/**
* Gets an object stored in S3 and downloads it into the specified file. This method includes the
* one-time retry mechanism after integrity check failure on the downloaded file. It will also
* return immediately after getting null valued S3Object (when getObject request does not meet the
* specified constraints).
*
* @param file The file to store the object's data in.
* @param safeS3DownloadTask The implementation of SafeS3DownloadTask interface which allows user
* to get access to all the visible variables at the calling site of this method.
*/
public static S3Object retryableDownloadS3ObjectToFile(
File file, RetryableS3DownloadTask retryableS3DownloadTask) {
boolean hasRetried = false;
boolean needRetry;
S3Object s3Object;
do {
needRetry = false;
s3Object = retryableS3DownloadTask.getS3ObjectStream();
if (s3Object == null) return null;
try {
ServiceUtils.downloadObjectToFile(
s3Object, file, retryableS3DownloadTask.needIntegrityCheck());
} catch (AmazonClientException ace) {
// Determine whether an immediate retry is needed according to the captured
// AmazonClientException.
// (There are three cases when downloadObjectToFile() throws AmazonClientException:
// 1) SocketException or SSLProtocolException when writing to disk (e.g. when user aborts
// the download)
// 2) Other IOException when writing to disk
// 3) MD5 hashes don't match
// The current code will retry the download only when case 2) or 3) happens.
if (ace.getCause() instanceof SocketException
|| ace.getCause() instanceof SSLProtocolException) {
throw ace;
} else {
needRetry = true;
if (hasRetried) throw ace;
else {
log.info(
"Retry the download of object "
+ s3Object.getKey()
+ " (bucket "
+ s3Object.getBucketName()
+ ")",
ace);
hasRetried = true;
}
}
} finally {
try {
s3Object.getObjectContent().abort();
} catch (IOException e) {
}
}
} while (needRetry);
return s3Object;
}
