Stain

Stain (Slurm Container) is an R package that generates "containers" for slurm jobs. NOTE: still in beta!

Installation

devtools::install_github("jmousseau/Stain")

SSH Setup

If slurm jobs are run on a remote host, setup a public/private ssh key to allow remote slurm job submissions. To automatically generate the bash code required to do so, see ?stain_ssh_setup. The documentation contains directions to set up ssh keys for the remote host.

---

Getting Started

As an example, pretend the following files are used in a slurm job to convert a tab delimited file to a CSV file.

# main.R

main <- function() {
    # The reason why the "./data" directory was used will be clear later.
    input_file <- paste("./data", input_file_name, sep = "/")
    data <- data.table::fread(input_file)
    default_write(data, output_file_name)
}

# default_write.R

default_write <- function(data, file) {
    write.csv(data, file, row.names = FALSE)
}

# data.txt - A space delimited data file.

A Stain object is used to manage a slurm container. Its initializer takes a directory and a list of options. If the directory is an existing slurm container, the container will be loaded. Otherwise, a new slurm container will be created. For more on what is inside a slurm container, see Slurm Container Details.

sbatch_opts is a list of functions that take a string parameter representing the value and returns that value as a formatted key-value pair. sbatch_mail_type_opts is a list of all sbatch mail types. One may choose to pass a custom option using the form "--<key>=<value>".

# Create a new slurm container in the current working directory.
stain <- Stain$new(name = "stain-example", options = c(
    sbatch_opts$memory("16g"),
    sbatch_opts$mail_user("[email protected]"),
    sbatch_mail_type_opts$all
))

# Configure the remote host where the slurm job will be submitted.
stain$set_remote_host("<user>", "<host>")

# Add any R source files used by the slurm job.
stain$add_sources(c("main.R", "default_write.R"))

# Add any data files.
stain$add_data("data.txt")

The add_data function will place all data files in a ./data directory which only exists when a slurm job is running. NOTE: Files added will not retain their parent directory structure.

One of the source files in a slurm container must contain a main() function. Once an R source file containing a main() function has been added, one should see a message similar to:

2 globals to specify:

    - input_file_name
    - output_file_name

Set these globals in the `globals` property of your Stain instance.

The globals are variables that not defined anywhere in the source files but used in main(). But why would any variable not have a value? In the example, input_file_name and output_file_name are undefined. This means they may be edited using a Stain object, rather than explicitly hard coded in a source file.

# Assigning globals.
stain$globals$input_file_name <- "data.txt"
stain$globals$output_file_name <- "converted_data.csv"

# Submit to <user>@<host>:<submit directory> where the <submit directory> is
# ~/stain by default.
stain$submit()

# Jobs can be canceled.
stain$cancel(job_ids = c("<job_id>"))

# When a slurm job has finished, the output files may be fetched.
stain$fetch_output()

# View a history of job submissions.
stain$submission_history()

Now image a case where one would like to run these same scripts on a different file. Remember how input_file_name and output_file_name where left accessible by our slurm container? The code below will configure the container for a new input file.

# "stain-example" is the directory specified previously by the "name" parameter
# which now represents a directory of an existing slurm container.
stain <- Stain$new("stain-example")

# Add the new data file.
stain$add_data("data_2.txt")

# Change the globals.
stain$globals$input_file_name <- "data_2.txt"
stain$globals$output_file_name <- "converted_data_2.csv"

stain$submit()

In most cases submitting all variants of a job then copying back all the output is the most logical because the fetch_output will always copy all the output even if some of the files have already been copied.

---

Dependency Submissions

It is often desirable for one job to submit after a previous job has finished. Stain makes this easy by allowing you to specify a dependency list using the PREVIOUS(<n>|ALL) placeholder.

# When submitting, use the placeholder to refer to n previous jobs. In this case
# the job will only start when the previous 2 jobs have finished with an exit
# code of 0.
stain$submit(dependency_list = "afterok:PREVIOUS(2)")

# To refer to all previous jobs for the Stain, user PREVIOUS(ALL).
stain$submit(dependency_list = "afterok:PREVIOUS(ALL)")

"afterok" is one of many possible labels in the dependency list. The sbatch docs go into more detail about the different "--dependency" flag options.

---

Logs

Stain will automatically store the log output of each submission in a separate log file. The log file is specified by a unique identifier assigned during submission.

# Fetch all log files from the remote host.
stain$fetch_logs()

# The submission history will contain a column named "log_id".
stain$submission_history()

# Read the contents of a specific log file.
contents <- stain$get_log("<log id>")

---

Slurm Container Details

A slurm container is simply a directory structure to organize components required for a slurm job. The components are stored in the .stain/ directory. Here is a breakdown of the .stain/ subdirectories.

• data/ Any data files specified in a Stain object will be copied here. Copied data files will not retain there parent directory structure. Data is available in the ./data directory when the slurm job is running.

• objects/ Any globals set in a Stain object will be written here as <name>.RData where <name> is the name of the global. These object files will be loaded prior to executing any R code.

• sources/ Any R source files specified in a Stain object will be copied here. One of the source files must contain a main() function. Also contains .default_stain_main.R which executes the R code.

• logs/ A log file with a unique identifier and path will be stored here for each submission. Log ids are list in the Stain object submission_history() method.

• meta.json A JSON file that stores metadata about the Stain. Information includes things like previously used sbatch options, for when someone loads an existing Stain and expects the options when submitting to be the same as those specified during initialization, and submission history.

The files in sources/ and data/ may be listed using the list_files() Stain method.

Another core component of a slurm container is the submit.slurm bash script which is configured for the specified sbatch options and exists at the top level of a slurm container.