Setting up file and image uploads to S3

So, you want to use S3 to handle image uploads? Here’s the definitive guide:

S3 registration

Head over to https://aws.amazon.com/free/ and click on Create a Free Account

During the create account process, make sure you provide payment information, otherwise you won’t be able to use S3. There’s no registration fee, you will only be charged for what you use, if you exceed the AWS Free Usage Tier.

Bucket

Go to S3 and click on Create bucket, then fill out the Bucket name. Remember this name because we’ll need it for the next step.

Name of your bucket

Select a Region. You should enter the location (eg. “EU (Frankfurt)”) that is nearest to your users for better performance.

Scroll down a little until you get to the Permissions panel.

  • When you set up the permissions, make sure that you allow public ACLs, otherwise uploads will fail. Uncheck Block all public access and check the bottom two checkboxes. You’ll also have to acknowledge that your settings may make the bucket public in the warning at the top.

User creation

Creating a policy

Sign in to AWS Management Console and search for the “IAM” service to access the AWS Identity and Access Management (IAM) console which enables you to manage access to your AWS resources.

First, click Policies in the sidebar. Then, click on Create Policy and choose the JSON tab:

image

Use the following piece of code as a template for your policy document:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
               "s3:List*",
               "s3:Get*",
               "s3:AbortMultipartUpload",
               "s3:DeleteObject",
               "s3:PutObject",
               "s3:PutObjectAcl",
               "s3:PutObjectVersionAcl",
               "s3:PutLifecycleConfiguration",
               "s3:CreateBucket",
               "s3:PutBucketCORS"
      ],
      "Resource": [
        "arn:aws:s3:::name-of-your-uploads-bucket",
        "arn:aws:s3:::name-of-your-uploads-bucket/*"
      ]
    },
    {
       "Effect": "Allow",
       "Action": [
           "s3:ListAllMyBuckets",
           "s3:HeadBucket"
       ],
       "Resource": "*"
    }
  ]
}

:warning: Make sure that these two lines contain the actual name of your bucket. :blush:

image

:star2: If you also intend to do S3 backups, you can include your backup bucket here too like this:

image

Then click on Review Policy and fill out the Name field. For example, you can call it s3-discourse-policy

Then click on Create Policy at the bottom.

Creating a user account

Now that you’ve created the right policy, you’re ready to create the user account. Click on the Users link on the left side of the IAM console and then the Add user button.

Type in a descriptive user name and make sure the “Programmatic access” checkbox is checked.

Setting permissions

The next step in the process is to configure the user’s permissions. Click on the button that says Next: Permissions and then click on «Attach existing policies directly»:
image

Now search for the policy name you created in the previous step (in our case it’s s3-discourse-policy). When you find it, select the checkbox and click on Next: Tags, then Next: Review, then finally Create user.

Here’s the critical step: Make sure you either download the credentials (Download .csv) or you copy and paste somewhere safe both Access key ID and Secret access key values. We will need them in the next step.

Discourse configuration

Now that you’ve properly set up S3, the final step is to configure your Discourse forum. These instructions should work, but the preferred method is to use environment variables and a CDN as described in Using Object Storage for Uploads (S3 & Clones).

Make sure you’re logged in with an administrator account and go the Settings section in the admin panel.

Type in “S3” in the textbox on the right to display only the relevant settings:

You will need to:

  • Check the “enable s3 uploads” checkbox to activate the feature
  • Paste in both “Access Key Id” and “Secret Access Key” in their respective text fields
  • Enter =BUCKET= in the “s3 upload bucket” field

You need to append a prefix to the bucket name if you want to use the same bucket for uploads and backups.

Examples of valid bucket settings
  1. Different buckets

    • s3_upload_bucket: =BUCKET=
    • s3_backup_bucket: =BACKUPS=
  2. Different prefixes

    • s3_upload_bucket: =BUCKET=/uploads
    • s3_backup_bucket: =BUCKET=/backups
  3. Prefix for backups

    • s3_upload_bucket: =BUCKET=
    • s3_backup_bucket: =BUCKET=/backups

The “s3_region” setting is optional and defaults to “US East (N. Virginia)”. You should enter the location (eg. “EU (Frankfurt)”) that is nearest to your users for better performance. If you created the bucket manually, you’ll need to select the region you selected during the creation process.

Enjoy

That’s it. From now on, all your images will be uploaded to and served from S3.

Backups

Do you want store backups of your Discourse forum on S3 as well? Take a look at Configure automatic backups for Discourse.

Frequently Asked Questions

I reused the same bucket for uploads and backups and now backups aren’t working. What should I do?

Name of your bucket for backups

The easiest solution is to append a path to the s3_backup_bucket. Here’s an example of how your settings should look afterwards.

  • s3_upload_bucket: =BACKUPS=
  • s3_backup_bucket: =BACKUPS=/backups

You can use the S3 Console to move existing backups into the new folder.

Do I really need to use separate buckets for uploads and backups?

No, you don’t, but it’s usually the easiest way to set-up. Essentially you need to either use two different buckets or a prefix for the backup bucket. For example, the following combinations will work:

  1. Different buckets

    • s3_upload_bucket: =BUCKET=
    • s3_backup_bucket: =BACKUPS=
  2. Different prefixes

    • s3_upload_bucket: =BUCKET=/uploads
    • s3_backup_bucket: =BUCKET=/backups
  3. Prefix for backups (not recommended unless you previously reused the same bucket – see above question)

    • s3_upload_bucket: =BACKUPS=
    • s3_backup_bucket: =BACKUPS=/backups

I've enabled S3 uploads in my Discourse instance (which has been going for a while); what do I do with the existing local uploads?

To migrate your existing uploads to S3, you can do a couple of rake tasks. To perform this, you need SSH access, root permissions, and have entered the discourse app (as per Administrative Bulk Operations). Oh, and you have to set some environmental variables in app.yml. Not for the faint-hearted.

Once you have done all that you are ready for the rake tasks:

rake uploads:migrate_to_s3
rake posts:rebake

Once these are done (and the uploads are working well) you no longer need to include uploads in your backups. And as a bonus, you will be able to Restore a backup from command line in the event of catastrophe (just keep a copy of app.yml somewhere).

One-way door

Unlike many configuration decisions in Discourse, note that using S3 is a “one-way door;” that is, a move that cannot easily be reversed. There is no safe or maintained way to move files out of S3 to be in the local uploads. In particular, the migrate_to_s3 moves more than just post images to S3; files for which there is no reverse path. (For more details, see Migrate_from_s3 problems)

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I just went through:

  • Setting up S3 using IAM user & the policy outlined above
  • Setting up Cloudfront distribution pointing to S3 bucket, along with custom CDN domain + SSL cert
  • Rebaked all posts using cd /var/www/discourse && ./launcher enter app && rake posts:rebake (yes, I’m too OCD to not put discourse under www :wink: ).

A few gotchas in case they’re useful to someone:

  • Got a permission denied when I tried to get Discourse to create the bucket - reason? I was using too generic a name (forum-media) and it was denying the create request. I switched it to something unique within the IAM user, Discourse config, and it worked as expected. Can the permission denied error be more granular so users know that that bucket name is not available?
  • AWS Cloudfront doesn’t do a good job telling you how to configure the CNAME - it was fairly obvious when I saw the origin, but, just in case

Beautiful new forum now blossoming at https://forum.makesoil.org

6 Likes

The following should work:

  • create a database backup
  • move all objects to the new S3 bucket
  • execute discourse remap old_bucket_name new_bucket_name inside the docker container
7 Likes

One way to work out if this is a problem with the Access Keys and IAM stuff (as opposed to a Discourse issue) is to try to upload a simple file to AWS using the CLI GitHub - awslabs/aws-shell: An integrated shell for working with the AWS CLI. using those credentials. If they don’t work from the CLI then something’s wrong with the permissions applied to those keys.

I find that configuring an IAM user specifically for Discourse backups and uploads gives some nice compartmentalisation of concerns and additional security compared to using a user with global S3 bucket access policy, especially if you run multiple Discourses.

This snippet goes in the Access Control Policy which you will create, replacing <BUCKET_NAME> with your bucket name, and apply to your IAM user. It confers access ONLY to the named bucket you specify. Note that you need to be able to access the top level bucket name and it contents /*, and be able to ‘List All Buckets’.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "s3:ListAllMyBuckets",
            "Resource": "arn:aws:s3:::*"
        },
        {
            "Effect": "Allow",
            "Action": "s3:*",
            "Resource": [
                "arn:aws:s3:::<BUCKET_NAME>",
                "arn:aws:s3:::<BUCKET_NAME>/*"
            ]
        }
    ]
}
9 Likes

Glad it helped @deepmehtait

5 Likes

The problem has been fixed:

9 Likes

Updated guide to include placeholder forms, as it’s really easy to get confused with all the different bucket names!

8 Likes

The server needs to do some post-processing on the images, like generating thumbnails. By passing the upload through, it can perform the multiple S3 uploads instead of needing to do an upload/download/upload.

I guarantee that S3 is charging you more for downloads than the bandwidth on your server costs :wink:

5 Likes