1 files changed, 36 insertions, 6 deletions

diff --git a/platform/darwin/src/MGLNetworkConfiguration.m b/platform/darwin/src/MGLNetworkConfiguration.m
index 40993c97b5..0e5046e7a3 100644
--- a/platform/darwin/src/MGLNetworkConfiguration.m
+++ b/platform/darwin/src/MGLNetworkConfiguration.m
@@ -11,6 +11,7 @@ NSString * const kMGLDownloadPerformanceEvent = @"mobile.performance_trace";
 @property (strong) NSURLSessionConfiguration *sessionConfig;
 @property (nonatomic, strong) NSMutableDictionary<NSString *, NSDictionary*> *events;
 @property (nonatomic, weak) id<MGLNetworkConfigurationMetricsDelegate> metricsDelegate;
+@property (nonatomic) dispatch_queue_t eventsQueue;
 
 @end
 
@@ -20,6 +21,7 @@ NSString * const kMGLDownloadPerformanceEvent = @"mobile.performance_trace";
     if (self = [super init]) {
         self.sessionConfiguration = nil;
         _events = [NSMutableDictionary dictionary];
+        _eventsQueue = dispatch_queue_create("com.mapbox.network-configuration", DISPATCH_QUEUE_CONCURRENT);
     }
     
     return self;
@@ -65,8 +67,9 @@ NSString * const kMGLDownloadPerformanceEvent = @"mobile.performance_trace";
 }
 
 - (void)startDownloadEvent:(NSString *)urlString type:(NSString *)resourceType {
-    if (urlString && ![self.events objectForKey:urlString]) {
-        [self.events setObject:@{ MGLStartTime: [NSDate date], MGLResourceType: resourceType } forKey:urlString];
+    if (urlString && ![self eventDictionaryForKey:urlString]) {
+        NSDate *startDate = [NSDate date];
+        [self setEventDictionary:@{ MGLStartTime: startDate, MGLResourceType: resourceType } forKey:urlString];
     }
 }
 
@@ -82,10 +85,13 @@ NSString * const kMGLDownloadPerformanceEvent = @"mobile.performance_trace";
 {
     if ([response isKindOfClass:[NSURLResponse class]]) {
         NSString *urlString = response.URL.relativePath;
-        if (urlString && [self.events objectForKey:urlString]) {
+        if (urlString && [self eventDictionaryForKey:urlString]) {
             NSDictionary *eventAttributes = [self eventAttributesForURL:response withAction:action];
-            [self.metricsDelegate networkConfiguration:self didGenerateMetricEvent:eventAttributes];
-            [self.events removeObjectForKey:urlString];
+            [self removeEventDictionaryForKey:urlString];
+
+            dispatch_async(dispatch_get_main_queue(), ^{
+                [self.metricsDelegate networkConfiguration:self didGenerateMetricEvent:eventAttributes];
+            });            
         }
     }
     
@@ -94,7 +100,7 @@ NSString * const kMGLDownloadPerformanceEvent = @"mobile.performance_trace";
 - (NSDictionary *)eventAttributesForURL:(NSURLResponse *)response withAction:(NSString *)action
 {
     NSString *urlString = response.URL.relativePath;
-    NSDictionary *parameters = [self.events objectForKey:urlString];
+    NSDictionary *parameters = [self eventDictionaryForKey:urlString];
     NSDate *startDate = [parameters objectForKey:MGLStartTime];
     NSDate *endDate = [NSDate date];
     NSTimeInterval elapsedTime = [endDate timeIntervalSinceDate:startDate];
@@ -129,4 +135,28 @@ NSString * const kMGLDownloadPerformanceEvent = @"mobile.performance_trace";
              };
 }
 
+#pragma mark - Events dictionary access
+
+- (nullable NSDictionary*)eventDictionaryForKey:(nonnull NSString*)key {
+    __block NSDictionary *dictionary;
+    
+    dispatch_sync(self.eventsQueue, ^{
+        dictionary = [self.events objectForKey:key];
+    });
+    
+    return dictionary;
+}
+
+- (void)setEventDictionary:(nonnull NSDictionary*)dictionary forKey:(nonnull NSString*)key {
+    dispatch_barrier_async(self.eventsQueue, ^{
+        [self.events setObject:dictionary forKey:key];
+    });
+}
+
+- (void)removeEventDictionaryForKey:(nonnull NSString*)key {
+    dispatch_barrier_async(self.eventsQueue, ^{
+        [self.events removeObjectForKey:key];
+    });
+}
+
 @end