Add metadata to get, fget and get_partial methods

[DrJackilD]

Regard to this issue: #521 I want to add support for additional headers in get methods.

[harshavardhana]

Are you sure this is what you want to do? GET doesn't upload any object in-fact it downloads the object. How does adding another parameter to fget_object help here? .

[DrJackilD]

As example I can provide a case, when you using SSE-C and want to provide custom headers to get decrypted file from S3:

    key = b'32byteslongsecretkeymustprovided'
    encryption_key = base64.b64encode(key).decode()
    encryption_key_md5 = base64.b64encode(hashlib.md5(key).digest()).decode()

    minio = Minio('s3.amazonaws.com', access_key=AWSAccessKeyId, secret_key=AWSSecretKey)

    obj = minio.get_object(S3_BUCKET, 'test_crypt.txt', metadata={
        'x-amz-server-side-encryption-customer-algorithm': 'AES256',
        'x-amz-server-side-encryption-customer-key': encryption_key,
        'x-amz-server-side-encryption-customer-key-MD5': encryption_key_md5
    })

    print(obj.read())

    minio.put_object(S3_BUCKET, 'test_crypt1.txt', content, content.getbuffer().nbytes,
                     metadata={
                         'x-amz-server-side-encryption-customer-algorithm': 'AES256',
                         'x-amz-server-side-encryption-customer-key': encryption_key,
                         'x-amz-server-side-encryption-customer-key-MD5': encryption_key_md5
                     })

    obj = minio.get_object(S3_BUCKET, 'test_crypt1.txt', metadata={
        'x-amz-server-side-encryption-customer-algorithm': 'AES256',
        'x-amz-server-side-encryption-customer-key': encryption_key,
        'x-amz-server-side-encryption-customer-key-MD5': encryption_key_md5
    })

    print(obj.read())

[harshavardhana]

key = b'32byteslongsecretkeymustprovided'
encryption_key = base64.b64encode(key).decode()
encryption_key_md5 = base64.b64encode(hashlib.md5(key).digest()).decode()

minio = Minio('s3.amazonaws.com', access_key=AWSAccessKeyId, secret_key=AWSSecretKey)

obj = minio.get_object('minio-vfs-test', 'test_crypt.txt', metadata={
    'x-amz-server-side-encryption-customer-algorithm': 'AES256',
    'x-amz-server-side-encryption-customer-key': encryption_key,
    'x-amz-server-side-encryption-customer-key-MD5': encryption_key_md5
})

print(obj.read())

minio.put_object('minio-vfs-test', 'test_crypt1.txt', content, content.getbuffer().nbytes,
                 metadata={
                     'x-amz-server-side-encryption-customer-algorithm': 'AES256',
                     'x-amz-server-side-encryption-customer-key': encryption_key,
                     'x-amz-server-side-encryption-customer-key-MD5': encryption_key_md5
                 })

obj = minio.get_object('minio-vfs-test', 'test_crypt1.txt', metadata={
    'x-amz-server-side-encryption-customer-algorithm': 'AES256',
    'x-amz-server-side-encryption-customer-key': encryption_key,
    'x-amz-server-side-encryption-customer-key-MD5': encryption_key_md5
})

print(obj.read())

Then perhaps you need to update the comment.. to reflect the right purpose here. Rather than saying upload we should say that these are request headers.. and not metadata but rather just request_headers . Since these are request_headers http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectGET.html#get-object-sse-c-specific-request-headers

With this we can also support now 'If-Match', 'If-Modified-Since' etc.

Additionally it would be cleaner to get a full example added as well to examples/

[DrJackilD]

@harshavardhana I'm agreed, that request_headers will be cleaner, I'm just take same name, as in the put_object, where this variable in fact just additional headers too. So, I suggest to left it as is, to be consistent with other methods. Agreed?

P. S. Also I saw that CI was failed, I'm looking what's happened now

[DrJackilD]

Tests fixed and documentation is updated with example of usage

[harshavardhana]

IMHO we should keep it as request headers, in put_object it is meant to be saved with the object. Here it is meant to be queried.. so it is better to named request_headers or req_headers makes the code more readable.

[DrJackilD]

Ok, agreed, I will rename it right now :)

[harshavardhana]

Tested with If-Match, If-Modified-Since.. LGTM

[DrJackilD]

@harshavardhana So, as far as you approved this PR, when I could expect this on the master branch? I want to use it in my project :)