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2.x-DSL-Action-File-Transfer-Download.md

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Definition

download(from, to, options={}, &block)

Module

Capistrano::Configuration::Actions::FileTransfer

The download action is used to transfer files (or even entire directory trees, though that'll be slow) from (potentially multiple) remote hosts to the local host, in parallel. It may be configured to use either SFTP or SCP to copy the files, defaulting to SFTP.

Note that because this helper uses the SCP and SFTP protocols, it isn't possible to sudo. You need to make sure that the user you are logging into the server(s) as has the necessary permissions to read the files.

Arguments

from

This must be a string indicating the path on the remote server that should be downloaded from. It may include the string $CAPISTRANO:HOST$, which will be replaced with the actual host name when the file is downloaded.

download("/etc/hosts", ...)
download("/usr/local/nginx/conf/server-$CAPISTRANO:HOST$.conf", ...)

to

This is a string identifying a file or directory name on the local host that you want to download the data to. It may include the special string $CAPISTRANO:HOST$, which will be replaced with the actual host name of the server being downloaded from. In fact, if you are downloading from multiple hosts simultaneously, you almost have to use $CAPISTRANO:HOST$ is the destination name, otherwise the servers will all be writing to the same file and you'll get a mess (if it works at all). By including the host name in the destination file, you can download each server's version of the file to a separate file locally.

download("/etc/hosts", "downloads/hosts-$CAPISTRANO:HOST$")

options

The options hash can be used to modify the default behavior of download. Recognized options are:

  • :mode This should a string indicating the desired permissions of the destination file or directory, after it is downloaded. Permissions are changed via a separate call to chmod, so any valid argument to chmod will work (either octal numbers or symbolic permissions).
  • :via This is a symbol indicating which protocol should be used to transfer the file or directory. If given, it must be either :sftp (the default), or :scp.
  • :hosts Either a string (for a single target host) or an array of strings, indicating which hosts should be downloaded to. By default, the hosts are determined from current task's roles.
  • :roles Either a string or symbol (for a single target role) or an array of strings or symbols, indicating which roles should be downloaded to. If :hosts is specified, :roles will be ignored. By default, the roles are taken from the current task.
  • :only Specifies a condition limiting which hosts will be selected to receive the download. This should refer to values set in the role. For example, if a role is defined with :primary => true, then you could select only hosts with that setting by specifying :only => { :primary => true }.
  • :except Specifies a condition limiting which hosts will be selected to receive the download. This is the inverse of :only (hosts that do not match the condition will be selected).
  • :once If true, only the first matching server will be selected. The default is false (all matching servers will be selected).
  • :recursive If true, a recursive download will be made. Use it with :via => :scp. The default is false.
  • :max_hosts Specifies the maximum number of hosts that should be selected at a time. If this value is less than the number of hosts that are selected to receive the download, then the hosts will be downloaded to in groups of max_hosts. The default is nil, which indicates that there is no maximum host limit. Warning: this setting will probably be removed in a future release.

Note that the options are also passed directly through to the Net::SFTP (for :sftp) and Net::SCP (for :scp) libraries. Options exposed by those libraries are documented in those libraries. (For SFTP, see the Net::SFTP::Operations::download module. For SCP, see the Net::SCP#download method.)

&block

If no block is passed to download, a minimal amount of progress reporting on the download will be provided by default. (You'll see when each file is sent to the server, and for SFTP, when transfer finishes.) However, if you pass a block, it will be called to report status on the progress of the download.

The format of the block is different, depending on whether you are using SFTP or SCP.

SFTP progress callbacks

For SFTP transfers, the block should take three parameters:

download("source", "target", :via => :sftp) do |event, options, *others|
  # ...
end

The event parameter is a symbol and will be indicate which event is being reported. It will be one of:

  • :open Indicates that a file is being opened in preparation for sending to the remote server. In this case, others[0] will be an object representing the file to be downloaded (see below).
  • :put Indicates that part (possibly all) of the current file is being downloaded. others[0] will be the file object (see below), others[1] will be the byte offset from which data is being sent, and others[2] will be the actual data being sent.
  • :close Indicates that a file has finished downloading. others[0] will be the file object (see below).
  • :mkdir This event is used to indicate that a remote directory is being created (as part of downloading a directory tree). others[0] is the remote path name in this case.
  • :finish Indicates that all files have been transferred for the current server.

The file object mentioned above is a simple structure with a few useful attributes. You can access object.local to get the local file name, object.remote to get the remote file name, and object.size to get the size of the file.

The options parameter is a hash of useful properties specific to the current server. It will contain at least the following keys:

  • :host The host name of the current server.
  • :server A Capistrano::ServerDefinition object for the current server.

The others parameter is an array of additional arguments, interpreted differently by the different progress events.

SCP progress callbacks

The SCP protocol doesn't give as much notification as the SFTP protocol does. In this case, the block takes four arguments:

download("source", "target", :via => :scp) do |channel, name, sent, total|
  # ...
end

Here, channel is the SSH channel over which the transfer is occurring. It can be used like a hash with the following keys:

  • :host The host name of the current server.
  • :server A Capistrano::ServerDefinition object for the current server.

The name argument is the name of the file being transferred. sent is the total number of bytes that have been sent so far for the file, and total is the full size of the file being transferred.