AWS SNS 取消订阅循环不释放内存 - 导致 Jetsam 终止应用程序

Question

问题

当我取消订阅我的端点订阅时，仪器内存图从 32MB 变为 300MB 并且应用程序被杀死 Jetsam。据我了解，AWS BFTasks 会自行清理……如果我删除 do...while 并允许它处理前 100 个订阅，一切正常。

进程

我的开发应用程序中有大约 8000 个订阅，这些应用程序使用 AWS SNS 将警报推送到 iOS 设备和电子邮件。在用户选择他们想要的订阅后，我删除他们现有的订阅，然后订阅新的订阅。 [_awsSnsClient listSubscriptions:request] returns 最多 100 个订阅，我遍历这些，根据需要执行 [_awsSnsClient unsubscribe:unsubscribeRequest]。然后获得下一个 100...

代码

- (void) awsUsubscribeAllSubscriptions {
    DLog(@"Removing existing subscriptions");

    AWSSNSListSubscriptionsInput *request = [AWSSNSListSubscriptionsInput new];

    __block Boolean sentLastUnsubscribe = NO; // YES when the last unsubscribe request was sent
    __block int pendingUnsubscribe = 0; // Number of outsianding unsubscribes (async process not yet complete)

    do {
        [[[_awsSnsClient listSubscriptions:request] continueWithSuccessBlock:^id(BFTask *task) {
            AWSSNSListSubscriptionsResponse *response = (AWSSNSListSubscriptionsResponse *)task.result;
            NSString *nextToken = response.nextToken;
            NSArray *subscriptions = response.subscriptions;
            for (AWSSNSSubscription *subscription in subscriptions) {
                if ([subscription.endpoint isEqualToString:_awsPlatformEndpoint.endpointArn]) {
                    AWSSNSUnsubscribeInput *unsubscribeRequest = [AWSSNSUnsubscribeInput new];
                    unsubscribeRequest.subscriptionArn = subscription.subscriptionArn;
                    pendingUnsubscribe++;
                    [[[_awsSnsClient unsubscribe:unsubscribeRequest] continueWithSuccessBlock:^id(BFTask *task) {
                        DLog(@"Unsubscribed from:%@",subscription.subscriptionArn);
                        return nil;
                    }] continueWithBlock:^id(BFTask *task) {
                        pendingUnsubscribe--;
                        if (task.error) {
                            // failed with error
                            ALog(@"Error unsubscribing to: %@, %@, %@", subscription, [task.error localizedDescription], [task.error localizedFailureReason]);
                        }
                        // If we have processed the last unsubscribe, then create topics and subscribe
                        if (sentLastUnsubscribe  && (pendingUnsubscribe <= 0)) {
                            [self awsCreateTopicsAndSubscriptions];
                        }
                        return nil;
                    }];
                }
            }
            request.nextToken = nextToken;
            if(!nextToken) sentLastUnsubscribe = YES; // Reached the end of the SNS subscriptions
            return nil;
        }] continueWithBlock:^id(BFTask *task) {
            if (task.error) {
                // failed with error
                ALog(@"Error listing subscriptions: %@, %@", [task.error localizedDescription], [task.error localizedFailureReason]);
            }
            return nil;
        }];
    } while (!sentLastUnsubscribe);
}

是否有更好的方法从端点删除所有 SNS 订阅？有没有办法在这个循环中强制释放任何保留的数据？

解决方案

同时使用递归和- waitUntilFinished。内存负载现在 低很多 。

-(void) awsUnsubscribeFromAllSubscriptionsWithNextToken:(NSString *)nextToken AndSubscribe:(BOOL)subscribe {
AWSSNSListSubscriptionsInput *request = [AWSSNSListSubscriptionsInput new];
request.nextToken = nextToken;
[[[_awsSnsClient listSubscriptions:request] continueWithSuccessBlock:^id(BFTask *task) {
    AWSSNSListSubscriptionsResponse *response = (AWSSNSListSubscriptionsResponse *)task.result;
    NSArray *subscriptions = response.subscriptions;
    for (AWSSNSSubscription *subscription in subscriptions) {
        if ([subscription.endpoint isEqualToString:_awsPlatformEndpoint.endpointArn]) {
            DLog(@"Unsubscribe from %@", subscription.topicArn);
            AWSSNSUnsubscribeInput *unsubscribeRequest = [AWSSNSUnsubscribeInput new];
            unsubscribeRequest.subscriptionArn = subscription.subscriptionArn;
            [[_awsSnsClient unsubscribe:unsubscribeRequest] waitUntilFinished];
        }
    }
    if(response.nextToken) {
        [self awsUnsubscribeFromAllSubscriptionsWithNextToken:response.nextToken AndSubscribe:subscribe];
    } else if (subscribe) {
        [self awsCreateTopicsAndSubscriptions];
    }
    return nil;
}] continueWithBlock:^id(BFTask *task) {
    if (task.error) {
        // failed with error
        ALog(@"Error listing subscriptions: %@, %@", [task.error localizedDescription], [task.error localizedFailureReason]);
    }
    return nil;
}];

}

Answer 1

请注意，- listSubscriptions: 是一个异步方法，returns 是立即执行的。您正在 for 循环中调用异步方法。这意味着您可能会在短时间内调用 - listSubscriptions: 数百次甚至数千次。

修复它最简单的方法是在异步块的末尾调用 - waitUntilFinished。它使整个方法同步

但是，一般情况下，您应该尽可能避免调用 - waitUntilFinished。 AWSKinesisRecorderTests.m有一个函数可以递归调用- getRecords:。您可以采用类似的模式。

AWS SNS 取消订阅循环不释放内存 - 导致 Jetsam 终止应用程序

AWS SNS Unsubscribe loop is not releasing memory - Causing Jetsam to kill app

amazon-web-services

amazon-sns

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