ssh_config: SSH Remote Launch Configuration

In mirai: Minimalist Async Evaluation Framework for R

SSH Remote Launch Configuration

Description

Generates a remote configuration for launching daemons over SSH, with the option of SSH tunnelling.

Usage

ssh_config(
  remotes,
  tunnel = FALSE,
  timeout = 10,
  command = "ssh",
  rscript = "Rscript"
)

Arguments

remotes	the character URL or vector of URLs to SSH into, using the 'ssh://' scheme and including the port open for SSH connections (defaults to 22 if not specified), e.g. 'ssh://10.75.32.90:22' or 'ssh://nodename'.
tunnel	[default FALSE] logical value, whether to use SSH tunnelling. If TRUE, requires the daemons() url hostname to be '127.0.0.1'. See the 'SSH Tunnelling' section below for further details.
timeout	[default 10] maximum time allowed for connection setup in seconds.
command	the command used to effect the daemon launch on the remote machine as a character string (e.g. "ssh"). Defaults to "ssh" for ssh_config, although may be substituted for the full path to a specific SSH application. The default NULL for remote_config does not carry out any launches, but causes launch_remote() to return the shell commands for manual deployment on remote machines.
rscript	[default "Rscript"] assumes the R executable is on the search path. Replace with the full path of the Rscript executable on the remote machine if necessary. If launching on Windows, "Rscript" should be replaced with "Rscript.exe".

Value

A list in the required format to be supplied to the remote argument of daemons() or launch_remote().

SSH Direct Connections

The simplest use of SSH is to execute the daemon launch command on a remote machine, for it to dial back to the host / dispatcher URL.

It is assumed that SSH key-based authentication is already in place. The relevant port on the host must also be open to inbound connections from the remote machine, and is hence suitable for use within trusted networks.

SSH Tunnelling

Use of SSH tunnelling provides a convenient way to launch remote daemons without requiring the remote machine to be able to access the host. Often firewall configurations or security policies may prevent opening a port to accept outside connections.

In these cases SSH tunnelling offers a solution by creating a tunnel once the initial SSH connection is made. For simplicity, this SSH tunnelling implementation uses the same port on both host and daemon. SSH key-based authentication must already be in place, but no other configuration is required.

To use tunnelling, set the hostname of the daemons() url argument to be '127.0.0.1'. Using local_url() with tcp = TRUE also does this for you. Specifying a specific port to use is optional, with a random ephemeral port assigned otherwise. For example, specifying 'tcp://127.0.0.1:5555' uses the local port '5555' to create the tunnel on each machine. The host listens to '127.0.0.1:5555' on its machine and the remotes each dial into '127.0.0.1:5555' on their own respective machines.

This provides a means of launching daemons on any machine you are able to access via SSH, be it on the local network or the cloud.

See Also

cluster_config() for cluster resource manager launch configurations, or remote_config() for generic configurations.

Examples

# direct SSH example
ssh_config(c("ssh://10.75.32.90:222", "ssh://nodename"), timeout = 5)

# SSH tunnelling example
ssh_config(c("ssh://10.75.32.90:222", "ssh://nodename"), tunnel = TRUE)

## Not run: 

# launch 2 daemons on the remote machines 10.75.32.90 and 10.75.32.91 using
# SSH, connecting back directly to the host URL over a TLS connection:
daemons(
  url = host_url(tls = TRUE),
  remote = ssh_config(c("ssh://10.75.32.90:222", "ssh://10.75.32.91:222"))
)

# launch 2 daemons on the remote machine 10.75.32.90 using SSH tunnelling:
daemons(
  n = 2,
  url = local_url(tcp = TRUE),
  remote = ssh_config("ssh://10.75.32.90", tunnel = TRUE)
)

## End(Not run)

mirai documentation built on June 26, 2025, 1:08 a.m.