Add Span.updateAttributes (apple#133)

Author: adam-fowler

Sources/Tracing/SpanProtocol.swift

@@ -161,6 +161,23 @@ extension Span {
     }
 }
 
+extension Span {
+    /// Update Span attributes in a block instead of individually.
+    ///
+    /// Updating a span attribute will involve some type of thread synchronisation
+    /// primitive to avoid multiple threads updating the attributes at the same
+    /// time. If you update each attributes individually this can cause slowdown.
+    /// This function updates the attributes in one call to avoid hitting the
+    /// thread synchronisation code multiple times.
+    ///
+    /// - Parameter update: closure used to update span attributes
+    public func updateAttributes(_ update: (inout SpanAttributes) -> Void) {
+        var attributes = self.attributes
+        update(&attributes)
+        self.attributes = attributes
+    }
+}
+
 // ==== ----------------------------------------------------------------------------------------------------------------
 // MARK: Span Event
 

Tests/TracingTests/SpanTests.swift

@@ -248,6 +248,23 @@ final class SpanTests: XCTestCase {
         XCTAssertEqual(statusCode, 418)
         XCTAssertEqual(attributes.get("http.status_code"), SpanAttribute.int32(418))
     }
+
+    func testSpanUpdateAttributes() {
+        let span = TestSpan(
+            operationName: "client",
+            startTime: DefaultTracerClock.now,
+            context: ServiceContext.topLevel,
+            kind: .client,
+            onEnd: { _ in }
+        )
+        span.updateAttributes { attributes in
+            attributes.set("http.status_code", value: .int32(200))
+            attributes.set("http.method", value: .string("GET"))
+        }
+
+        XCTAssertEqual(span.attributes.get("http.status_code"), .int32(200))
+        XCTAssertEqual(span.attributes.get("http.method"), .string("GET"))
+    }
 }
 
 // ==== ----------------------------------------------------------------------------------------------------------------