[Draft] extract resource from spans

processor/spanmetricsprocessor/README.md

@@ -31,11 +31,13 @@ promexample_latency_bucket{http_method="GET",http_status_code="200",label1="valu
 ```
 
 Each metric will have _at least_ the following dimensions because they are common across all spans:
-- Service name
 - Operation
 - Span kind
 - Status code
 
+Each metric will have _at least_ the following resource attributes because they are common across all spans:
+- Service name
+
 This processor lets traces to continue through the pipeline unmodified.
 
 The following settings are required:
@@ -48,6 +50,8 @@ The following settings can be optionally configured:
   - Default: `[2ms, 4ms, 6ms, 8ms, 10ms, 50ms, 100ms, 200ms, 400ms, 800ms, 1s, 1400ms, 2s, 5s, 10s, 15s]`
 - `dimensions`: the list of dimensions to add together with the default dimensions defined above. Each additional dimension is defined with a `name` which is looked up in the span's collection of attributes. If the `name`d attribute is missing in the span, the optional provided `default` is used. If no `default` is provided, this dimension will be **omitted** from the metric.
 
+- `resource_attributes`: the list of resource attributes to add together with the default resource attributes defined above. Each additional resource attributes is defined with a `name` which is looked up in the span's collection of resource attributes. If the `name`d resource attribute is missing in the span, the optional provided `default` is used. If no `default` is provided, this resource attribute will be **omitted** from the metric.
+
 ## Examples
 
 The following is a simple example usage of the spanmetrics processor.

processor/spanmetricsprocessor/config.go

@@ -38,11 +38,17 @@ type Config struct {
 	LatencyHistogramBuckets []time.Duration `mapstructure:"latency_histogram_buckets"`
 
 	// Dimensions defines the list of additional dimensions on top of the provided:
-	// - service.name
 	// - operation
 	// - span.kind
 	// - status.code
 	// The dimensions will be fetched from the span's attributes. Examples of some conventionally used attributes:
 	// https://github.com/open-telemetry/opentelemetry-collector/blob/main/translator/conventions/opentelemetry.go.
 	Dimensions []Dimension `mapstructure:"dimensions"`
+
+	// ResourceAttributes defines the list of additional resource attributes to attach to metrics on top of the provided:
+	// - service.name
+	// These will be fetched from the span's resource attributes. For more details, see:
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/sdk.md
+	// and https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/semantic_conventions/README.md.
+	ResourceAttributes []Dimension `mapstructure:"resource_attributes"`
 }