Unable to set file content type in S3

StackOverflow https://stackoverflow.com/questions/21801706

  •  12-10-2022
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Question

How do you set content type on a file in a webhosting-enabled S3 account via the Python boto module?

I'm doing:

from boto.s3.connection import S3Connection
from boto.s3.key import Key
from boto.cloudfront import CloudFrontConnection

conn = S3Connection(access_key_id, secret_access_key)
bucket = conn.create_bucket('mybucket')
b = conn.get_bucket(bucket)
b.set_acl('public-read')

fn = 'index.html'
template = '<html>blah</html>'
k = Key(b)
k.key = fn
k.set_contents_from_string(template)
k.set_acl('public-read')
k.set_metadata('Content-Type', 'text/html')

However, when I access it from http://mybucket.s3-website-us-east-1.amazonaws.com/index.html my browser prompts me to download the file instead of simply serving it as a webpage.

Looking at the metadata in the S3 Management console shows the Content-Type has actually been set to "application/octet-stream". If I manually change it in the console, I can access the page normally, but if I run my script again, it resets it back to the wrong content type.

What am I doing wrong?

Was it helpful?

Solution

The set_metadata method is really for setting user metadata on S3 objects. Many of the standard HTTP metadata fields have first class attributes to represent them, e.g. content_type. Also, you want to set the metadata before you actually send the object to S3. Something like this should work:

import boto

conn = boto.connect_s3()
bucket = conn.get_bucket('mybucket')  # Assumes bucket already exists
key = bucket.new_key('mykey')
key.content_type = 'text/html'
key.set_contents_from_string(mystring, policy='public-read')

Note that you can set canned ACL policies at the time you write the object to S3 which saves having to make another API call.

OTHER TIPS

For people who need one-liner for this,

import boto3
s3 = boto3.resource('s3')

s3.Bucket('bucketName').put_object(Key='keyName', Body='content or fileData', ContentType='contentType', ACL='check below')

Supported ACL values:

'private'|'public-read'|'public-read-write'|'authenticated-read'|'aws-exec-read'|'bucket-owner-read'|'bucket-owner-full-control'

Arguments supported by put_object can be found here, https://boto3.readthedocs.io/en/latest/reference/services/s3.html#S3.Client.put_object

I wasn't able to get the above solution to actually persist my metadata changes.

Perhaps because I was using a file and it was resetting the content type using mimetype? Also I am uploading m3u8 and ts files for HLS encoding so that could interfere as well.

Anyway, here's what worked for me.

import boto
conn = boto.connect_s3()
bucket = conn.get_bucket('mybucket')
key_m3u8 = Key(bucket_handle)
key_m3u8.key = s3folder+"/"+s3keyname
key_m3u8.metadata = {"Content-Type":"application/x-mpegURL","Cache-Control":"public,max-age=8"}                             
key_m3u8.set_contents_from_filename("path_to_my_file", policy="public-read")

If you use AWS S3 Bitbucket Pipelines Python add the parameter content_type:

s3_upload.py

def upload_to_s3(bucket, artefact, bucket_key, content_type):
...

def main():
...
    parser.add_argument("content_type", help="Content Type File")
...

if not upload_to_s3(args.bucket, args.artefact, args.bucket_key, args.content_type):

then modify bitbucket-pipelines.yml as follow:

...
- python s3_upload.py bucket_name file key content_type 
...

Where content_type param can be one of the following: MIME types (IANA media types)

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