% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/makeClusterPSOCK.R
\name{makeClusterPSOCK}
\alias{makeClusterPSOCK}
\alias{makeNodePSOCK}
\title{Create a PSOCK Cluster of R Workers for Parallel Processing}
\usage{
makeClusterPSOCK(
  workers,
  makeNode = makeNodePSOCK,
  port = c("auto", "random"),
  ...,
  autoStop = FALSE,
  tries = getOptionOrEnvVar("future.makeNodePSOCK.tries", 3L),
  delay = getOptionOrEnvVar("future.makeNodePSOCK.tries.delay", 15),
  validate = getOptionOrEnvVar("future.makeNodePSOCK.validate", TRUE),
  verbose = getOptionOrEnvVar("future.debug", FALSE)
)

makeNodePSOCK(
  worker = "localhost",
  master = NULL,
  port,
  connectTimeout = getOptionOrEnvVar("future.makeNodePSOCK.connectTimeout", 2 * 60),
  timeout = getOptionOrEnvVar("future.makeNodePSOCK.timeout", 30 * 24 * 60 * 60),
  rscript = NULL,
  homogeneous = NULL,
  rscript_args = NULL,
  rscript_envs = NULL,
  rscript_libs = NULL,
  rscript_startup = NULL,
  methods = TRUE,
  useXDR = getOptionOrEnvVar("future.makeNodePSOCK.useXDR", FALSE),
  outfile = "/dev/null",
  renice = NA_integer_,
  rshcmd = getOptionOrEnvVar("future.makeNodePSOCK.rshcmd", NULL),
  user = NULL,
  revtunnel = TRUE,
  rshlogfile = NULL,
  rshopts = getOptionOrEnvVar("future.makeNodePSOCK.rshopts", NULL),
  rank = 1L,
  manual = FALSE,
  dryrun = FALSE,
  verbose = FALSE
)
}
\arguments{
\item{workers}{The hostnames of workers (as a character vector) or the number
of localhost workers (as a positive integer).}

\item{makeNode}{A function that creates a \code{"SOCKnode"} or
\code{"SOCK0node"} object, which represents a connection to a worker.}

\item{port}{The port number of the master used for communicating with all
the workers (via socket connections).  If an integer vector of ports, then a
random one among those is chosen.  If \code{"random"}, then a random port in
is chosen from \code{11000:11999}, or from the range specified by
environment variable \env{R_FUTURE_RANDOM_PORTS}.
If \code{"auto"} (default), then the default (single) port is taken from
environment variable \env{R_PARALLEL_PORT}, otherwise \code{"random"} is
used.
\emph{Note, do not use this argument to specify the port number used by
\code{rshcmd}, which typically is an SSH client.  Instead, if the SSH daemon
runs on a different port than the default 22, specify the SSH port by
appending it to the hostname, e.g. \code{"remote.server.org:2200"} or via
SSH options \code{-p}, e.g. \code{rshopts = c("-p", "2200")}.}}

\item{\dots}{Optional arguments passed to
\code{makeNode(workers[i], ..., rank = i)} where \code{i = seq_along(workers)}.}

\item{autoStop}{If TRUE, the cluster will be automatically stopped
using \code{\link[parallel:makeCluster]{stopCluster}()} when it is
garbage collected, unless already stopped.  See also \code{\link[=autoStopCluster]{autoStopCluster()}}.}

\item{tries, delay}{Maximum number of attempts done to launch each node
with \code{makeNode()} and the delay (in seconds) in-between attempts.
If argument \code{port} specifies more than one port, e.g. \code{port = "random"}
then a random port will be drawn and validated at most \code{tries} times.}

\item{validate}{If TRUE, after the nodes have been created, they are all
validated that they work by inquiring about their session information,
which is saved in attribute \code{session_info} of each node.}

\item{verbose}{If TRUE, informative messages are outputted.}

\item{worker}{The hostname or IP number of the machine where the worker
should run.}

\item{master}{The hostname or IP number of the master / calling machine, as
known to the workers.  If NULL (default), then the default is
\code{Sys.info()[["nodename"]]} unless \code{worker} is \emph{localhost} or
\code{revtunnel = TRUE} in case it is \code{"localhost"}.}

\item{connectTimeout}{The maximum time (in seconds) allowed for each socket
connection between the master and a worker to be established (defaults to
2 minutes). \emph{See note below on current lack of support on Linux and
macOS systems.}}

\item{timeout}{The maximum time (in seconds) allowed to pass without the
master and a worker communicate with each other (defaults to 30 days).}

\item{rscript, homogeneous}{The system command for launching \command{Rscript}
on the worker and whether it is installed in the same path as the calling
machine or not.  For more details, see below.}

\item{rscript_args}{Additional arguments to \command{Rscript} (as a character
vector).  This argument can be used to customize the \R environment of the
workers before they launches.
For instance, use \code{rscript_args = c("-e", shQuote('setwd("/path/to")'))}
to set the working directory to \file{/path/to} on \emph{all} workers.}

\item{rscript_envs}{A named character vector environment variables to
set on worker at startup, e.g.
\code{rscript_envs = c(FOO = "3.14", "HOME", "UNKNOWN")}.
If an element is not named, then the value of that variable will be used as
the name and the value will be the value of \code{Sys.getenv()} for that
variable.  Non-existing environment variables will be dropped.
These variables are set using \code{Sys.setenv()}.}

\item{rscript_libs}{A character vector of \R library paths that will be
used for the library search path of the \R workers.  An asterisk
(\code{"*"}) will be resolved to the default \code{.libPaths()} \emph{on the
worker}. That is, to \code{prepend} a folder, instead of replacing the
existing ones, use \code{rscript_libs = c("new_folder", "*")}.
To pass down a non-default library path currently set \emph{on the main \R
session} to the workers, use \code{rscript_libs = .libPaths()}.}

\item{rscript_startup}{An \R expression or a character vector of \R code,
or a list with a mix of these, that will be evaluated on the \R worker
prior to launching the worker's event loop.
For instance, use \code{rscript_startup = 'setwd("/path/to")'}
to set the working directory to \file{/path/to} on \emph{all} workers.}

\item{methods}{If TRUE, then the \pkg{methods} package is also loaded.}

\item{useXDR}{If TRUE, the communication between master and workers, which
is binary, will use big-endian (XDR).}

\item{outfile}{Where to direct the \link[base:showConnections]{stdout} and
\link[base:showConnections]{stderr} connection output from the workers.
If NULL, then no redirection of output is done, which means that the
output is relayed in the terminal on the local computer.  On Windows, the
output is only relayed when running \R from a terminal but not from a GUI.}

\item{renice}{A numerical 'niceness' (priority) to set for the worker
processes.}

\item{rshcmd, rshopts}{The command (character vector) to be run on the master
to launch a process on another host and any additional arguments (character
vector).  These arguments are only applied if \code{machine} is not
\emph{localhost}.  For more details, see below.}

\item{user}{(optional) The user name to be used when communicating with
another host.}

\item{revtunnel}{If TRUE, a reverse SSH tunnel is set up for each worker such#' that the worker \R process sets up a socket connection to its local port
\code{(port - rank + 1)} which then reaches the master on port \code{port}.
If FALSE, then the worker will try to connect directly to port \code{port} on
\code{master}.  For more details, see below.}

\item{rshlogfile}{(optional) If a filename, the output produced by the
\code{rshcmd} call is logged to this file, of if TRUE, then it is logged
to a temporary file.  The log file name is available as an attribute
as part of the return node object.
\emph{Warning: This only works with SSH clients that support option
\verb{-E out.log}.}}

\item{rank}{A unique one-based index for each worker (automatically set).}

\item{manual}{If TRUE the workers will need to be run manually. The command
to run will be displayed.}

\item{dryrun}{If TRUE, nothing is set up, but a message suggesting how to
launch the worker from the terminal is outputted.  This is useful for
troubleshooting.}
}
\value{
An object of class \code{c("RichSOCKcluster", "SOCKcluster", "cluster")}
consisting of a list of \code{"SOCKnode"} or \code{"SOCK0node"} workers (that also
inherit from \code{RichSOCKnode}).

\code{makeNodePSOCK()} returns a \code{"SOCKnode"} or
\code{"SOCK0node"} object representing an established connection to a worker.
}
\description{
The \code{makeClusterPSOCK()} function creates a cluster of \R workers
for parallel processing.  These \R workers may be background \R sessions
on the current machine, \R sessions on external machines (local or remote),
or a mix of such. For external workers, the default is to use SSH to connect
to those external machines.  This function works similarly to
\code{\link[parallel:makeCluster]{makePSOCKcluster}()} of the
\pkg{parallel} package, but provides additional and more flexibility options
for controlling the setup of the system calls that launch the background
\R workers, and how to connect to external machines.
}
\section{Definition of \emph{localhost}}{

A hostname is considered to be \emph{localhost} if it equals:
\itemize{
\item \code{"localhost"},
\item \code{"127.0.0.1"}, or
\item \code{Sys.info()[["nodename"]]}.
}
It is also considered \emph{localhost} if it appears on the same line
as the value of \code{Sys.info()[["nodename"]]} in file \file{/etc/hosts}.
}

\section{Default SSH client and options (arguments \code{rshcmd} and \code{rshopts})}{

Arguments \code{rshcmd} and \code{rshopts} are only used when connecting
to an external host.

The default method for connecting to an external host is via SSH and the
system executable for this is given by argument \code{rshcmd}.  The default
is given by option \option{future.makeNodePSOCK.rshcmd}.  If that is not
set, then the default is to use \command{ssh}.
Most Unix-like systems, including macOS, have \command{ssh} preinstalled
on the \env{PATH}.  This is also true for recent Windows 10
(since version 1803, April 2018) (*).

For \emph{Windows systems prior to Windows 10}, it is less common to find
\command{ssh} on the \env{PATH}. Instead it is more likely that such
systems have the \command{PuTTY} software and its SSH client
\command{plink} installed.  PuTTY puts itself on the system \env{PATH}
when installed, meaning this function will find PuTTY automatically if
installed.  If not, to manually set specify PuTTY as the SSH client,
specify the absolute pathname of \file{plink.exe} in the first element and
option \command{-ssh} in the second as in
\code{rshcmd = c("C:/Path/PuTTY/plink.exe", "-ssh")}.
This is because all elements of \code{rshcmd} are individually "shell"
quoted and element \code{rshcmd[1]} must be on the system \env{PATH}.

Furthermore, when running \R from RStudio on Windows, the \command{ssh}
client that is distributed with RStudio will also be considered.
This client, which is from \href{http://www.mingw.org/wiki/msys}{MinGW MSYS},
is searched for in the folder given by the \env{RSTUDIO_MSYS_SSH}
environment variable - a variable that is (only) set when running RStudio.

You can override the default set of SSH clients that are searched for
by specifying them in \code{rshcmd} using the format \verb{<...>}, e.g.
\code{rshcmd = c("<rstudio-ssh>", "<putty-plink>", "<ssh>")}.  See
below for examples.

If no SSH-client is found, an informative error message is produced.

(*) \emph{Known issue with the Windows 10 SSH client: There is a bug in the
SSH client of Windows 10 that prevents it to work with reverse SSH tunneling
(\url{https://github.com/PowerShell/Win32-OpenSSH/issues/1265}; Oct 2018).
The most recent version that we tested and that did \emph{not} work was
OpenSSH_for_Windows_7.7p1, LibreSSL 2.6.5 (\code{ssh -V}) on
Windows 10 (version 1909, OS build 18363.720) (\code{ver}).
Because of this, it is recommended to use the PuTTY SSH client or the
RStudio SSH client until this bug has been resolved in Windows 10.}

Additional SSH options may be specified via argument \code{rshopts}, which
defaults to option \option{future.makeNodePSOCK.rshopts}. For instance, a
private SSH key can be provided as
\code{rshopts = c("-i", "~/.ssh/my_private_key")}.  PuTTY users should
specify a PuTTY PPK file, e.g.
\code{rshopts = c("-i", "C:/Users/joe/.ssh/my_keys.ppk")}.
Contrary to \code{rshcmd}, elements of \code{rshopts} are not quoted.
}

\section{Accessing external machines that prompts for a password}{

\emph{IMPORTANT: With one exception, it is not possible to for these
functions to log in and launch \R workers on external machines that requires
a password to be entered manually for authentication.}
The only known exception is the PuTTY client on Windows for which one can
pass the password via command-line option \code{-pw}, e.g.
\code{rshopts = c("-pw", "MySecretPassword")}.

Note, depending on whether you run \R in a terminal or via a GUI, you might
not even see the password prompt.  It is also likely that you cannot enter
a password, because the connection is set up via a background system call.

The poor man's workaround for setup that requires a password is to manually
log into the each of the external machines and launch the \R workers by hand.
For this approach, use \code{manual = TRUE} and follow the instructions
which include cut'n'pasteable commands on how to launch the worker from the
external machine.

However, a much more convenient and less tedious method is to set up
key-based SSH authentication between your local machine and the external
machine(s), as explain below.
}

\section{Accessing external machines via key-based SSH authentication}{

The best approach to automatically launch \R workers on external machines
over SSH is to set up key-based SSH authentication.  This will allow you
to log into the external machine without have to enter a password.

Key-based SSH authentication is taken care of by the SSH client and not \R.
To configure this, see the manuals of your SSH client or search the web
for "ssh key authentication".
}

\section{Reverse SSH tunneling}{

The default is to use reverse SSH tunneling (\code{revtunnel = TRUE}) for
workers running on other machines.  This avoids the complication of
otherwise having to configure port forwarding in firewalls, which often
requires static IP address as well as privileges to edit the firewall,
something most users don't have.
It also has the advantage of not having to know the internal and / or the
public IP address / hostname of the master.
Yet another advantage is that there will be no need for a DNS lookup by the
worker machines to the master, which may not be configured or is disabled
on some systems, e.g. compute clusters.
}

\section{Argument \code{rscript}}{

If \code{homogeneous} is FALSE, the \code{rscript} defaults to \code{"Rscript"}, i.e. it
is assumed that the \command{Rscript} executable is available on the
\env{PATH} of the worker.
If \code{homogeneous} is TRUE, the \code{rscript} defaults to
\code{file.path(R.home("bin"), "Rscript")}, i.e. it is basically assumed that
the worker and the caller share the same file system and \R installation.

If specified, argument \code{rscript} should be a character vector with one more
more elements.
all elements are automatically shell quoted using \code{\link[base:shQuote]{base::shQuote()}}, except
those that are of format \verb{<ENVVAR>=<VALUE>}, that is, the ones matching the
regular expression '\samp{^[[:alpha:]_][[:alnum:]_]*=.*}'.
Another exception is when \code{rscript} inherits from 'AsIs'.
}

\section{Default value of argument \code{homogeneous}}{

The default value of \code{homogeneous} is TRUE if and only if either
of the following is fulfilled:
\itemize{
\item \code{worker} is \emph{localhost}
\item \code{revtunnel} is FALSE and \code{master} is \emph{localhost}
\item \code{worker} is neither an IP number nor a fully qualified domain
name (FQDN).  A hostname is considered to be a FQDN if it contains
one or more periods
}
In all other cases, \code{homogeneous} defaults to FALSE.
}

\section{Connection time out}{

Argument \code{connectTimeout} does \emph{not} work properly on Unix and
macOS due to limitation in \R itself.  For more details on this, please see
R-devel thread 'BUG?: On Linux setTimeLimit() fails to propagate timeout
error when it occurs (works on Windows)' on 2016-10-26
(\url{https://stat.ethz.ch/pipermail/r-devel/2016-October/073309.html}).
When used, the timeout will eventually trigger an error, but it won't happen
until the socket connection timeout \code{timeout} itself happens.
}

\section{Communication time out}{

If there is no communication between the master and a worker within the
\code{timeout} limit, then the corresponding socket connection will be
closed automatically.  This will eventually result in an error in code
trying to access the connection.
}

\section{Failing to set up local workers}{

When setting up a cluster of localhost workers, that is, workers running
on the same machine as the master \R process, occasionally a connection
to a worker ("cluster node") may fail to be set up.
When this occurs, an informative error message with troubleshooting
suggestions will be produced.
The most common reason for such localhost failures is due to port
clashes.  Retrying will often resolve the problem.
}

\section{Failing to set up remote workers}{

A cluster of remote workers runs \R processes on external machines. These
external \R processes are launched over, typically, SSH to the remote
machine.  For this to work, each of the remote machines needs to have
\R installed, which preferably is of the same version as what is on the
main machine.  For this to work, it is required that one can SSH to the
remote machines.  Ideally, the SSH connections use authentication based
on public-private SSH keys such that the set up of the remote workers can
be fully automated (see above).  If \code{makeClusterPSOCK()} fails to set
up one or more remote \R workers, then an informative error message is
produced.
There are a few reasons for failing to set up remote workers.  If this
happens, start by asserting that you can SSH to the remote machine and
launch \file{Rscript} by calling something like:
\preformatted{
{local}$ ssh -l alice remote.server.org
{remote}$ Rscript --version
R scripting front-end version 3.6.1 (2019-07-05)
{remote}$ logout
{local}$
}
When you have confirmed the above to work, then confirm that you can achieve
the same in a single command-line call;
\preformatted{
{local}$ ssh -l alice remote.server.org Rscript --version
R scripting front-end version 3.6.1 (2019-07-05)
{local}$
}
The latter will assert that you have proper startup configuration also for
\emph{non-interactive} shell sessions on the remote machine.

Another reason for failing to setup remote workers could be that they are
running an \R version that is not compatible with the version that your main
\R session is running.  For instance, if we run R (>= 3.6.0) locally and the
workers run R (< 3.5.0), we will get:
\verb{Error in unserialize(node$con) : error reading from connection}.
This is because R (>= 3.6.0) uses serialization format version 3 whereas
R (< 3.5.0) only supports version 2.  We can see the version of the \R
workers by adding \code{rscript_args = c("-e", shQuote("getRversion()"))} when
calling \code{makeClusterPSOCK()}.
}

\examples{
## NOTE: Drop 'dryrun = TRUE' below in order to actually connect.  Add
## 'verbose = TRUE' if you run into problems and need to troubleshoot.


## EXAMPLE: Two workers on the local machine
workers <- c("localhost", "localhost")
cl <- makeClusterPSOCK(workers, dryrun = TRUE)

## EXAMPLE: Three remote workers
## Setup of three R workers on two remote machines are set up
workers <- c("n1.remote.org", "n2.remote.org", "n1.remote.org")
cl <- makeClusterPSOCK(workers, dryrun = TRUE)


## EXAMPLE: Local and remote workers
## Same setup when the two machines are on the local network and
## have identical software setups
cl <- makeClusterPSOCK(
  workers,
  revtunnel = FALSE, homogeneous = TRUE,
  dryrun = TRUE
)

## EXAMPLE: Remote workers with specific setup
## Setup of remote worker with more detailed control on
## authentication and reverse SSH tunnelling
cl <- makeClusterPSOCK(
  "remote.server.org", user = "johnny",
  ## Manual configuration of reverse SSH tunnelling
  revtunnel = FALSE,
  rshopts = c("-v", "-R 11000:gateway:11942"),
  master = "gateway", port = 11942,
  ## Run Rscript nicely and skip any startup scripts
  rscript = c("nice", "/path/to/Rscript"),
  rscript_args = c("--vanilla"),
  dryrun = TRUE
)

## EXAMPLE: Two workers running in Docker on the local machine
## Setup of 2 Docker workers running rocker/r-parallel
cl <- makeClusterPSOCK(
  rep("localhost", times = 2L),
  ## Launch Rscript inside Docker container
  rscript = c(
    "docker", "run", "--net=host", "rocker/r-parallel",
    "Rscript"
  ),
  ## IMPORTANT: Because Docker runs inside a virtual machine (VM) on macOS
  ## and Windows (not Linux), when the R worker tries to connect back to
  ## the default 'localhost' it will fail, because the main R session is
  ## not running in the VM, but outside on the host.  To reach the host on
  ## macOS and Windows, make sure to use master = "host.docker.internal"
  # master = "host.docker.internal",  # <= macOS & Windows
  dryrun = TRUE
)


## EXAMPLE: Two workers running in Singularity on the local machine
## Setup of 2 Singularity workers running rocker/r-parallel
cl <- makeClusterPSOCK(
  rep("localhost", times = 2L),
  ## Launch Rscript inside Linux container
  rscript = c(
    "singularity", "exec", "docker://rocker/r-parallel",
    "Rscript"
  ),
  dryrun = TRUE
)


## EXAMPLE: One worker running in udocker on the local machine
## Setup of a single udocker.py worker running rocker/r-parallel
cl <- makeClusterPSOCK(
  "localhost",
  ## Launch Rscript inside Docker container (using udocker)
  rscript = c(
    "udocker.py", "run", "rocker/r-parallel",
    "Rscript"
  ), 
  ## Manually launch parallel workers
  ## (need double shQuote():s because udocker.py drops one level)
  rscript_args = c(
    "-e", shQuote(shQuote("parallel:::.slaveRSOCK()"))
  ),
  dryrun = TRUE
)


## EXAMPLE: Remote worker running on AWS
## Launching worker on Amazon AWS EC2 running one of the
## Amazon Machine Images (AMI) provided by RStudio
## (http://www.louisaslett.com/RStudio_AMI/)
public_ip <- "1.2.3.4"
ssh_private_key_file <- "~/.ssh/my-private-aws-key.pem"
cl <- makeClusterPSOCK(
  ## Public IP number of EC2 instance
  public_ip,
  ## User name (always 'ubuntu')
  user = "ubuntu",
  ## Use private SSH key registered with AWS
  rshopts = c(
    "-o", "StrictHostKeyChecking=no",
    "-o", "IdentitiesOnly=yes",
    "-i", ssh_private_key_file
  ),
  ## Set up .libPaths() for the 'ubuntu' user
  ## and then install the future package
  rscript_startup = quote(local({
    p <- Sys.getenv("R_LIBS_USER")
    dir.create(p, recursive = TRUE, showWarnings = FALSE)
    .libPaths(p)
    install.packages("future")
  })),
  dryrun = TRUE
)


## EXAMPLE: Remote worker running on GCE
## Launching worker on Google Cloud Engine (GCE) running a
## container based VM (with a #cloud-config specification)
public_ip <- "1.2.3.4"
user <- "johnny"
ssh_private_key_file <- "~/.ssh/google_compute_engine"
cl <- makeClusterPSOCK(
  ## Public IP number of GCE instance
  public_ip,
  ## User name (== SSH key label (sic!))
  user = user,
  ## Use private SSH key registered with GCE
  rshopts = c(
    "-o", "StrictHostKeyChecking=no",
    "-o", "IdentitiesOnly=yes",
    "-i", ssh_private_key_file
  ),
  ## Launch Rscript inside Docker container
  rscript = c(
    "docker", "run", "--net=host", "rocker/r-parallel",
    "Rscript"
  ),
  dryrun = TRUE
)


## EXAMPLE: Remote worker running on Linux from Windows machine
## Connect to remote Unix machine 'remote.server.org' on port 2200
## as user 'bob' from a Windows machine with PuTTY installed.
## Using the explicit special rshcmd = "<putty-plink>", will force
## makeClusterPSOCK() to search for and use the PuTTY plink software,
## preventing it from using other SSH clients on the system search PATH.
cl <- makeClusterPSOCK(
  "remote.server.org", user = "bob",
  rshcmd = "<putty-plink>",
  rshopts = c("-P", 2200, "-i", "C:/Users/bobby/.ssh/putty.ppk"),
  dryrun = TRUE
)


## EXAMPLE: Remote worker running on Linux from RStudio on Windows
## Connect to remote Unix machine 'remote.server.org' on port 2200
## as user 'bob' from a Windows machine via RStudio's SSH client.
## Using the explicit special rshcmd = "<rstudio-ssh>", will force
## makeClusterPSOCK() to use the SSH client that comes with RStudio,
## preventing it from using other SSH clients on the system search PATH.
cl <- makeClusterPSOCK(
  "remote.server.org", user = "bob", rshcmd = "<rstudio-ssh>",
  dryrun = TRUE
)
}
