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Add this line to your application's Gemfile:

gem 'fog-aws'

And then execute:

$ bundle

Or install it yourself as:

$ gem install fog-aws


Before you can use fog-aws, you must require it in your application:

require 'fog/aws'

Since it's a bad practice to have your credentials in source code, you should load them from default fog configuration file: ~/.fog. This file could look like this:

  aws_access_key_id:     <YOUR_ACCESS_KEY_ID>
  aws_secret_access_key: <YOUR_SECRET_ACCESS_KEY>


Connecting to the EC2 Service:

ec2 = :provider => 'AWS', :region => 'us-west-2'

You can review all the requests available with this service using #requests method:

ec2.requests # => [:allocate_address, :assign_private_ip_addresses, :associate_address, ...]

Launch an EC2 on-demand instance:

response = ec2.run_instances(
  "InstanceType"  => "t1.micro",
  "SecurityGroup" => "ssh",
  "KeyName"       => "miguel"
instance_id = response.body["instancesSet"].first["instanceId"] # => "i-02db5af4"
instance = ec2.servers.get(instance_id)
instance.wait_for { ready? }
puts instance.public_ip_address # => "356.300.501.20"

Terminate an EC2 instance:

instance = ec2.servers.get("i-02db5af4")

Fog::AWS is more than EC2 since it supports many services provided by AWS. The best way to learn and to know about how many services are supported is to take a look at the source code. To review the tests directory and to play with the library in bin/console can be very helpful resources as well.


Connecting to the S3 Service:

s3 = 'AWS', region: 'eu-central-1')

Creating a file:

directory = 'gaudi-portal-dev')
file = directory.files.create(key: 'user/1/Gemfile', body:'Gemfile'), tags: 'Org-Id=1&Service-Name=My-Service')

Listing files:

directory = s3.directories.get('gaudi-portal-dev', prefix: 'user/1/')

Warning! s3.directories.get retrieves and caches meta data for the first 10,000 objects in the bucket, which can be very expensive. When possible use

Generating a URL for a file: 'user/1/Gemfile').url( + 60)
Controlling credential refresh time with IAM authentication

When using IAM authentication with temporary security credentials, generated S3 pre-signed URLs only last as long as the temporary credential.

Generating the URLs in the following manner will return a URL that will not last as long as its requested expiration time if the remainder of the authentication token lifetime was shorter.

s3 = 'AWS', use_iam_auth: true)
directory = s3.directories.get('gaudi-portal-dev', prefix: 'user/1/') 'user/1/Gemfile').url( + 60)

By default the temporary credentials in use are refreshed only within the last 15 seconds of its expiration time. The URL requested with 60 seconds lifetime using the above example will only remain valid for 15 seconds in the worst case.

The problem can be avoided by refreshing the token early and often, by setting configuration aws_credentials_refresh_threshold_seconds (default: 15) which controls the time when the refresh must occur. It is expressed in seconds before the temporary credential's expiration time.

The following example can ensure pre-signed URLs last as long as 60 seconds by automatically refreshing the credentials when its remainder lifetime is lower than 60 seconds:

s3 =
  provider: 'AWS',
  use_iam_auth: true,
  aws_credentials_refresh_threshold_seconds: 60
directory = s3.directories.get('gaudi-portal-dev', prefix: 'user/1/') 'user/1/Gemfile').url( + 60)

Copying a file

directory = 'gaudi-portal-dev')
file = directory.files.get('user/1/Gemfile')
file.copy("target-bucket", "user/2/Gemfile.copy")

To speed transfers of large files, the concurrency option can be used to spawn multiple threads. Note that the file must be at least 5 MB for multipart uploads to work. For example:

directory = 'gaudi-portal-dev')
file = directory.files.get('user/1/Gemfile')
file.multipart_chunk_size = 10 * 1024 * 1024
file.concurrency = 10
file.copy("target-bucket", "user/2/Gemfile.copy")


See the online documentation for a complete API reference.


After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.


  1. Fork it ( )
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request