Merge pull request #390 from Countly/back_off_mech

feat: back of mech

Author: turtledreams

CHANGELOG.md

@@ -2,6 +2,8 @@
 * Adding SDK health check requests after init
 * The feedback widgets now have fullscreen and transparent backgrounds for a cleaner look.
 * Added a config method to disable server config in the initialization "disableSDKBehaviorSettingsUpdates()".
+* Improved request queue handling, added a backoff mechanism to the SDK to better handle cases where the server responds slowly, enabled by default.
+* Added a config method to disable backoff mechanism "disableBackoffMechanism"
 
 ## 25.4.1
 * Mitigated an issue that could occur while serializing events to improve stability, performance and memory usage.

CountlyConfig.h

@@ -680,6 +680,11 @@ typedef enum : NSUInteger
  */
 @property(nonatomic) BOOL disableSDKBehaviorSettingsUpdates;
 
+/**
+ * Will disable back off mechanism
+ */
+@property (nonatomic) BOOL disableBackoffMechanism;
+
 #if (TARGET_OS_IOS)
 /**
  * Variable to access content configurations.

CountlyConnectionManager.m

@@ -5,6 +5,7 @@
 // Please visit www.count.ly for more information.
 
 #import "CountlyCommon.h"
+#import <stdatomic.h>
 
 @interface CountlyConnectionManager ()
 {
@@ -16,6 +17,8 @@ @interface CountlyConnectionManager ()
 @property (nonatomic) NSURLSession* URLSession;
 
 @property (nonatomic, strong) NSDate *startTime;
+@property (nonatomic, assign) atomic_bool backoff;
+
 
 @end
 
@@ -82,6 +85,7 @@ @interface CountlyConnectionManager ()
 NSString* const kCountlyEndpointSurveys = @"/surveys";
 
 const NSInteger kCountlyGETRequestMaxLength = 2048;
+static const NSTimeInterval CONNECTION_TIMEOUT = 30.0;
 
 @implementation CountlyConnectionManager : NSObject
 
@@ -101,6 +105,7 @@ - (instancetype)init
     {
         unsentSessionLength = 0.0;
         isSessionStarted = NO;
+        atomic_init(&_backoff, NO);
     }
 
     return self;
@@ -176,6 +181,12 @@ - (void)proceedOnQueue
         return;
     }
 
+    BOOL backoffFlag = atomic_load(&_backoff) ? YES : NO;
+    if (backoffFlag) {
+        CLY_LOG_I(@"%s, currently backed off, skipping proceeding the queue", __FUNCTION__);
+        return;
+    }
+    
     if (!self.startTime) {
         self.startTime = [NSDate date]; // Record start time only when it's not already recorded
         CLY_LOG_D(@"Proceeding on queue started, queued request count %lu", [CountlyPersistency.sharedInstance remainingRequestCount]);
@@ -212,6 +223,8 @@ - (void)proceedOnQueue
         return;
     }
 
+    _URLSessionConfiguration.timeoutIntervalForRequest = CONNECTION_TIMEOUT;
+    _URLSessionConfiguration.timeoutIntervalForResource = CONNECTION_TIMEOUT;
     NSString* queryString = firstItemInQueue;
     NSString* endPoint = kCountlyEndpointI;
 
@@ -271,11 +284,12 @@ - (void)proceedOnQueue
     }
 
     request.cachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
-
+    NSDate *startTimeRequest = [NSDate date];
     self.connection = [self.URLSession dataTaskWithRequest:request completionHandler:^(NSData * data, NSURLResponse * response, NSError * error)
     {
         self.connection = nil;
-
+        NSDate *endTimeRequest = [NSDate date];
+        long duration = (long)[endTimeRequest timeIntervalSinceDate:startTimeRequest];
 
         CLY_LOG_V(@"Approximate received data size for request <%p> is %ld bytes.", (id)request, (long)data.length);
 
@@ -294,8 +308,15 @@ - (void)proceedOnQueue
                 [CountlyPersistency.sharedInstance removeFromQueue:firstItemInQueue];
 
                 [CountlyPersistency.sharedInstance saveToFile];
-
-                [self proceedOnQueue];
+                
+                if(CountlyServerConfig.sharedInstance.backoffMechanism && [self backoff:duration queryString:queryString]){
+                    CLY_LOG_D(@"%s, backed off dropping proceeding the queue", __FUNCTION__);
+                    self.startTime = nil;
+                    [self backoffCountdown];
+                } else {
+                    [self proceedOnQueue];
+
+                }
             }
             else
             {
@@ -320,6 +341,54 @@ - (void)proceedOnQueue
     [self logRequest:request];
 }
 
+- (BOOL)backoff:(long)responseTimeSeconds queryString:(NSString *)queryString
+{
+    BOOL result = NO;
+    // Check if the current response time is within acceptable limits
+    if (responseTimeSeconds >= [CountlyServerConfig.sharedInstance bomAcceptedTimeoutSeconds]) {
+        // Check if the remaining request count is within acceptable limits
+        NSUInteger remainingRequests = [CountlyPersistency.sharedInstance remainingRequestCount];
+        NSUInteger threshold = (NSUInteger)(CountlyPersistency.sharedInstance.storedRequestsLimit * [CountlyServerConfig.sharedInstance bomRQPercentage]);
+        
+        if (remainingRequests <= threshold) {
+            // Calculate the age of the current request
+            double requestTimestamp = [[queryString cly_valueForQueryStringKey:kCountlyQSKeyTimestamp] longLongValue] / 1000.0;
+            double requestAgeInSeconds = [NSDate date].timeIntervalSince1970 - requestTimestamp;
+            
+            if (requestAgeInSeconds <= [CountlyServerConfig.sharedInstance bomRequestAge] * 3600.0) {
+                // Server is too busy, back off
+                result = YES;
+                [CountlyHealthTracker.sharedInstance logBackoffRequest];
+            }
+        }
+    }
+    
+    if (!result) {
+        [CountlyHealthTracker.sharedInstance logConsecutiveBackoffRequest];
+    }
+    
+    return result;
+}
+
+- (void)backoffCountdown
+{
+    __weak typeof(self) weakSelf = self;
+    CLY_LOG_D(@"%s, backed off, countdown start for %f seconds", __FUNCTION__, [CountlyServerConfig.sharedInstance bomDuration]);
+
+    atomic_store(&_backoff, YES);
+    dispatch_time_t delay = dispatch_time(DISPATCH_TIME_NOW, (int64_t)([CountlyServerConfig.sharedInstance bomDuration] * NSEC_PER_SEC));
+    dispatch_after(delay, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+        __strong typeof(weakSelf) strongSelf = weakSelf;
+        if (!strongSelf) return;
+        
+        
+        CLY_LOG_D(@"%s, countdown finished, running tick in background thread", __FUNCTION__);
+        atomic_store(&strongSelf->_backoff, NO);
+        [strongSelf proceedOnQueue];
+    });
+}
+
+
 - (NSString*)extractAndRemoveOverrideEndPoint:(NSString **)queryString
 {
     if([*queryString containsString:kCountlyNewEndPoint]) {

CountlyHealthTracker.h

@@ -20,6 +20,8 @@
 
 - (void)logBackoffRequest;
 
+- (void)logConsecutiveBackoffRequest;
+
 - (void)clearAndSave;
 
 - (void)saveState;

CountlyHealthTracker.m

@@ -15,6 +15,8 @@ @interface CountlyHealthTracker ()
 @property (nonatomic, assign) long countLogWarning;
 @property (nonatomic, assign) long countLogError;
 @property (nonatomic, assign) long countBackoffRequest;
+@property (nonatomic, assign) long countConsecutiveBackoffRequest;
+@property (nonatomic, assign) long consecutiveBackoffRequest;
 @property (nonatomic, assign) NSInteger statusCode;
 @property (nonatomic, strong) NSString *errorMessage;
 @property (nonatomic, assign) BOOL healthCheckEnabled;
@@ -29,12 +31,14 @@ @implementation CountlyHealthTracker
 NSString * const keyStatusCode = @"RStatC";
 NSString * const keyErrorMessage = @"REMsg";
 NSString * const keyBackoffRequest = @"BReq";
+NSString * const keyConsecutiveBackoffRequest = @"CBReq";
 
 NSString * const requestKeyErrorCount = @"el";
 NSString * const requestKeyWarningCount = @"wl";
 NSString * const requestKeyStatusCode = @"sc";
 NSString * const requestKeyRequestError = @"em";
-NSString * const requestKeyBackoffRequest = @"br";
+NSString * const requestKeyBackoffRequest = @"bom";
+NSString * const requestKeyConsecutiveBackoffRequest = @"cbom";
 
 + (instancetype)sharedInstance {
     static CountlyHealthTracker *instance = nil;
@@ -69,6 +73,7 @@ - (void)setupInitialCounters:(NSDictionary *)initialState {
     self.statusCode = [initialState[keyStatusCode] integerValue];
     self.errorMessage = initialState[keyErrorMessage] ?: @"";
     self.countBackoffRequest = [initialState[keyBackoffRequest] longValue];
+    self.consecutiveBackoffRequest = [initialState[keyConsecutiveBackoffRequest] longValue];
 
     CLY_LOG_D(@"%s, Loaded initial health check state: [%@]", __FUNCTION__, initialState);
 }
@@ -97,6 +102,12 @@ - (void)logFailedNetworkRequestWithStatusCode:(NSInteger)statusCode
 
 - (void)logBackoffRequest {
     self.countBackoffRequest++;
+    self.countConsecutiveBackoffRequest++;
+}
+
+- (void)logConsecutiveBackoffRequest {
+    self.consecutiveBackoffRequest = MAX(self.consecutiveBackoffRequest, self.countConsecutiveBackoffRequest);
+    self.countConsecutiveBackoffRequest = 0;
 }
 
 - (void)clearAndSave {
@@ -105,12 +116,15 @@ - (void)clearAndSave {
 }
 
 - (void)saveState {
+    [self logConsecutiveBackoffRequest];
+    
     NSDictionary *healthCheckState = @{
         keyLogWarning: @(self.countLogWarning),
         keyLogError: @(self.countLogError),
         keyStatusCode: @(self.statusCode),
         keyErrorMessage: self.errorMessage ?: @"",
-        keyBackoffRequest: @(self.countBackoffRequest)
+        keyBackoffRequest: @(self.countBackoffRequest),
+        keyConsecutiveBackoffRequest: @(self.consecutiveBackoffRequest)
     };
 
     [CountlyPersistency.sharedInstance storeHealthCheckTrackerState:healthCheckState];
@@ -124,6 +138,8 @@ - (void)clearValues {
     self.statusCode = -1;
     self.errorMessage = @"";
     self.countBackoffRequest = 0;
+    self.consecutiveBackoffRequest = 0;
+    self.countConsecutiveBackoffRequest = 0;
 }
 
 - (void)sendHealthCheck {
@@ -186,7 +202,8 @@ - (NSURLRequest *)healthCheckRequest {
         requestKeyWarningCount: @(self.countLogWarning),
         requestKeyStatusCode: @(self.statusCode),
         requestKeyRequestError: self.errorMessage ?: @"",
-        requestKeyBackoffRequest: @(self.countBackoffRequest)
+        requestKeyBackoffRequest: @(self.countBackoffRequest),
+        requestKeyConsecutiveBackoffRequest: @(self.consecutiveBackoffRequest)
     }]];
 
     queryString = [queryString stringByAppendingFormat:@"&%@=%@", @"metrics", [self dictionaryToJsonString:@{

CountlyServerConfig.h

@@ -39,5 +39,10 @@ extern NSString* const kCountlySCKeySC;
 - (BOOL)sessionTrackingEnabled;
 - (BOOL)locationTrackingEnabled;
 - (BOOL)refreshContentZoneEnabled;
+- (BOOL)backoffMechanism;
+- (NSInteger)bomAcceptedTimeoutSeconds;
+- (double)bomRQPercentage;
+- (NSInteger)bomRequestAge;
+- (NSInteger)bomDuration;
 @end