qsub

qsub provides the qsub_lapply function, which helps you parallellise lapply calls to gridengine clusters.

Usage

After installation and configuration of the qsub package, running a job on a cluster supporting gridengine is as easy as:

library(qsub)
qsub_lapply(1:3, function(i) i + 1)

## [[1]]
## [1] 2
## 
## [[2]]
## [1] 3
## 
## [[3]]
## [1] 4

Permanent configuration

If the previous section worked just fine, you can for a permanent configuration of the qsub config as follows:

set_default_qsub_config(qsub_config, permanent = TRUE)

Installation

On unix-based systems, you will first have to install libssh.

• deb: apt-get install libssh-dev (Debian, Ubuntu, etc)
• rpm: dnf install libssh-devel (Fedora, EPEL) (if dnf is not install, try yum)
• brew: brew install libssh (OSX)

You can install qsub with devtools as follows:

devtools::install_github("rcannood/qsub")

Initial test

For the remainder of this README, we will assume you have an account called myuser on a cluster located at mycluster.address.org listening on port 1234. This cluster is henceforth called the ‘remote’. You will require a local folder to store temporary data in (e.g. /tmp/r2gridengine), and a remote folder to store temporary data in (e.g. /scratch/personal/myuser/r2gridengine).

After installation of the qsub package, first try out whether you can connect to the remote. If you have not yet set up an SSH key and uploaded it to the remote, you will be asked for password.

qsub_config <- create_qsub_config(
  remote = "[email protected]:1234",
  local_tmp_path = "/tmp/r2gridengine",
  remote_tmp_path = "/scratch/personal/myuser/r2gridengine"
)

qsub_lapply(1:3, function(i) i + 1, qsub_config = qsub_config) 

Setting up an SSH key

If you regularly submit jobs to the remote, it will be extremely useful to set up an SSH key configuration. This way, you don’t need to enter your password every time you execute qsub_lapply.

On Windows, you will first need to install Git bash or use the Linux for Windows Subsystem.

The first step will be to open bash and create a file which contains the following content, and save it to .ssh/config.

Host myhost
  HostName mycluster.address.org
  Port 1234
  User myuser

Secondly, generate an SSH key. You don’t need to enter a password. If you do, though, you will be asked for this password every time you use your SSH key.

ssh-keygen -t rsa

Finally, copy the public key (id_rsa.pub) to the remote. Never share your private key (id_rsa)!

ssh-copy-id myhost

Alternatively, if you do not have ssh-copy-id installed, you can run the following:

cat ~/.ssh/id_rsa.pub | ssh myhost "mkdir -p ~/.ssh && chmod 700 ~/.ssh && cat >>  ~/.ssh/authorized_keys"

Customisation of individual runs

Some tasks will require you to finetune the qsub config, for example because they require more walltime or memory than allowed by default. These can also be specified using the create_qsub_config command, or using override_qsub_config if you have already created a default qsub config. Check ?override_qsub_config for a detailed explanation of each of the possible parameters.

qsub_lapply(
  X = 1:3,
  FUN = function(i) {
    # simulate a very long calculation time
    # this might annoy other users of the cluster, 
    # but sometimes there is no way around it
    Sys.sleep(sample.int(3600, 1))
    i + 1
  },
  qsub_config = override_qsub_config(
    name = "MyJob", # this name will show up in qstat
    mc_cores = 2, # the number of cores to allocate per element in X
    memory = "10G", # memory per core per task
    max_wall_time = "12:00:00" # allow each task to run for 12h
  )
)

Asynchronous jobs

In almost every case, it is most practical to run jobs asynchronously. This allows you to start up a job, save the meta data, come back later, and fetch the results from the cluster. This can be done by changing the wait parameter.

qsub_async <- qsub_lapply(
  X = 1:3,
  FUN = function(i) {
    Sys.sleep(10)
    i + 1
  },
  qsub_config = override_qsub_config(
    wait = FALSE
  )
)

readr::write_rds(qsub_async, "temp_file.rds")

# you can restart your computer / R session after having saved the `qsub_async` object somewhere.
qsub_async <- readr::read_rds("temp_file.rds")

# if the job has finished running, this will retrieve the output
qsub_retrieve(qsub_async)

Specify which objects gets transferred

By default, qsub_lapply will transfer all objects in your current environment to the cluster. This might result in long waiting times if the current environment is very large. You can define which objects get transferred to the cluster as follows:

j <- 1
k <- rep(10, 1000000000) # 7.5 Gb
qsub_lapply(
  X = 1:3,
  FUN = function(i) {
    i + j
  },
  qsub_environment = "j"
)

Oh no, something went wrong

Inevitably, something will go break. qsub will try to help you by reading out the log files if no output was produced.

qsub_lapply(
  X = 1:3,
  FUN = function(i) {
    if (i == 2) stop("Something went wrong!")
    i + 1
  }
)

## Error in FUN(X[[i]], ...): File: /home/rcannood/Workspace/.r2gridengine/20190213_133822_r2qsub_4XGIFwJTDg/log/log.2.e.txt
## Error in (function (i)  : Something went wrong!
## Calls: lapply -> FUN -> do.call -> <Anonymous>
## Execution halted

Alternatively, you might anticipate possible errors but still be interested in the rest of the output. In this case, the error will be returned as an attribute.

qsub_lapply(
  X = 1:3,
  FUN = function(i) {
    if (i == 2) stop("Something went wrong!")
    i + 1
  },
  qsub_config = override_qsub_config(
    stop_on_error = FALSE
  )
)

## [[1]]
## [1] 2
## 
## [[2]]
## [1] NA
## attr(,"qsub_error")
## [1] "File: /home/rcannood/Workspace/.r2gridengine/20190213_133830_r2qsub_I4Tk4mjacf/log/log.2.e.txt\nError in (function (i)  : Something went wrong!\nCalls: lapply -> FUN -> do.call -> <Anonymous>\nExecution halted\n"
## 
## [[3]]
## [1] 4

If all help prevails, you can try to manually debug the session by not removing the temporary files at the end of an execution by setting remove_tmp_folder to FALSE, logging into the remote server, going to the temporary folder located at get_default_qsub_config()$remote_tmp_path, and executing script.R line by line in R, by hand.

qsub_lapply(
  X = 1:3,
  FUN = function(i) {
    if (i == 2) stop("Something went wrong!")
    i + 1
  },
  qsub_config = override_qsub_config(
    remove_tmp_folder = FALSE
  )
)

Latest changes

Check out news(package = "qsub") or NEWS.md for a full list of changes.

Latest changes in qsub 1.1.0 (13-02-2019)

• MINOR CHANGE: There is now an option to compress the output files, which is turned on by default.

• MINOR CHANGE: Allow unix systems to use rsync instead of cp for fetching the qsub output.

• BUG FIX: Fix qsub_retrieve() when processing the output; it did not take into account that batch_tasks could not be equal to 1.

• MINOR CHANGE: qsub_retrieve() now uses pbapply when loading in the output.

• BUG FIX: Test ssh connection pointer before using it.

• BUG FIX: Do not remove the first line of an error file.

• MINOR CHANGE: Use absolute paths to output standard output and error logs (#16, suggested by @mmehan).

• MINOR CHANGE; Allow rsync to also use the username@host:port notation (#16, suggested by @mmehan).

Latest changes in qsub 1.0.0 (30-07-2018)

• INITIAL RELEASE: qsub allows you to run lapply() calls in parallel by submitting them to gridengine clusters using the qsub command.