Merge pull request #535 from DataDog/louiszawadzki/fix-ios-flaky-test

Fix iOS tracer concurrency
DataDog · Oct 30, 2023 · a045dd7 · a045dd7
1 parent f2333b8
commit a045dd7
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Showing 2 changed files with 7 additions and 4 deletions.
diff --git a/packages/core/ios/Sources/DdTraceImplementation.swift b/packages/core/ios/Sources/DdTraceImplementation.swift
@@ -44,14 +44,13 @@ public class DdTraceImplementation: NSObject {
     public func finishSpan(spanId: NSString, context: NSDictionary, timestampMs: Double, resolve:RCTPromiseResolveBlock, reject:RCTPromiseRejectBlock) -> Void {
         objc_sync_enter(self)
         let optionalSpan = spanDictionary.removeValue(forKey: spanId)
-        objc_sync_exit(self)
-
         if let span = optionalSpan {
             set(tags: castAttributesToSwift(context).mergeWithGlobalAttributes(), to: span)
             let timeIntervalSince1970: TimeInterval = timestampMs / 1_000
             span.finish(at: Date(timeIntervalSince1970: timeIntervalSince1970))
         }
-
+        objc_sync_exit(self)
+
         resolve(nil)
     }
 

diff --git a/packages/core/ios/Tests/DdTraceTests.swift b/packages/core/ios/Tests/DdTraceTests.swift
@@ -139,6 +139,10 @@ internal class DdTraceTests: XCTestCase {
     }
 
     func testTracingConcurrently() {
+        // It is possible and acceptable that a concurrent finishSpan resolve is called on a different thread before we get the lastResolveValue.
+        // This would override lastResolveValue to be `nil`. To avoid this, we use a different resolve.
+        func mockFinishResolve(args: Any?) {}
+
         let iterationCount = 30
         DispatchQueue.concurrentPerform(iterations: iterationCount) { iteration in
             tracer.startSpan(
@@ -149,7 +153,7 @@ internal class DdTraceTests: XCTestCase {
                 reject: mockReject
             )
             let spanID = lastResolveValue as! NSString
-            tracer.finishSpan(spanId: spanID, context: testTags, timestampMs: 100, resolve: mockResolve, reject: mockReject)
+            tracer.finishSpan(spanId: spanID, context: testTags, timestampMs: 100, resolve: mockFinishResolve, reject: mockReject)
         }
 
         XCTAssertEqual(mockNativeTracer.startedSpans.count, iterationCount, "\(mockNativeTracer.startedSpans)")