ArgumentError("key can't be null.");
+    }
+  }
 
   /// Create an Attribute from a list of double-precision floating-point values.
-  Attribute.fromDoubleList(this.key, List<double> this.value);
+  Attribute.fromDoubleList(this.key, List<double> this.value) {
+    if (key == null) {
+      throw ArgumentError("key can't be null.");
+    }
+  }
 
   /// Create an Attribute from a list of integer values.
-  Attribute.fromIntList(this.key, List<int> this.value);
+  Attribute.fromIntList(this.key, List<int> this.value) {
+    if (key == null) {
+      throw ArgumentError("key can't be null.");
+    }
+  }
 }

lib/src/api/common/attributes.dart

@@ -12,6 +12,9 @@ class Attributes {
   /// Retrieve the value associated with the Attribute with key [key].
   Object get(String key) => _attributes[key];
 
+  ///
+  int get length => _attributes.length;
+
   /// Retrieve the keys of all Attributes in this collection.
   Iterable<String> get keys => _attributes.keys;
 

lib/src/api/trace/nonrecording_span.dart

@@ -10,24 +10,19 @@ import '../../../api.dart' as api;
 /// This class should not be exposed to consumers and is used internally to wrap
 /// [api.SpanContext] being injected or extracted for external calls.
 class NonRecordingSpan implements api.Span {
-  final api.Attributes _attributes = api.Attributes.empty();
   final api.SpanStatus _status = api.SpanStatus()..code = api.StatusCode.ok;
   final api.SpanContext _spanContext;
 
   NonRecordingSpan(this._spanContext);
 
   @override
-  api.Attributes get attributes => _attributes;
+  void setAttribute(api.Attribute attribute) {}
 
   @override
-  set attributes(api.Attributes attributes) {
-    return;
-  }
+  void setAttributes(List<api.Attribute> attributes) {}
 
   @override
-  void end() {
-    return;
-  }
+  void end() {}
 
   @override
   Int64 get endTime => null;
@@ -42,9 +37,7 @@ class NonRecordingSpan implements api.Span {
   api.SpanId get parentSpanId => api.SpanId.invalid();
 
   @override
-  void setStatus(api.StatusCode status, {String description}) {
-    return;
-  }
+  void setStatus(api.StatusCode status, {String description}) {}
 
   @override
   api.SpanContext get spanContext => _spanContext;

lib/src/api/trace/noop_tracer.dart

@@ -6,7 +6,7 @@ import '../../../sdk.dart' as sdk;
 class NoopTracer implements api.Tracer {
   @override
   api.Span startSpan(String name,
-      {api.Context context, api.Attributes attributes}) {
+      {api.Context context, List<api.Attribute> attributes}) {
     final parentContext = context.spanContext;
 
     return api.NonRecordingSpan(

lib/src/api/trace/sampler.dart

@@ -8,7 +8,7 @@ abstract class Sampler {
       api.TraceId traceId,
       String spanName,
       bool spanIsRemote, // ignore: avoid_positional_boolean_parameters
-      api.Attributes spanAttributes);
+      List<api.Attribute> spanAttributes);
 
   String get description;
 }

lib/src/api/trace/sampling_result.dart

@@ -10,7 +10,7 @@ enum Decision {
 /// be processed for collection.
 abstract class SamplingResult {
   final api.Decision decision;
-  final api.Attributes spanAttributes;
+  final List<api.Attribute> spanAttributes;
   final api.TraceState traceState;
 
   SamplingResult(this.decision, this.spanAttributes, this.traceState);

lib/src/api/trace/span.dart

@@ -44,11 +44,11 @@ abstract class Span {
   /// Retrieve the status of the [Span].
   api.SpanStatus get status;
 
-  /// Set metadata to be included on this span.
-  set attributes(api.Attributes attributes);
+  /// set single attribute
+  void setAttribute(api.Attribute attribute);
 
-  /// Retrieve metadata included on this span.
-  api.Attributes get attributes;
+  /// set multiple attributes
+  void setAttributes(List<api.Attribute> attributes);
 
   /// Retrieve the resource on this span.
   api.Resource get resource;

lib/src/api/trace/tracer.dart

@@ -8,5 +8,5 @@ abstract class Tracer {
   /// Starts a new [api.Span] without setting it as the current span in this
   /// tracer's context.
   api.Span startSpan(String name,
-      {api.Context context, api.Attributes attributes});
+      {api.Context context, List<api.Attribute> attributes});
 }

lib/src/sdk/trace/exporters/collector_exporter.dart

@@ -6,6 +6,7 @@ import 'opentelemetry/proto/collector/trace/v1/trace_service.pb.dart'
 import 'opentelemetry/proto/trace/v1/trace.pb.dart' as pb_trace;
 import 'opentelemetry/proto/resource/v1/resource.pb.dart' as pb_resource;
 import 'opentelemetry/proto/common/v1/common.pb.dart' as pb_common;
+import '../span.dart' as sdk;
 
 class CollectorExporter implements api.SpanExporter {
   Uri uri;
@@ -46,7 +47,7 @@ class CollectorExporter implements api.SpanExporter {
           <api.InstrumentationLibrary, List<pb_trace.Span>>{};
       il[span.instrumentationLibrary] =
           il[span.instrumentationLibrary] ?? <pb_trace.Span>[]
-            ..add(_spanToProtobuf(span));
+            ..add(_spanToProtobuf(span as sdk.Span));
       rsm[span.resource] = il;
     }
 
@@ -74,7 +75,7 @@ class CollectorExporter implements api.SpanExporter {
     return rss;
   }
 
-  pb_trace.Span _spanToProtobuf(api.Span span) {
+  pb_trace.Span _spanToProtobuf(sdk.Span span) {
     pb_trace.Status_StatusCode statusCode;
     switch (span.status.code) {
       case api.StatusCode.unset:

lib/src/sdk/trace/samplers/always_off_sampler.dart

@@ -7,7 +7,7 @@ class AlwaysOffSampler implements api.Sampler {
 
   @override
   api.SamplingResult shouldSample(api.Context context, api.TraceId traceId,
-      String spanName, bool spanIsRemote, api.Attributes spanAttributes) {
+      String spanName, bool spanIsRemote, List<api.Attribute> spanAttributes) {
     return sdk.SamplingResult(api.Decision.drop, spanAttributes,
         context.spanContext?.traceState ?? sdk.TraceState.empty());
   }

lib/src/sdk/trace/samplers/always_on_sampler.dart

@@ -1,19 +1,14 @@
-import '../../../api/common/attributes.dart';
-import '../../../api/context/context.dart';
-import '../../../api/trace/sampler.dart' as api;
-import '../../../api/trace/sampling_result.dart' as result_api;
-import '../../../api/trace/trace_id.dart';
-import '../trace_state.dart';
-import 'sampling_result.dart';
+import '../../../../api.dart' as api;
+import '../../../../sdk.dart' as sdk;
 
 class AlwaysOnSampler implements api.Sampler {
   @override
   String get description => 'AlwaysOnSampler';
 
   @override
-  result_api.SamplingResult shouldSample(Context context, TraceId traceId,
-      String spanName, bool spanIsRemote, Attributes spanAttributes) {
-    return SamplingResult(result_api.Decision.recordAndSample, spanAttributes,
-        context.spanContext?.traceState ?? TraceState.empty());
+  api.SamplingResult shouldSample(api.Context context, api.TraceId traceId,
+      String spanName, bool spanIsRemote, List<api.Attribute> spanAttributes) {
+    return sdk.SamplingResult(api.Decision.recordAndSample, spanAttributes,
+        context.spanContext?.traceState ?? sdk.TraceState.empty());
   }
 }

lib/src/sdk/trace/samplers/parent_based_sampler.dart

@@ -25,7 +25,7 @@ class ParentBasedSampler implements api.Sampler {
 
   @override
   api.SamplingResult shouldSample(api.Context context, api.TraceId traceId,
-      String spanName, bool spanIsRemote, api.Attributes spanAttributes) {
+      String spanName, bool spanIsRemote, List<api.Attribute> spanAttributes) {
     final parentSpanContext = context.spanContext;
 
     if (parentSpanContext == null || !parentSpanContext.isValid) {

lib/src/sdk/trace/samplers/sampling_result.dart

@@ -5,7 +5,7 @@ class SamplingResult implements api.SamplingResult {
   @override
   final api.Decision decision;
   @override
-  final Attributes spanAttributes;
+  final List<Attribute> spanAttributes;
   @override
   final TraceState traceState;
 

lib/src/sdk/trace/span.dart

@@ -1,6 +1,7 @@
 import 'package:fixnum/fixnum.dart';
 
 import '../../../api.dart' as api;
+import '../../../sdk.dart' as sdk;
 
 /// A representation of a single operation within a trace.
 class Span implements api.Span {
@@ -9,9 +10,12 @@ class Span implements api.Span {
   final api.SpanStatus _status = api.SpanStatus();
   final List<api.SpanProcessor> _processors;
   final api.Resource _resource;
+  sdk.SpanLimits _spanLimits = sdk.SpanLimits();
   final api.InstrumentationLibrary _instrumentationLibrary;
   Int64 _startTime;
   Int64 _endTime;
+  int _droppedSpanAttributes = 0;
+  final api.Attributes attributes = api.Attributes.empty();
 
   @override
   String name;
@@ -22,9 +26,15 @@ class Span implements api.Span {
   /// Construct a [Span].
   Span(this.name, this._spanContext, this._parentSpanId, this._processors,
       this._resource, this._instrumentationLibrary,
-      {api.Attributes attributes}) {
+      {List<api.Attribute> attributes, sdk.SpanLimits spanlimits}) {
     _startTime = Int64(DateTime.now().toUtc().microsecondsSinceEpoch);
-    this.attributes = attributes ?? api.Attributes.empty();
+
+    if (spanlimits != null) _spanLimits = spanlimits;
+
+    if (attributes != null) {
+      setAttributes(attributes);
+    }
+
     for (var i = 0; i < _processors.length; i++) {
       _processors[i].onStart();
     }
@@ -77,16 +87,73 @@ class Span implements api.Span {
       _instrumentationLibrary;
 
   @override
-  api.Attributes attributes;
+  void setAttributes(List<api.Attribute> attributes) {
+    //Don't want to have any attribute
+    if (_spanLimits.maxNumAttributes == 0) {
+      _droppedSpanAttributes += attributes.length;
+      return;
+    }
+
+    attributes.forEach(setAttribute);
+  }
+
+  @override
+  void setAttribute(api.Attribute attribute) {
+    //Don't want to have any attribute
+    if (_spanLimits.maxNumAttributes == 0) {
+      _droppedSpanAttributes++;
+      return;
+    }
+
+    final obj = attributes.get(attribute.key);
+    //If current attributes.length is equal or greater than maxNumAttributes and
+    //key is not in current map, drop it.
+    if (attributes.length >= _spanLimits.maxNumAttributes && obj == null) {
+      _droppedSpanAttributes++;
+      return;
+    }
+    attributes.add(_rebuildAttribute(attribute));
+  }
+
+  /// reBuild an attribute, this way it is tightly coupled with the type we supported,
+  /// if later we added more types, then we need to change this method.
+  api.Attribute _rebuildAttribute(api.Attribute attr) {
+    //if maxNumAttributeLength is less than zero, then it has unlimited length.
+    if (_spanLimits.maxNumAttributeLength < 0) return attr;
+
+    if (attr.value is String) {
+      attr = api.Attribute.fromString(
+          attr.key,
+          _applyAttributeLengthLimit(
+              attr.value, _spanLimits.maxNumAttributeLength));
+    } else if (attr.value is List<String>) {
+      final listString = attr.value as List<String>;
+      for (var j = 0; j < listString.length; j++) {
+        listString[j] = _applyAttributeLengthLimit(
+            listString[j], _spanLimits.maxNumAttributeLength);
+      }
+      attr = api.Attribute.fromStringList(attr.key, listString);
+    }
+    return attr;
+  }
 
   @override
   void recordException(dynamic exception, {StackTrace stackTrace}) {
+    // ignore: todo
     // TODO: O11Y-1531: Consider integration of Events here.
     setStatus(api.StatusCode.error, description: exception.toString());
-    attributes.addAll([
+    setAttributes([
       api.Attribute.fromBoolean('error', true),
       api.Attribute.fromString('exception', exception.toString()),
       api.Attribute.fromString('stacktrace', stackTrace.toString()),
     ]);
   }
+
+  //Truncate just strings which length is longer than configuration.
+  //Reference: https://github.com/open-telemetry/opentelemetry-java/blob/14ffacd1cdd22f5aa556eeda4a569c7f144eadf2/sdk/common/src/main/java/io/opentelemetry/sdk/internal/AttributeUtil.java#L80
+  static String _applyAttributeLengthLimit(String value, int lengthLimit) {
+    return value.length > lengthLimit ? value.substring(0, lengthLimit) : value;
+  }
+
+  int get droppedAttributes => _droppedSpanAttributes;
 }