Create HTTP requests on a background queue.

Analytics/Classes/Internal/SEGHTTPClient.h

@@ -32,7 +32,7 @@ NS_ASSUME_NONNULL_BEGIN
  * NOTE: You need to re-dispatch within the completionHandler onto a desired queue to avoid threading issues.
  * Completion handlers are called on a dispatch queue internal to SEGHTTPClient. 
  */
-- (NSURLSessionUploadTask *)upload:(JSON_DICT)batch forWriteKey:(NSString *)writeKey completionHandler:(void (^)(BOOL retry))completionHandler;
+- (NSURLSessionUploadTask *)upload:(NSArray *)batch forWriteKey:(NSString *)writeKey completionHandler:(void (^)(BOOL retry))completionHandler;
 
 - (NSURLSessionDataTask *)settingsForWriteKey:(NSString *)writeKey completionHandler:(void (^)(BOOL success, JSON_DICT _Nullable settings))completionHandler;
 

Analytics/Classes/Internal/SEGHTTPClient.m

@@ -62,7 +62,7 @@ - (void)dealloc
 }
 
 
-- (NSURLSessionUploadTask *)upload:(NSDictionary *)batch forWriteKey:(NSString *)writeKey completionHandler:(void (^)(BOOL retry))completionHandler
+- (NSURLSessionUploadTask *)upload:(NSArray *)batch forWriteKey:(NSString *)writeKey completionHandler:(void (^)(BOOL retry))completionHandler
 {
     //    batch = SEGCoerceDictionary(batch);
     NSURLSession *session = [self sessionForWriteKey:writeKey];
@@ -75,11 +75,16 @@ - (NSURLSessionUploadTask *)upload:(NSDictionary *)batch forWriteKey:(NSString *
 
     [request setHTTPMethod:@"POST"];
 
+    // In particular, set the sentAt after the requestFactory is invoked so that it can be as up to date as possible.
+    NSMutableDictionary *payload = [[NSMutableDictionary alloc] init];
+    [payload setObject:iso8601FormattedString([NSDate date]) forKey:@"sentAt"];
+    [payload setObject:batch forKey:@"batch"];
+
     NSError *error = nil;
     NSException *exception = nil;
-    NSData *payload = nil;
+    NSData *payloadData = nil;
     @try {
-        payload = [NSJSONSerialization dataWithJSONObject:batch options:0 error:&error];
+        payloadData = [NSJSONSerialization dataWithJSONObject:batch options:0 error:&error];
     }
     @catch (NSException *exc) {
         exception = exc;
@@ -89,7 +94,7 @@ - (NSURLSessionUploadTask *)upload:(NSDictionary *)batch forWriteKey:(NSString *
         completionHandler(NO); // Don't retry this batch.
         return nil;
     }
-    NSData *gzippedPayload = [payload seg_gzippedData];
+    NSData *gzippedPayload = [payloadData seg_gzippedData];
 
     NSURLSessionUploadTask *task = [session uploadTaskWithRequest:request fromData:gzippedPayload completionHandler:^(NSData *_Nullable data, NSURLResponse *_Nullable response, NSError *_Nullable error) {
         if (error) {

Analytics/Classes/Internal/SEGSegmentIntegration.m

@@ -55,10 +55,12 @@ @interface SEGSegmentIntegration ()
 @property (nonatomic, strong) NSMutableArray *queue;
 @property (nonatomic, strong) NSDictionary *cachedStaticContext;
 @property (nonatomic, strong) NSURLSessionUploadTask *batchRequest;
+@property (nonatomic, assign) BOOL batchRequestInProgress; // Thread confined to serialQueue.
 @property (nonatomic, assign) UIBackgroundTaskIdentifier flushTaskID;
 @property (nonatomic, strong) SEGReachability *reachability;
 @property (nonatomic, strong) NSTimer *flushTimer;
 @property (nonatomic, strong) dispatch_queue_t serialQueue;
+@property (nonatomic, strong) dispatch_queue_t networkQueue;
 @property (nonatomic, strong) dispatch_queue_t backgroundTaskQueue;
 @property (nonatomic, strong) NSMutableDictionary *traits;
 @property (nonatomic, assign) SEGAnalytics *analytics;
@@ -87,8 +89,9 @@ - (id)initWithAnalytics:(SEGAnalytics *)analytics httpClient:(SEGHTTPClient *)ht
         self.reachability = [SEGReachability reachabilityWithHostname:@"google.com"];
         [self.reachability startNotifier];
         self.cachedStaticContext = [self staticContext];
-        self.serialQueue = seg_dispatch_queue_create_specific("io.segment.analytics.segmentio", DISPATCH_QUEUE_SERIAL);
-        self.backgroundTaskQueue = seg_dispatch_queue_create_specific("io.segment.analytics.backgroundTask", DISPATCH_QUEUE_SERIAL);
+        self.serialQueue = seg_dispatch_queue_create_specific("com.segment.analytics.segment", DISPATCH_QUEUE_SERIAL);
+        self.networkQueue = seg_dispatch_queue_create_specific("com.segment.analytics.segment.network", DISPATCH_QUEUE_SERIAL);
+        self.backgroundTaskQueue = seg_dispatch_queue_create_specific("com.segment.analytics.segment.backgroundTask", DISPATCH_QUEUE_SERIAL);
         self.flushTaskID = UIBackgroundTaskInvalid;
 
 #if !TARGET_OS_TV
@@ -487,7 +490,7 @@ - (void)flushWithMaxSize:(NSUInteger)maxBatchSize
             [self endBackgroundTask];
             return;
         }
-        if (self.batchRequest != nil) {
+        if (self.batchRequestInProgress) {
             SEGLog(@"%@ API request already in progress, not flushing again.", self);
             return;
         }
@@ -508,7 +511,7 @@ - (void)flushQueueByLength
     [self dispatchBackground:^{
         SEGLog(@"%@ Length is %lu.", self, (unsigned long)self.queue.count);
 
-        if (self.batchRequest == nil && [self.queue count] >= self.configuration.flushAt) {
+        if (!self.batchRequestInProgress && [self.queue count] >= self.configuration.flushAt) {
             [self flush];
         }
     }];
@@ -540,31 +543,37 @@ - (void)notifyForName:(NSString *)name userInfo:(id)userInfo
 
 - (void)sendData:(NSArray *)batch
 {
-    NSMutableDictionary *payload = [[NSMutableDictionary alloc] init];
-    [payload setObject:iso8601FormattedString([NSDate date]) forKey:@"sentAt"];
-    [payload setObject:batch forKey:@"batch"];
+    if (self.batchRequestInProgress) {
+        SEGLog(@"API request already in progress, not flushing again.");
+        return;
+    }
 
-    SEGLog(@"%@ Flushing %lu of %lu queued API calls.", self, (unsigned long)batch.count, (unsigned long)self.queue.count);
-    SEGLog(@"Flushing batch %@.", payload);
+    self.batchRequestInProgress = true;
 
-    self.batchRequest = [self.httpClient upload:payload forWriteKey:self.configuration.writeKey completionHandler:^(BOOL retry) {
-        [self dispatchBackground:^{
-            if (retry) {
-                [self notifyForName:SEGSegmentRequestDidFailNotification userInfo:batch];
+    seg_dispatch_specific_async(self.networkQueue, ^{
+        SEGLog(@"%@ Flushing %lu of %lu queued API calls.", self, (unsigned long)batch.count, (unsigned long)self.queue.count);
+
+        self.batchRequest = [self.httpClient upload:batch forWriteKey:self.configuration.writeKey completionHandler:^(BOOL retry) {
+            [self dispatchBackground:^{
+                self.batchRequestInProgress = false;
+
+                if (retry) {
+                    [self notifyForName:SEGSegmentRequestDidFailNotification userInfo:batch];
+                    self.batchRequest = nil;
+                    [self endBackgroundTask];
+                    return;
+                }
+
+                [self.queue removeObjectsInArray:batch];
+                [self persistQueue];
+                [self notifyForName:SEGSegmentRequestDidSucceedNotification userInfo:batch];
                 self.batchRequest = nil;
                 [self endBackgroundTask];
-                return;
-            }
-
-            [self.queue removeObjectsInArray:batch];
-            [self persistQueue];
-            [self notifyForName:SEGSegmentRequestDidSucceedNotification userInfo:batch];
-            self.batchRequest = nil;
-            [self endBackgroundTask];
+            }];
         }];
-    }];
 
-    [self notifyForName:SEGSegmentDidSendRequestNotification userInfo:batch];
+        [self notifyForName:SEGSegmentDidSendRequestNotification userInfo:batch];
+    });
 }
 
 - (void)applicationDidEnterBackground

AnalyticsTests/HTTPClientTest.swift

@@ -95,11 +95,8 @@ class HTTPClientTest: QuickSpec {
 
     describe("upload") {
       it("does not ask to retry for json error") {
-        let batch: [String: Any] = [
-          // Dates cannot be serialized as is so the json serialzation will fail.
-          "sentAt": NSDate(),
-          "batch": [["type": "track", "event": "foo"]],
-        ]
+        // Dates cannot be serialized as is so the json serialzation will fail.
+        let batch = [[ "foo" : NSDate() ] ]
         var done = false
         let task = client.upload(batch, forWriteKey: "bar") { retry in
           expect(retry) == false
@@ -109,7 +106,7 @@ class HTTPClientTest: QuickSpec {
         expect(done).toEventually(beTrue())
       }
 
-      let batch: [String: Any] = ["sentAt":"2016-07-19'T'19:25:06Z", "batch":[["type":"track", "event":"foo"]]]
+      let batch = [["type":"track", "event":"foo"]]
 
 
       it("does not ask to retry for 2xx response") {