From 0acf84d21e260cf4b0f24322ab612a8c644a3e5d Mon Sep 17 00:00:00 2001
From: vahid torkaman <vahidt@spotify.com>
Date: Wed, 8 May 2024 15:15:02 +0200
Subject: [PATCH] use semaphore to make upload serialz

---
 Sources/Confidence/EventSenderEngine.swift    | 59 +++++++++++--------
 Sources/Confidence/EventStorage.swift         | 18 ------
 Tests/ConfidenceTests/EventUploaderMock.swift |  4 --
 3 files changed, 35 insertions(+), 46 deletions(-)

diff --git a/Sources/Confidence/EventSenderEngine.swift b/Sources/Confidence/EventSenderEngine.swift
index dd4cb245..46bfec33 100644
--- a/Sources/Confidence/EventSenderEngine.swift
+++ b/Sources/Confidence/EventSenderEngine.swift
@@ -22,7 +22,7 @@ final class EventSenderEngineImpl: EventSenderEngine {
     private let uploader: ConfidenceClient
     private let clientSecret: String
     private let payloadMerger: PayloadMerger = PayloadMergerImpl()
-    private let queue = DispatchQueue(label: "com.confidence.engine")
+    private let semaphore = DispatchSemaphore(value: 1)
 
     init(
         clientSecret: String,
@@ -53,38 +53,49 @@ final class EventSenderEngineImpl: EventSenderEngine {
         .store(in: &cancellables)
 
         uploadReqChannel.sink { [weak self] _ in
+            guard let self = self else { return }
+            await self.upload()
+        }
+        .store(in: &cancellables)
+    }
+
+    func upload() async {
+        await withSemaphore { [weak self] in
+            guard let self = self else { return }
             do {
-                guard let self = self else { return }
-                var batches: [[ConfidenceEvent]] = []
-                try queue.sync {
-                    try self.storage.startNewBatch()
-                    let ids = try storage.batchReadyIds()
-                    for id in ids {
-                        let events: [ConfidenceEvent] = try self.storage.eventsFrom(id: id)
-                        batches.append(events)
-                        do {
-                            try storage.remove(id: id)
-                        } catch {
+                try self.storage.startNewBatch()
+                let ids = try storage.batchReadyIds()
+                if ids.isEmpty {
+                    return
+                }
+                for id in ids {
+                    let events: [NetworkEvent] = try self.storage.eventsFrom(id: id)
+                        .compactMap { event in
+                            return NetworkEvent(
+                                eventDefinition: event.name,
+                                payload: NetworkStruct(fields: TypeMapper.convert(structure: event.payload).fields),
+                                eventTime: Date.backport.toISOString(date: event.eventTime))
                         }
+                    var shouldCleanup = false
+                    if events.isEmpty {
+                        shouldCleanup = true
+                    } else {
+                        shouldCleanup = try await self.uploader.upload(events: events)
                     }
-                }
 
-                for events in batches {
-                    let batch = events.compactMap { event in
-                        return NetworkEvent(
-                            eventDefinition: event.name,
-                            payload: NetworkStruct(fields: TypeMapper.convert(structure: event.payload).fields),
-                            eventTime: Date.backport.toISOString(date: event.eventTime))
-                    }
-                    let shouldCleanup = try await self.uploader.upload(events: batch)
-                    if !shouldCleanup {
-                        try storage.writeEvents(events: events)
+                    if shouldCleanup {
+                        try storage.remove(id: id)
                     }
                 }
             } catch {
             }
         }
-        .store(in: &cancellables)
+    }
+
+    func withSemaphore(callback: @escaping () async -> Void) async {
+        semaphore.wait()
+        await callback()
+        semaphore.signal()
     }
 
     func emit(eventName: String, message: ConfidenceStruct, context: ConfidenceStruct) {
diff --git a/Sources/Confidence/EventStorage.swift b/Sources/Confidence/EventStorage.swift
index 7fe5ed26..41d2825d 100644
--- a/Sources/Confidence/EventStorage.swift
+++ b/Sources/Confidence/EventStorage.swift
@@ -10,7 +10,6 @@ struct ConfidenceEvent: Codable {
 internal protocol EventStorage {
     func startNewBatch() throws
     func writeEvent(event: ConfidenceEvent) throws
-    func writeEvents(events: [ConfidenceEvent]) throws
     func batchReadyIds() throws -> [String]
     func eventsFrom(id: String) throws -> [ConfidenceEvent]
     func remove(id: String) throws
@@ -44,23 +43,6 @@ internal class EventStorageImpl: EventStorage {
         }
     }
 
-    func writeEvents(events: [ConfidenceEvent]) throws {
-        try storageQueue.sync {
-            guard let currentFileHandle = currentFileHandle else {
-                return
-            }
-            let encoder = JSONEncoder()
-            let serialied = try encoder.encode(events)
-            let delimiter = "\n".data(using: .utf8)
-            guard let delimiter else {
-                return
-            }
-            currentFileHandle.seekToEndOfFile()
-            try currentFileHandle.write(contentsOf: delimiter)
-            try currentFileHandle.write(contentsOf: serialied)
-        }
-    }
-
     func writeEvent(event: ConfidenceEvent) throws {
         try storageQueue.sync {
             guard let currentFileHandle = currentFileHandle else {
diff --git a/Tests/ConfidenceTests/EventUploaderMock.swift b/Tests/ConfidenceTests/EventUploaderMock.swift
index 24539a80..ffffeb46 100644
--- a/Tests/ConfidenceTests/EventUploaderMock.swift
+++ b/Tests/ConfidenceTests/EventUploaderMock.swift
@@ -27,10 +27,6 @@ final class EventStorageMock: EventStorage {
         events.removeAll()
     }
 
-    func writeEvents(events: [ConfidenceEvent]) throws {
-        self.events += events
-    }
-
     func writeEvent(event: ConfidenceEvent) throws {
         events.append(event)
     }