S3 API

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Alluxio supports a RESTful API that is compatible with the basic operations of the Amazon S3 API.

The Alluxio S3 API should be used by applications designed to communicate with an S3-like storage and would benefit from the other features provided by Alluxio, such as data caching, data sharing with file system based applications, and storage system abstraction (e.g., using Ceph instead of S3 as the backing store). For example, a simple application that downloads reports generated by analytic tasks can use the S3 API instead of the more complex file system API.

There are performance implications of using the S3 API. The S3 API leverages the Alluxio proxy, introducing an extra hop. For optimal performance, it is recommended to run the proxy server and an Alluxio worker on each compute node. It is also recommended to put all the proxy servers behind a load balancer.

Features support

The following table describes the support status for current Amazon S3 functional features:

S3 FeatureStatus
List Buckets Supported
Delete Buckets Supported
Create Bucket Supported
Bucket Lifecycle Not Supported
Policy (Buckets, Objects) Not Supported
Bucket ACLs (Get, Put) Not Supported
Bucket Location Not Supported
Bucket Notification Not Supported
Bucket Object Versions Not Supported
Get Bucket Info (HEAD) Not Supported
Put Object Supported
Delete Object Supported
Get Object Supported
Get Object Info (HEAD) Supported
Get Object (Range Query) Not Supported [ALLUXIO-3321]
Object ACLs (Get, Put) Not Supported
POST Object Not Supported
Copy Object Not Supported
Multipart Uploads Supported

Language support

Alluxio S3 client supports various programming languages, such as C++, Java, Python, Golang, and Ruby. In this documentation, we use curl REST calls and python S3 client as usage examples.

Example Usage

REST API

For example, you can run the following RESTful API calls to an Alluxio cluster running on localhost. The Alluxio proxy is listening at port 39999 by default.

Create a bucket

# curl -i -X PUT http://localhost:39999/api/v1/s3/testbucket

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:23:18 GMT
Content-Length: 0
Server: Jetty(9.2.z-SNAPSHOT)

Get the bucket (listing objects)

# curl -i -X GET http://localhost:39999/api/v1/s3/testbucket

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:23:56 GMT
Content-Type: application/xml
Content-Length: 191
Server: Jetty(9.2.z-SNAPSHOT)

<ListBucketResult><Name>/testbucket</Name><Prefix/><ContinuationToken/><NextContinuationToken/><KeyCount>0</KeyCount><MaxKeys>1000</MaxKeys><IsTruncated>false</IsTruncated></ListBucketResult>

Put an object

Assuming there is an existing file on local file system called LICENSE:

# curl -i -X PUT -T "LICENSE" http://localhost:39999/api/v1/s3/testbucket/testobject

HTTP/1.1 100 Continue

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:24:32 GMT
ETag: "911df44b7ff57801ca8d74568e4ebfbe"
Content-Length: 0
Server: Jetty(9.2.z-SNAPSHOT)

Get the object:

# curl -i -X GET http://localhost:39999/api/v1/s3/testbucket/testobject

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:24:57 GMT
Last-Modified: Tue, 18 Jun 2019 21:24:33 GMT
Content-Type: application/xml
Content-Length: 27040
Server: Jetty(9.2.z-SNAPSHOT)

.................. Content of the test file ...................

Listing a bucket with one object

# curl -i -X GET http://localhost:39999/api/v1/s3/testbucket

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:25:27 GMT
Content-Type: application/xml
Content-Length: 354
Server: Jetty(9.2.z-SNAPSHOT)

<ListBucketResult><Name>/testbucket</Name><Prefix/><ContinuationToken/><NextContinuationToken/><KeyCount>1</KeyCount><MaxKeys>1000</MaxKeys><IsTruncated>false</IsTruncated><Contents><Key>testobject</Key><LastModified>2019-06-18T14:24:33.029Z</LastModified><ETag></ETag><Size>27040</Size><StorageClass>STANDARD</StorageClass></Contents></ListBucketResult>

Listing a bucket with multiple objects

You can upload more files and use the max-keys and continuation-token as the GET bucket request parameter. For example:

# curl -i -X PUT -T "LICENSE" http://localhost:39999/api/v1/s3/testbucket/key1

HTTP/1.1 100 Continue

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:26:05 GMT
ETag: "911df44b7ff57801ca8d74568e4ebfbe"
Content-Length: 0
Server: Jetty(9.2.z-SNAPSHOT)

# curl -i -X PUT -T "LICENSE" http://localhost:39999/api/v1/s3/testbucket/key2

HTTP/1.1 100 Continue

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:26:28 GMT
ETag: "911df44b7ff57801ca8d74568e4ebfbe"
Content-Length: 0
Server: Jetty(9.2.z-SNAPSHOT)

# curl -i -X PUT -T "LICENSE" http://localhost:39999/api/v1/s3/testbucket/key3

HTTP/1.1 100 Continue

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:26:43 GMT
ETag: "911df44b7ff57801ca8d74568e4ebfbe"
Content-Length: 0
Server: Jetty(9.2.z-SNAPSHOT)

# curl -i -X GET http://localhost:39999/api/v1/s3/testbucket\?max-keys\=2

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:26:57 GMT
Content-Type: application/xml
Content-Length: 528
Server: Jetty(9.2.z-SNAPSHOT)

<ListBucketResult><Name>/testbucket</Name><Prefix/><ContinuationToken/><NextContinuationToken>key3</NextContinuationToken><KeyCount>2</KeyCount><MaxKeys>2</MaxKeys><IsTruncated>true</IsTruncated><Contents><Key>key1</Key><LastModified>2019-06-18T14:26:05.694Z</LastModified><ETag></ETag><Size>27040</Size><StorageClass>STANDARD</StorageClass></Contents><Contents><Key>key2</Key><LastModified>2019-06-18T14:26:28.153Z</LastModified><ETag></ETag><Size>27040</Size><StorageClass>STANDARD</StorageClass></Contents></ListBucketResult>

# curl -i -X GET http://localhost:39999/api/v1/s3/testbucket\?max-keys\=2\&continuation-token\=key3

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:28:14 GMT
Content-Type: application/xml
Content-Length: 531
Server: Jetty(9.2.z-SNAPSHOT)

<ListBucketResult><Name>/testbucket</Name><Prefix/><ContinuationToken>key3</ContinuationToken><NextContinuationToken/><KeyCount>2</KeyCount><MaxKeys>2</MaxKeys><IsTruncated>false</IsTruncated><Contents><Key>key3</Key><LastModified>2019-06-18T14:26:43.081Z</LastModified><ETag></ETag><Size>27040</Size><StorageClass>STANDARD</StorageClass></Contents><Contents><Key>testobject</Key><LastModified>2019-06-18T14:24:33.029Z</LastModified><ETag></ETag><Size>27040</Size><StorageClass>STANDARD</StorageClass></Contents></ListBucketResult>

You can also verify those objects are represented as Alluxio files, under /testbucket directory.

./bin/alluxio fs ls -R /testbucket

-rw-r--r--  alluxio        staff                    27040       PERSISTED 06-18-2019 14:26:05:694 100% /testbucket/key1
-rw-r--r--  alluxio        staff                    27040       PERSISTED 06-18-2019 14:26:28:153 100% /testbucket/key2
-rw-r--r--  alluxio        staff                    27040       PERSISTED 06-18-2019 14:26:43:081 100% /testbucket/key3
-rw-r--r--  alluxio        staff                    27040       PERSISTED 06-18-2019 14:24:33:029 100% /testbucket/testobject

Delete objects

# curl -i -X DELETE http://localhost:39999/api/v1/s3/testbucket/key1

HTTP/1.1 204 No Content
Date: Tue, 18 Jun 2019 21:31:27 GMT
Server: Jetty(9.2.z-SNAPSHOT)
# curl -i -X DELETE http://localhost:39999/api/v1/s3/testbucket/key2

HTTP/1.1 204 No Content
Date: Tue, 18 Jun 2019 21:31:44 GMT
Server: Jetty(9.2.z-SNAPSHOT)

# curl -i -X DELETE http://localhost:39999/api/v1/s3/testbucket/key3

HTTP/1.1 204 No Content
Date: Tue, 18 Jun 2019 21:31:58 GMT
Server: Jetty(9.2.z-SNAPSHOT)

# curl -i -X DELETE http://localhost:39999/api/v1/s3/testbucket/testobject

HTTP/1.1 204 No Content
Date: Tue, 18 Jun 2019 21:32:08 GMT
Server: Jetty(9.2.z-SNAPSHOT)

Initiate a multipart upload

# curl -i -X POST http://localhost:39999/api/v1/s3/testbucket/testobject?uploads

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:32:36 GMT
Content-Type: application/xml
Content-Length: 133
Server: Jetty(9.2.z-SNAPSHOT)

<InitiateMultipartUploadResult><Bucket>testbucket</Bucket><Key>testobject</Key><UploadId>3</UploadId></InitiateMultipartUploadResult>

Note that the commands below related to multipart upload need the upload ID shown above, it’s not necessarily 3.

Upload part

# curl -i -X PUT 'http://localhost:39999/api/v1/s3/testbucket/testobject?partNumber=1&uploadId=3'

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:33:36 GMT
ETag: "d41d8cd98f00b204e9800998ecf8427e"
Content-Length: 0
Server: Jetty(9.2.z-SNAPSHOT)

List parts

# curl -i -X GET http://localhost:39999/api/v1/s3/testbucket/testobject?uploadId=3

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:35:10 GMT
Content-Type: application/xml
Content-Length: 296
Server: Jetty(9.2.z-SNAPSHOT)

<ListPartsResult><Bucket>/testbucket</Bucket><Key>testobject</Key><UploadId>3</UploadId><StorageClass>STANDARD</StorageClass><IsTruncated>false</IsTruncated><Part><PartNumber>1</PartNumber><LastModified>2019-06-18T14:33:36.373Z</LastModified><ETag>""</ETag><Size>0</Size></Part></ListPartsResult>

Complete a multipart upload

# curl -i -X POST http://localhost:39999/api/v1/s3/testbucket/testobject?uploadId=3

HTTP/1.1 200 OK
Date: Tue, 18 Jun 2019 21:35:47 GMT
Content-Type: application/xml
Content-Length: 201
Server: Jetty(9.2.z-SNAPSHOT)

<CompleteMultipartUploadResult><Location>/testbucket/testobject</Location><Bucket>testbucket</Bucket><Key>testobject</Key><ETag>"d41d8cd98f00b204e9800998ecf8427e"</ETag></CompleteMultipartUploadResult>

Abort a multipart upload

A non-completed upload can be aborted:

# curl -i -X DELETE http://localhost:39999/api/v1/s3/testbucket/testobject?uploadId=3

HTTP/1.1 204 No Content
Date: Tue, 18 Jun 2019 21:37:27 GMT
Server: Jetty(9.2.z-SNAPSHOT)

Delete an empty bucket

# curl -i -X DELETE http://localhost:39999/api/v1/s3/testbucket

HTTP/1.1 204 No Content
Date: Tue, 18 Jun 2019 21:38:38 GMT
Server: Jetty(9.2.z-SNAPSHOT)

Python S3 Client

Tested for Python 2.7.

Create a connection:

import boto
import boto.s3.connection

conn = boto.connect_s3(
    aws_access_key_id = '',
    aws_secret_access_key = '',
    host = 'localhost',
    port = 39999,
    path = '/api/v1/s3',
    is_secure=False,
    calling_format = boto.s3.connection.OrdinaryCallingFormat(),
)

Create a bucket

bucketName = 'bucket-for-testing'
bucket = conn.create_bucket(bucketName)

PUT a small object

smallObjectKey = 'small.txt'
smallObjectContent = 'Hello World!'

key = bucket.new_key(smallObjectKey)
key.set_contents_from_string(smallObjectContent)

Get the small object

assert smallObjectContent == key.get_contents_as_string()

Upload a large object

Create a 8MB file on local file system.

# dd if=/dev/zero of=8mb.data bs=1048576 count=8

Then use python S3 client to upload this as an object

largeObjectKey = 'large.txt'
largeObjectFile = '8mb.data'

key = bucket.new_key(largeObjectKey)
with open(largeObjectFile, 'rb') as f:
    key.set_contents_from_file(f)
with open(largeObjectFile, 'rb') as f:
    largeObject = f.read()

Get the large object

assert largeObject == key.get_contents_as_string()

Delete the objects

bucket.delete_key(smallObjectKey)
bucket.delete_key(largeObjectKey)

Initiate a multipart upload

mp = bucket.initiate_multipart_upload(largeObjectKey)

Upload parts

import math, os

from filechunkio import FileChunkIO

# Use a chunk size of 1MB (feel free to change this)
sourceSize = os.stat(largeObjectFile).st_size
chunkSize = 1048576
chunkCount = int(math.ceil(sourceSize / float(chunkSize)))

for i in range(chunkCount):
    offset = chunkSize * i
    bytes = min(chunkSize, sourceSize - offset)
    with FileChunkIO(largeObjectFile, 'r', offset=offset, bytes=bytes) as fp:
        mp.upload_part_from_file(fp, part_num=i + 1)

Complete the multipart upload

mp.complete_upload()

Abort the multipart upload

Non-completed uploads can be aborted.

mp.cancel_upload()

Delete the bucket

bucket.delete_key(largeObjectKey)
conn.delete_bucket(bucketName)