Log slow API requests with server spans and client timing

2026-10-21 14:45:19 -07:00
parent 671165ec71
commit b4c1dbab37
31 changed files with 458 additions and 185 deletions
@@ -0,0 +1,41 @@
+import Foundation
+
+final class RequestTiming: NSObject, URLSessionTaskDelegate, Sendable {
+    private static let slow: TimeInterval = 0.2
+
+    func urlSession(_ session: URLSession, task: URLSessionTask, didFinishCollecting metrics: URLSessionTaskMetrics) {
+        guard let t = metrics.transactionMetrics.last, let response = t.response as? HTTPURLResponse, response.statusCode != 101, response.value(forHTTPHeaderField: "Content-Type") != "text/event-stream", let fetched = t.fetchStartDate, let sent = t.requestStartDate, let first = t.responseStartDate, let done = t.responseEndDate else {
+            return
+        }
+        let finished = Date()
+        let serverTiming = response.value(forHTTPHeaderField: "Server-Timing") ?? ""
+        let server = Self.serverTotal(serverTiming)
+        let queue = (t.connectStartDate ?? sent).timeIntervalSince(fetched)
+        let connect = t.connectStartDate.flatMap { start in t.connectEndDate.map { $0.timeIntervalSince(start) } } ?? 0
+        let network = first.timeIntervalSince(sent) - server
+        let download = done.timeIntervalSince(first)
+        let total = done.timeIntervalSince(fetched)
+        let line = "\(task.originalRequest?.httpMethod ?? "") \(task.originalRequest?.url?.path ?? "")"
+        Task { @MainActor in
+            let app = Date().timeIntervalSince(finished)
+            if total + app < Self.slow {
+                return
+            }
+            log.notice("request slow \(line, privacy: .public) total=\(Self.ms(total + app), privacy: .public) queue=\(Self.ms(queue), privacy: .public) connect=\(Self.ms(connect), privacy: .public) network=\(Self.ms(network), privacy: .public) server=\(Self.ms(server), privacy: .public) download=\(Self.ms(download), privacy: .public) app=\(Self.ms(app), privacy: .public) spans=\(serverTiming, privacy: .public)")
+        }
+    }
+
+    private static func serverTotal(_ header: String) -> TimeInterval {
+        for metric in header.split(separator: ",") {
+            let parts = metric.split(separator: ";").map { $0.trimmingCharacters(in: .whitespaces) }
+            if parts.first == "total", let dur = parts.dropFirst().first(where: { $0.hasPrefix("dur=") }), let value = Double(dur.dropFirst(4)) {
+                return value / 1000
+            }
+        }
+        return 0
+    }
+
+    private static func ms(_ seconds: TimeInterval) -> String {
+        "\(Int((seconds * 1000).rounded()))ms"
+    }
+}