[ios] Adds thread safe access to MGLNetworkConfiguration events dictionary (#15113)

4 files changed, 84 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
diff --git a/platform/ios/CHANGELOG.md b/platform/ios/CHANGELOG.md
index 9b7de7e73a..b187db42a3 100644
--- a/platform/ios/CHANGELOG.md
+++ b/platform/ios/CHANGELOG.md
@@ -42,6 +42,7 @@ Mapbox welcomes participation and contributions from everyone. Please read [CONT
 * Fixed an issue where the two-finger tilt gesture would continue after lifting one finger. ([#14969](https://github.com/mapbox/mapbox-gl-native/pull/14969))
 * Added `MGLMapView.compassView.visibility` and `MGLOrnamentVisibility` to allow configuration of compass visibility behavior. ([#15055](https://github.com/mapbox/mapbox-gl-native/pull/15055))
 * Fixed a bug where using the pinch gesture could result in an incorrect map center coordinate. ([#15097](https://github.com/mapbox/mapbox-gl-native/pull/15097))
+* Fixed a crash during network access. ([#15113](https://github.com/mapbox/mapbox-gl-native/pull/15113))
 
 ## 5.1.0 - June 19, 2019
 
diff --git a/platform/ios/ios.xcodeproj/project.pbxproj b/platform/ios/ios.xcodeproj/project.pbxproj
index 670e78a46c..98a651f13f 100644
--- a/platform/ios/ios.xcodeproj/project.pbxproj
+++ b/platform/ios/ios.xcodeproj/project.pbxproj
@@ -516,6 +516,7 @@
 		CA6914B520E67F50002DB0EE /* MGLAnnotationViewIntegrationTests.m in Sources */ = {isa = PBXBuildFile; fileRef = CA6914B420E67F50002DB0EE /* MGLAnnotationViewIntegrationTests.m */; };
 		CA7766832229C10E0008DE9E /* MGLCompactCalloutView.m in Sources */ = {isa = PBXBuildFile; fileRef = DA8848451CBAFB9800AB86E3 /* MGLCompactCalloutView.m */; };
 		CA7766842229C11A0008DE9E /* SMCalloutView.m in Sources */ = {isa = PBXBuildFile; fileRef = DA88488A1CBB037E00AB86E3 /* SMCalloutView.m */; };
+		CA86FF0E22D8D5A0009EB14A /* MGLNetworkConfigurationTests.m in Sources */ = {isa = PBXBuildFile; fileRef = CA86FF0D22D8D5A0009EB14A /* MGLNetworkConfigurationTests.m */; };
 		CA88DC3021C85D900059ED5A /* MGLStyleURLIntegrationTest.m in Sources */ = {isa = PBXBuildFile; fileRef = CA88DC2F21C85D900059ED5A /* MGLStyleURLIntegrationTest.m */; };
 		CA8FBC0921A47BB100D1203C /* MGLRendererConfigurationTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = CA8FBC0821A47BB100D1203C /* MGLRendererConfigurationTests.mm */; };
 		CAA69DA4206DCD0E007279CD /* Mapbox.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = DA4A26961CB6E795000B7809 /* Mapbox.framework */; };
@@ -1198,6 +1199,7 @@
 		CA5E5042209BDC5F001A8A81 /* MGLTestUtility.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; name = MGLTestUtility.h; path = ../../darwin/test/MGLTestUtility.h; sourceTree = "<group>"; };
 		CA65C4F721E9BB080068B0D4 /* MGLCluster.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = MGLCluster.h; sourceTree = "<group>"; };
 		CA6914B420E67F50002DB0EE /* MGLAnnotationViewIntegrationTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; name = MGLAnnotationViewIntegrationTests.m; path = "Annotation Tests/MGLAnnotationViewIntegrationTests.m"; sourceTree = "<group>"; };
+		CA86FF0D22D8D5A0009EB14A /* MGLNetworkConfigurationTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = MGLNetworkConfigurationTests.m; sourceTree = "<group>"; };
 		CA88DC2F21C85D900059ED5A /* MGLStyleURLIntegrationTest.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = MGLStyleURLIntegrationTest.m; sourceTree = "<group>"; };
 		CA8FBC0821A47BB100D1203C /* MGLRendererConfigurationTests.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; name = MGLRendererConfigurationTests.mm; path = ../../darwin/test/MGLRendererConfigurationTests.mm; sourceTree = "<group>"; };
 		CAD9D0A922A86D6F001B25EE /* MGLResourceTests.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; name = MGLResourceTests.mm; path = ../../darwin/test/MGLResourceTests.mm; sourceTree = "<group>"; };
@@ -2071,6 +2073,7 @@
 				357579811D502AD4000B822E /* Styling */,
 				409F43FB1E9E77D10048729D /* Swift Integration */,
 				4031ACFD1E9FD26900A3EA26 /* Test Helpers */,
+				CA86FF0D22D8D5A0009EB14A /* MGLNetworkConfigurationTests.m */,
 			);
 			name = "SDK Tests";
 			path = test;
@@ -3250,6 +3253,7 @@
 				DA2DBBCE1D51E80400D38FF9 /* MGLStyleLayerTests.m in Sources */,
 				DA35A2C61CCA9F8300E826B2 /* MGLCompassDirectionFormatterTests.m in Sources */,
 				DAE7DEC21E245455007505A6 /* MGLNSStringAdditionsTests.m in Sources */,
+				CA86FF0E22D8D5A0009EB14A /* MGLNetworkConfigurationTests.m in Sources */,
 				4085AF091D933DEA00F11B22 /* MGLTileSetTests.mm in Sources */,
 				DAEDC4341D603417000224FF /* MGLAttributionInfoTests.m in Sources */,
 				1F7454A91ED08AB400021D39 /* MGLLightTest.mm in Sources */,
diff --git a/platform/ios/test/MGLNetworkConfigurationTests.m b/platform/ios/test/MGLNetworkConfigurationTests.m
new file mode 100644
index 0000000000..bfb63f57af
--- /dev/null
+++ b/platform/ios/test/MGLNetworkConfigurationTests.m
@@ -0,0 +1,43 @@
+#import <Mapbox/Mapbox.h>
+#import <XCTest/XCTest.h>
+#import "MGLNetworkConfiguration_Private.h"
+
+@interface MGLNetworkConfigurationTests : XCTestCase
+@end
+
+@implementation MGLNetworkConfigurationTests
+
+// Regression test for https://github.com/mapbox/mapbox-gl-native/issues/14982
+- (void)testAccessingEventsFromMultipleThreads {
+    MGLNetworkConfiguration *configuration = [[MGLNetworkConfiguration alloc] init];
+    
+    // Concurrent
+    dispatch_queue_t queue = dispatch_queue_create("com.mapbox.testAccessingEventsFromMultipleThreads", DISPATCH_QUEUE_CONCURRENT);
+    
+    NSUInteger numberOfConcurrentBlocks = 20;
+    
+    XCTestExpectation *expectation = [self expectationWithDescription:@"wait-for-threads"];
+    expectation.expectedFulfillmentCount = numberOfConcurrentBlocks;
+    
+    for (NSUInteger i = 0; i < numberOfConcurrentBlocks; i++) {
+        
+        NSString *event = [NSString stringWithFormat:@"test://event-%ld", i];
+        NSString *resourceType = @"test";
+        
+        dispatch_async(queue, ^{
+            [configuration startDownloadEvent:event type:resourceType];
+            
+            NSURL *url = [NSURL URLWithString:event];
+            NSURLResponse *response = [[NSURLResponse alloc] initWithURL:url MIMEType:nil expectedContentLength:0 textEncodingName:nil];
+            
+            [configuration stopDownloadEventForResponse:response];
+            
+            dispatch_async(dispatch_get_main_queue(), ^{
+                [expectation fulfill];
+            });
+        });
+    }
+    
+    [self waitForExpectations:@[expectation] timeout:10.0];
+}
+@end