Efficient way to extract files and meta data from Amazon S3?

Question

Is there a more efficient way to list files from a bucket in Amazon S3 and also extract the meta data for each of those files? I'm using the AWS PHP SDK.

if ($paths = $s3->get_object_list('my-bucket')) {
    foreach($paths AS $path) {
        $meta = $s3->get_object_metadata('my-bucket', $path);
        echo $path . ' was modified on ' . $meta['LastModified'] . '<br />';
    }
}

At the moment I need to run get_object_list() to list all the files and then get_object_metadata() for each file to get its meta data.

If I have 100 files in my bucket, it makes 101 calls to get this data. It would be good if it's possible to do it in 1 call.

E.g:

if ($paths = $s3->get_object_list('my-bucket')) {
    foreach($paths AS $path) {
        echo $path['FileName'] . ' was modified on ' . $path['LastModified'] . '<br />';
    }
}

Answer 1

I know this is a bit old, but I encountered this problem and to solve it I extended the Aws sdk to use the batch functionality for this type of problem. It makes a lot quicker to retrieve custom meta data for lots of files. This is my code:

    /**
     * Name: Steves_Amazon_S3
     * 
     * Extends the AmazonS3 class in order to create a function to 
     * more efficiently retrieve a list of
     * files and their custom metadata using the CFBatchRequest function.
     * 
     * 
     */
    class Steves_Amazon_S3 extends AmazonS3 {

        public function get_object_metadata_batch($bucket, $filenames, $opt = null) {
            $batch = new CFBatchRequest();

            foreach ($filenames as $filename) {

                $this->batch($batch)->get_object_headers($bucket, $filename); // Get content-type
            }

            $response = $this->batch($batch)->send();

            // Fail if any requests were unsuccessful
            if (!$response->areOK()) {
                return false;
            }
            foreach ($response as $file) {
                $temp = array();
                $temp['name'] = (string) basename($file->header['_info']['url']);
                $temp['etag'] = (string) basename($file->header['etag']);
                $temp['size'] = $this->util->size_readable((integer) basename($file->header['content-length']));
                $temp['size_raw'] = basename($file->header['content-length']);
                $temp['last_modified'] = (string) date("jS M Y H:i:s", strtotime($file->header['last-modified']));
                $temp['last_modified_raw'] = strtotime($file->header['last-modified']);
                @$temp['creator_id'] = (string) $file->header['x-amz-meta-creator'];
                @$temp['client_view'] = (string) $file->header['x-amz-meta-client-view'];
                @$temp['user_view'] = (string) $file->header['x-amz-meta-user-view'];

                $result[] = $temp;
            }

            return $result;
        }
    }

Answer 2

You need to know that list_objects function has limit. It doesn't allows to load more than 1000 objects, even if max-keys option will be set to some large number.

To fix this you need to load data several times:

private function _getBucketObjects($prefix = '', $booOneLevelOny = false)
{
    $objects = array();
    $lastKey = null;
    do {
        $args = array();
        if (isset($lastKey)) {
            $args['marker'] = $lastKey;
        }

        if (strlen($prefix)) {
            $args['prefix'] = $prefix;
        }

        if($booOneLevelOny) {
            $args['delimiter'] = '/';
        }

        $res = $this->_client->list_objects($this->_bucket, $args);
        if (!$res->isOK()) {
            return null;
        }

        foreach ($res->body->Contents as $object) {
            $objects[] = $object;
            $lastKey = (string)$object->Key;
        }
        $isTruncated = (string)$res->body->IsTruncated;
        unset($res);
    } while ($isTruncated == 'true');

    return $objects;
}

As result - you'll have a full list of the objects.

---

What if you have some custom headers? They will be not returned via list_objects function. In this case this will help:

foreach (array_chunk($arrObjects, 1000) as $object_set) {
    $batch = new CFBatchRequest();
    foreach ($object_set as $object) {
        if(!$this->isFolder((string)$object->Key)) {
            $this->_client->batch($batch)->get_object_headers($this->_bucket, $this->preparePath((string)$object->Key));
        }
    }

    $response = $this->_client->batch($batch)->send();

    if ($response->areOK()) {
        foreach ($response as $arrHeaderInfo) {
            $arrHeaders[] = $arrHeaderInfo->header;
        }
    }
    unset($batch, $response);
}