Remove the need for #if TracingSupport on every trace call-site

Author: ktoso

Sources/AsyncHTTPClient/HTTPHandler.swift

@@ -929,7 +929,9 @@ extension HTTPClient {
         public let logger: Logger  // We are okay to store the logger here because a Task is for only one request.
 
         #if TracingSupport
-        public let tracer: (any Tracer)?  // We are okay to store the tracer here because a Task is for only one request.
+        let tracer: (any Tracer)?  // We are okay to store the tracer here because a Task is for only one request.
+        #else
+        let tracer: TracingSupportDisabledTracer?  // We are okay to store the tracer here because a Task is for only one request.
         #endif
 
         let promise: EventLoopPromise<Response>
@@ -965,9 +967,7 @@ extension HTTPClient {
             self.eventLoop = eventLoop
             self.promise = eventLoop.makePromise()
             self.logger = logger
-            #if TracingSupport
             self.tracer = nil
-            #endif // TracingSupport
             self.makeOrGetFileIOThreadPool = makeOrGetFileIOThreadPool
             self.state = NIOLockedValueBox(State(isCancelled: false, taskDelegate: nil))
         }

Sources/AsyncHTTPClient/RequestBag+Tracing.swift

@@ -12,17 +12,60 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if TracingSupport
-
 import Logging
 import NIOConcurrencyHelpers
 import NIOCore
 import NIOHTTP1
 import NIOSSL
 
+#if TracingSupport
 import Tracing
+#endif
+
+#if TracingSupport
+typealias HTTPClientTracingSupportTracerType = Tracer
+#else
+enum TracingSupportDisabledTracer {}
+typealias HTTPClientTracingSupportTracerType = TracingSupportDisabledTracer
+#endif
+
+protocol _TracingSupportOperations {
+    associatedtype TracerType
+
+    /// Starts the "overall" Span that encompases the beginning of a request until receipt of the head part of the response.
+    mutating func startRequestSpan(tracer: TracerType?)
+
+    /// Fails the active overall span given some internal error, e.g. timeout, pool shutdown etc.
+    /// This is not to be used for failing a span given a failure status coded HTTPResponse.
+    mutating func failRequestSpan(error: any Error)
+
+    /// Ends the active overall span upon receipt of the response head.
+    /// 
+    /// If the status code is in error range, this will automatically fail the span.
+    mutating func endRequestSpan(response: HTTPResponseHead)
+}
+
+extension RequestBag.LoopBoundState: _TracingSupportOperations { }
+
+#if !TracingSupport
+/// Operations used to start/end spans at apropriate times from the Request lifecycle.
+extension RequestBag.LoopBoundState {
+    typealias TracerType = HTTPClientTracingSupportTracerType
+
+    @inlinable
+    mutating func startRequestSpan(tracer: TracerType?) {}
+    
+    @inlinable
+    mutating func failRequestSpan(error: any Error) {}
+
+    @inlinable
+    mutating func endRequestSpan(response: HTTPResponseHead) {}
+}
+
+#else // TracingSupport
 
 extension RequestBag.LoopBoundState {
+    typealias TracerType = Tracer
 
     mutating func startRequestSpan(tracer: (any Tracer)?) {
         guard let tracer else {
@@ -33,7 +76,7 @@ extension RequestBag.LoopBoundState {
         self.activeRequestSpan = tracer.startSpan("\(request.method)")
     }
 
-    // TODO: should be able to record the reason for the failure, e.g. timeout, cancellation, server error etc
+    // TODO: should be able to record the reason for the failure, e.g. timeout, cancellation etc.
     mutating func failRequestSpan(error: any Error) { 
         guard let span = activeRequestSpan else {
             return
@@ -49,7 +92,7 @@ extension RequestBag.LoopBoundState {
             return
         }
 
-        span.attributes["http.response.status_code"] = SpanAttribute.int(Int64(response.status.code))
+        span.attributes["http.response.status_code"] = SpanAttribute.int64(Int64(response.status.code))
         if response.status.code >= 400 {
             span.setStatus(.init(code: .error))
         }

Sources/AsyncHTTPClient/RequestBag.swift

@@ -71,11 +71,9 @@ final class RequestBag<Delegate: HTTPClientResponseDelegate & Sendable>: Sendabl
         self.task.logger
     }
 
-    #if TracingSupport
-    var tracer: (any Tracer)? {
+    var tracer: HTTPClientTracingSupportTracerType? {
         self.task.tracer
     }
-    #endif
 
     let connectionDeadline: NIODeadline
 
@@ -132,24 +130,18 @@ final class RequestBag<Delegate: HTTPClientResponseDelegate & Sendable>: Sendabl
 
     private func willExecuteRequest0(_ executor: HTTPRequestExecutor) {
         // Immediately start a span for the "whole" request
-        #if TracingSupport
         self.loopBoundState.value.startRequestSpan(tracer: self.tracer)
-        #endif
 
         let action = self.loopBoundState.value.state.willExecuteRequest(executor)
         switch action {
         case .cancelExecuter(let executor):
             executor.cancelRequest(self)
-            #if TracingSupport
             self.loopBoundState.value.failRequestSpan(error: CancellationError()) // TODO: something better?
-            #endif
         case .failTaskAndCancelExecutor(let error, let executor):
             self.delegate.didReceiveError(task: self.task, error)
             self.task.failInternal(with: error)
             executor.cancelRequest(self)
-            #if TracingSupport
             self.loopBoundState.value.failRequestSpan(error: error)
-            #endif
         case .none:
             break
         }
@@ -252,9 +244,7 @@ final class RequestBag<Delegate: HTTPClientResponseDelegate & Sendable>: Sendabl
         self.task.eventLoop.assertInEventLoop()
 
         self.delegate.didReceiveError(task: self.task, error)
-        #if TracingSupport
         self.loopBoundState.value.failRequestSpan(error: error)
-        #endif // TracingSupport
         self.task.promise.fail(error)
     }
 
@@ -408,10 +398,7 @@ final class RequestBag<Delegate: HTTPClientResponseDelegate & Sendable>: Sendabl
         self.executeFailAction0(action)
 
         self.loopBoundState.value.redirectTask?.fail(reason: error)
-        
-        #if TracingSupport
         self.loopBoundState.value.failRequestSpan(error: error)
-        #endif // TracingSupport
     }
 
     private func executeFailAction0(_ action: RequestBag<Delegate>.StateMachine.FailAction) {
@@ -422,9 +409,7 @@ final class RequestBag<Delegate: HTTPClientResponseDelegate & Sendable>: Sendabl
             self.failTask0(error)
         case .cancelExecutor(let executor):
             executor.cancelRequest(self)
-            #if TracingSupport
             self.loopBoundState.value.failRequestSpan(error: CancellationError()) // TODO: is this right?
-            #endif
         case .none:
             break
         }