Merge pull request #50 from outfoxx/fix/event_source_backoff

Rework reconnect backoff to retry immediately and backoff quicker
outfoxx · Oct 23, 2023 · 6663ca5 · 6663ca5
2 parents 11c4eb7 + aeb5538
commit 6663ca5
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Showing 2 changed files with 19 additions and 12 deletions.
diff --git a/Sources/Sunday/EventSource.swift b/Sources/Sunday/EventSource.swift
@@ -71,7 +71,7 @@ public class EventSource {
   ///
   /// - SeeAlso: `EventSource.retryTime`
   ///
-  public static var retryTimeDefault = DispatchTimeInterval.milliseconds(500)
+  public static var retryTimeDefault = DispatchTimeInterval.milliseconds(100)
 
   /// Global default time interval for event timeout.
   ///
@@ -94,10 +94,11 @@ public class EventSource {
   /// alter the global default. Each `EventSource` can override
   ///  this setting in its initializer.
   ///
-  public static var eventTimeoutCheckIntervalDefault = DispatchTimeInterval.seconds(2)
+  public static var eventTimeoutCheckIntervalDefault = DispatchTimeInterval.seconds(100)
 
   // Maximum multiplier for the backoff algorithm
-  private static let maxRetryTimeMultiplier = 30
+  private static let maxRetryTimeMultiplier = 12
+  private static let retryExponent = 2.6
 
 
   /// Current state of the `EventSource`.
@@ -572,21 +573,17 @@ public class EventSource {
     reconnectTimeoutTask = nil
   }
 
-  private static func calculateRetryDelay(
+  static func calculateRetryDelay(
     retryAttempt: Int,
     retryTime: DispatchTimeInterval,
     lastConnectTime: DispatchTimeInterval
   ) -> DispatchTimeInterval {
 
-    let retryAttempt = Double(retryAttempt)
+    let retryMultiplier = Double(min(retryAttempt, Self.maxRetryTimeMultiplier))
     let retryTime = Double(retryTime.totalMilliseconds)
 
     // calculate total delay
-    let backOffDelay = pow(retryAttempt, 2.0) * retryTime
-    var retryDelay = min(
-      retryTime + backOffDelay,
-      retryTime * Double(Self.maxRetryTimeMultiplier)
-    )
+    var retryDelay = pow(retryMultiplier, retryExponent) * retryTime
 
     // Adjust delay by amount of time last connect
     // cycle took, except on the first attempt

diff --git a/Tests/SundayTests/EventSourceTests.swift b/Tests/SundayTests/EventSourceTests.swift
@@ -15,7 +15,7 @@
  */
 
 import Foundation
-import Sunday
+@testable import Sunday
 import SundayServer
 import XCTest
 
@@ -344,7 +344,7 @@ class EventSourceTests: XCTestCase {
 
     waitForExpectations()
 
-    XCTAssertEqual(eventSource.retryTime, .milliseconds(500))
+    XCTAssertEqual(eventSource.retryTime, .milliseconds(100))
   }
 
   func testReconnectsWithLastEventId() throws {
@@ -606,4 +606,14 @@ class EventSourceTests: XCTestCase {
     waitForExpectations()
   }
 
+  func testPrintRetryDelay() {
+
+    for attempt in 0 ..< 100 {
+      print(EventSource.calculateRetryDelay(retryAttempt: attempt,
+                                            retryTime: EventSource.retryTimeDefault,
+                                            lastConnectTime: .milliseconds(100)))
+    }
+
+  }
+
 }