Configuring IOStreams


When using IOStreams.join it uses a default root from which to join the remainder of the path.

Set the default root for this environment

IOStreams.add_root(:default, "/var/my_app/files")

Now the default root path is available:

# => #<IOStreams::Paths::File:/var/my_app/files pipeline={}>
# => "/var/my_app/files"

Comparing the final path using path and then join that uses a root path:

IOStreams.path("/var/my_app/files", "my_test_file.txt").to_s
# => "/var/my_app/files/my_test_file.txt"

# => "/var/my_app/files/my_test_file.txt"

Using path:

IOStreams.path("/var/my_app/files", "my_test_file.txt").write("Hello World")

With the default root path configured the above code can be simplified by using join since it resolves to the same path.

IOStreams.join("my_test_file.txt").write("Hello World")

Other root paths can be added for special purposes.

For example add special paths for downloads and uploads.

IOStreams.add_root(:downloads, "/var/my_app/downloads")
IOStreams.add_root(:uploads, "/var/my_app/uploads")

An example that writes a file into the /var/my_app/downloads directory:

IOStreams.join("my_test_file.txt", root: :downloads).write("Hello World")

The other benefit is that the root paths used in an application are externalized from the code base. That way the roots can be changed to different locations depending on the environment.

We can also change the storage mechanism by changing the root:

IOStreams.add_root(:downloads, "s3://my-app-bucket-name/downloads")
IOStreams.add_root(:uploads, "s3://my-app-bucket-name/uploads")

Now the application will write to S3 and the code does not change at all.

IOStreams.join("my_test_file.txt", root: :downloads).write("Hello World")

To use or query a configured root path:

# => "s3://my-app-bucket-name/downloads"


When working with large files the standard temp file system location can be too small to handle downloading large files. For example to decrypt a pgp file from S3, because GnuPG is not streaming capable and only operates on local filess.

By default IOStreams looks up the location to store temp files in the following order:

To explicity set the temp file location the following config option can be used:

IOStreams.temp_dir = "/var/really_big_temp"