Retry requests with a backoff strategy & keep max retries

* Keep max retries for now so we don't spam the server with requests when it is in trouble to avoid retrying forever.
* Let a request retry 4 times (so total 5 times) with backoff strategy calculated with multiples of 3.
* Remove some no longer used tag delay variables from common defines

Author: nan-li

iOS_SDK/OneSignalSDK/OneSignalCore/Source/API/OneSignalClient.m

@@ -59,8 +59,8 @@ -(instancetype)init {
 
 - (NSURLSessionConfiguration *)configurationWithCachingPolicy:(NSURLRequestCachePolicy)policy {
     NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
-    configuration.timeoutIntervalForRequest = REQUEST_TIMEOUT_REQUEST;
-    configuration.timeoutIntervalForResource = REQUEST_TIMEOUT_RESOURCE;
+    configuration.timeoutIntervalForRequest = REQUEST_TIMEOUT_REQUEST; // TODO: Are these anything?
+    configuration.timeoutIntervalForResource = REQUEST_TIMEOUT_RESOURCE; // TODO: Are these anything?
 
     //prevent caching of requests, this mainly impacts OSRequestGetIosParams,
     //since the OSRequestGetTags endpoint has a caching header policy
@@ -333,10 +333,11 @@ - (BOOL)willReattemptRequest:(int)statusCode withRequest:(OneSignalRequest *)req
         OSReattemptRequest *reattempt = [OSReattemptRequest withRequest:request successBlock:successBlock failureBlock:failureBlock];
 
         if (async) {
-            //retry again in 15 seconds
-            [OneSignalLog onesignalLog:ONE_S_LL_DEBUG message:[NSString stringWithFormat:@"Re-scheduling request (%@) to be re-attempted in %.3f seconds due to failed HTTP request with status code %i", NSStringFromClass([request class]), REATTEMPT_DELAY, (int)statusCode]];
+            //retry again in an increasing interval calculated with reattemptDelay
+            double reattemptDelay = [self calculateReattemptDelay:request.reattemptCount];
+            [OneSignalLog onesignalLog:ONE_S_LL_DEBUG message:[NSString stringWithFormat:@"Re-scheduling request (%@) to be re-attempted in %.3f seconds due to failed HTTP request with status code %i", NSStringFromClass([request class]), reattemptDelay, (int)statusCode]];
             [OneSignalCoreHelper dispatch_async_on_main_queue:^{
-                [self performSelector:@selector(reattemptRequest:) withObject:reattempt afterDelay:REATTEMPT_DELAY];
+                [self performSelector:@selector(reattemptRequest:) withObject:reattempt afterDelay:reattemptDelay];
             }];
         } else {
             //retry again immediately
@@ -349,6 +350,11 @@ - (BOOL)willReattemptRequest:(int)statusCode withRequest:(OneSignalRequest *)req
     return false;
 }
 
+// A request will retry with intervals of 5, 15 , 45, 135 seconds...
+- (double)calculateReattemptDelay:(int)reattemptCount {
+    return REATTEMPT_DELAY * pow(3, reattemptCount);
+}
+
 - (void)prettyPrintDebugStatementWithRequest:(OneSignalRequest *)request {
     if (![NSJSONSerialization isValidJSONObject:request.parameters])
         return;

iOS_SDK/OneSignalSDK/OneSignalCore/Source/OneSignalCommonDefines.h

@@ -231,13 +231,10 @@ typedef enum {GET, POST, HEAD, PUT, DELETE, OPTIONS, CONNECT, TRACE, PATCH} HTTP
 
 #ifndef OS_TEST
     // OneSignal API Client Defines
-    #define REATTEMPT_DELAY 30.0
+    #define REATTEMPT_DELAY 5.0
     #define REQUEST_TIMEOUT_REQUEST 120.0 //for most HTTP requests
     #define REQUEST_TIMEOUT_RESOURCE 120.0 //for loading a resource like an image
-    #define MAX_ATTEMPT_COUNT 3
-
-    // Send tags batch delay
-    #define SEND_TAGS_DELAY 5.0
+    #define MAX_ATTEMPT_COUNT 5
 
     // the max number of UNNotificationCategory ID's the SDK will register
     #define MAX_CATEGORIES_SIZE 128
@@ -254,9 +251,6 @@ typedef enum {GET, POST, HEAD, PUT, DELETE, OPTIONS, CONNECT, TRACE, PATCH} HTTP
     #define REQUEST_TIMEOUT_RESOURCE 0.02 //for loading a resource like an image
     #define MAX_ATTEMPT_COUNT 3
 
-    // Send tags batch delay
-    #define SEND_TAGS_DELAY 0.005
-
     // the max number of UNNotificationCategory ID's the SDK will register
     #define MAX_CATEGORIES_SIZE 5