File Transfer Protocol (FTP)

Cromwell supports communication with basic FTP servers (not FTPS, and not SFTP either). Please read the #Filesystems section before to get an explanation of how filesystems can be configured in general. For a full example of FTP configuration see here

Note: Be aware that FTP is in many cases very inefficient, not secure and generally doesn't scale well. If possible, consider using an alternate file system.

Overview

Cromwell handles FTP connections as follows:

  • Cromwell maintains one FTP FileSystem per FTP server per user
  • An FTP FileSystem maintains a pool of connections with a fixed size (see max-connection-per-server-per-user configuration below) to that server, for that user
  • When an FTP FileSystem hasn't been used in a certain amount of time (see cache-ttl configuration below), the associated connections are closed and it is destroyed
  • In a given pool, when a connection has been idle for a certain amount of time (see idle-connection-timeout configuration below), it is closed
 Cromwell
+---------------------------------------------------------------------------------------------------+
|                                                                                                   |
|  FileSystem 1                     FileSystem 2                     FileSystem 3                   |
| +-----------------------------+  +-----------------------------+  +-----------------------------+ |
| |                             |  |                             |  |                             | |
| | ftp://[email protected]     |  | ftp://[email protected]     |  | ftp://[email protected]     | |
| |                             |  |                             |  |                             | |
| |  Connection Pool            |  |  Connection Pool            |  |  Connection Pool            | |
| | +-------------------------+ |  | +-------------------------+ |  | +-------------------------+ | |
| | |                         | |  | |                         | |  | |                         | | |
| | |  - Connection 1         | |  | |  - Connection 1         | |  | |  - Connection 1         | | |
| | |                         | |  | |                         | |  | |                         | | |
| | |  - Connection 2         | |  | |  - Connection 2         | |  | |  - Connection 2         | | |
| | |                         | |  | |                         | |  | |                         | | |
| | |  - Connection 3         | |  | |  - Connection 3         | |  | |  - Connection 3         | | |
| | |                         | |  | |                         | |  | |                         | | |
| | +-------------------------+ |  | +-------------------------+ |  | +-------------------------+ | |
| |                             |  |                             |  |                             | |
| +-----------------------------+  +-----------------------------+  +-----------------------------+ |
+---------------------------------------------------------------------------------------------------+

Global Configuration

The FTP filesystem supports a global configuration. The goal is to configure values that will apply Cromwell-wide, as opposed to other configuration that could be backend (or engine) specific (see below).

Default configuration:

filesystems.ftp.global.config = {
    # This value should be sufficiently high to cover for the duration of the longest expected I/O operation.
    # It is a time to live value after which a filesystem (unique per user per server) will be closed and evicted from the cache if unused for the specified duration.
    cache-ttl = 1 day

    # How long to wait trying to obtain a connection from the pool before giving up. Don't specify for no timeout
    # obtain-connection-timeout = 1 hour

    # Maximum number of connections that will be established per user per ftp server. This is across the entire Cromwell instance.
    # Setting this number allows to workaround FTP server restrictions for the number of connections for a single user per IP address.
    # Has to be >= 2 to allow copying (Copying and FTP file requires downloading and uploading it)
    max-connection-per-server-per-user = 30

    # Time after which a connection will be closed if idle. This is to try to free connections from a filesystem when it's not heavily used.
    idle-connection-timeout = 1 hour

    # FTP connection port to use
    connection-port: 21

    # FTP connection mode
    connection-mode = "passive"
}

Note that this configuration being global, it applies the same way regardless of the FTP server. There is currently no good way to make this configuration dependent on the server.

Instance Configuration

Configuration that can be applied to a backend or engine filesystem stanza:

ftp {
  # optional
  auth {
    username = "username"
    password = "password"
    # Optional
    account = "account"
  }
}

A default authentication can be provided in the configuration. It can be overridden using the following workflow options: ftp-username, ftp-password, ftp-account If authentication is omitted the connection is established as an anonymous user.

Example

Example of configuration mixing the above two sections:

filesystems.ftp.global.config {
    # We only override what changes from the default
    max-connection-per-server-per-user = 20
}

# Configure the default auth for the engine
engine.filesystems.ftp {
  auth {
    username = "me"
    password = "my_password"
  }
}

# Configure the default auth for the local backend
backend.providers.Local.config.filesystems.ftp {
  auth {
    username = "me"
    password = "my_password"
  }
}