ios - 从 Amazon S3 Bucket iOS 下载多个项目

Question

我最近在我的应用程序(耶，cocoapods!)中实现了新的 AWS 2.0 iOS SDK，并使用来自 Amazon 的示例代码设法正确配置访问和下载。我可以毫无问题地成功下载单个项目，但我需要能够下载基于当前 tableview 动态生成的多个文件。似乎没有办法设置批量下载，所以我只是想遍历一组对象并触发每个对象的下载。它有效，但如果列表包含多个项目，它就会开始随机失火。例如，如果我动态创建的列表中有 14 个项目，则将下载 12 个，甚至不会尝试下载其他 2 个。请求就消失了。在我的测试中，我添加了一个 sleep(1) 计时器，然后所有 14 个都被触发并下载，所以我猜我正在压倒下载请求，除非我放慢速度，否则它们会被丢弃。放慢速度并不理想……也许还有另一种方法？这是代码:

 - (IBAction)downloadAllPics:(UIBarButtonItem *)sender {
if (debug==1) {
    NSLog(@"Running %@ '%@'", self.class, NSStringFromSelector(_cmd));
}

CoreDataHelper *cdh =
[(AppDelegate *)[[UIApplication sharedApplication] delegate] cdh];

// for loop iterates through all of the items in the tableview
for (Item *item in self.frc.fetchedObjects) {

    NSString *docDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *downloadingFilePath1 = [NSString stringWithFormat:@"%@/%@@2x.jpg",docDir, item.imageName];
    NSURL *downloadingFileURL1 = [NSURL fileURLWithPath:downloadingFilePath1];

    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSError *error = nil;
    if ([fileManager fileExistsAtPath:downloadingFilePath1]) {
        fileAlreadyExists = TRUE;
        if (![fileManager removeItemAtPath:downloadingFilePath1
                                     error:&error]) {
            NSLog(@"Error: %@", error);
        }
    }
    __weak typeof(self) weakSelf = self;

    self.downloadRequest1 = [AWSS3TransferManagerDownloadRequest new];
    self.downloadRequest1.bucket = S3BucketName;
    //  self.downloadRequest1.key = S3KeyDownloadName1;
    self.downloadRequest1.key = [NSString stringWithFormat:@"images/%@@2x.jpg", item.imageName];
    self.downloadRequest1.downloadingFileURL = downloadingFileURL1;
    self.downloadRequest1.downloadProgress = ^(int64_t bytesWritten, int64_t totalBytesWritten, int64_t totalBytesExpectedToWrite){
        // update progress
        dispatch_sync(dispatch_get_main_queue(), ^{
            weakSelf.file1AlreadyDownloaded = totalBytesWritten;
            weakSelf.file1Size = totalBytesExpectedToWrite;
        });

    };

     // this launches the actual S3 transfer manager - it is successfully launched with each pass of loop
    [self downloadFiles];
}

[cdh backgroundSaveContext];

 }

启动 downloadFiles 方法:

 - (void) downloadFiles {
//if I add this sleep, all 14 download. If I don't usually 11-13 download.
sleep(1);
AWSS3TransferManager *transferManager = [AWSS3TransferManager defaultS3TransferManager];

__block int downloadCount = 0;

[[transferManager download:self.downloadRequest1] continueWithExecutor:[BFExecutor mainThreadExecutor] withBlock:^id(BFTask *task) {
     if (task.error != nil){
        if(task.error.code != AWSS3TransferManagerErrorCancelled && task.error.code != AWSS3TransferManagerErrorPaused){
            NSLog(@"%s Errorx: [%@]",__PRETTY_FUNCTION__, task.error);
        }
    } else {
        self.downloadRequest1 = nil;

    }
    return nil;
}];        
 }

一定有一种方法可以从 Amazon S3 存储桶中下载动态文件列表，对吗？也许有一个传输管理器允许一系列文件而不是单独处理它们？

感谢任何帮助。扎克

Answer 1

听起来像是请求超时间隔设置问题。

首先，当您配置 AWSServiceConfiguration *configuration = ... 时，尝试配置 timeoutIntervalForRequest 属性。此外，maxRetryCount 也是如此。 maxRetryCount 每次下载失败都会尝试下载。

AWSServiceConfiguration *configuration = [[AWSServiceConfiguration alloc] initWithRegion:DefaultServiceRegionType
                                                                     credentialsProvider:credentialsProvider];
[configuration setMaxRetryCount:2]; // 10 is the max
[configuration setTimeoutIntervalForRequest:120]; // 120 seconds

其次，对于多个项目的下载，尝试将每个 AWSTask 收集到一个数组中，并在组操作结束时获取结果。例如)

// task collector
NSMutableSet *uniqueTasks = [NSMutableSet new];

// Loop
for (0 -> numOfDownloads) {
     AWSS3TransferManagerDownloadRequest *downloadRequest = [AWSS3TransferManagerDownloadRequest new];
     [downloadRequest setBucket:S3BucketNameForProductImage];
     [downloadRequest setKey:filename];
     [downloadRequest setDownloadingFileURL:sourceURL];
     [showroomGroupDownloadRequests addObject:downloadRequest];

    AWSTask *task = [[AWSS3TransferManager defaultS3TransferManager] download:downloadRequest];
    [task continueWithBlock:^id(AWSTask *task) {
    // handle each individual operation
    if (task.error == nil) {

    }
    else if (task.error) {

    }
    // add to the tasks
    [uniqueTasks addObject:task];

    return nil;
}

[[AWSTask taskForCompletionOfAllTasks:tasks] continueWithBlock:^id(AWSTask *task) {
    if (task.error == nil) {
        // all downloads succeess
    }
    else if (task.error != nil) {
        // failure happen one of download
    }

   return nil;
}];