Swift Configuration Simplified
==============================


The swift configuration file (swift.conf) is a description of how swift should execute your
swift workflow on one or more of your target computation resources. The swift config file
therefore contains three aspects:

- A description of the target resource, and what you want from it, such as:
    * URL of the site, scheduler the system uses, what queue you want to run on, how many nodes you need, etc

- A description of application that you will run on these resources:
    * Executable for each app, walltimes for apps etc

- Configuration for the workflow execution behavior:
    * handling errors, network port to use, leave files for debug etc.

Simple canned configurations work great for a vast majority of cases. Nevertheless, Swift provides
the user with several different paramenters to tune and tweak your workflow to perfection.

Here's the skeleton of a swift.conf:

[source,python]
----
site.<name> {
    # How to negotiate resources with the site
    execution {
        [URL        : < URL_OF_COMPUTE_RESOURCE > ]
        type        : < local | coaster | coaster-persistent >
        [jobmanager : < <local|ssh-cl>:<local,pbs,sge,slurm..>  >]
    }

    # Directory for placing intermediate work files
    workDirectory: <path>

    # Site specific options (eg. queue to use,nodes to request)
    [<site options>]

    # How to move data to/from the compute nodes
    [staging: "swift" | "local" | "service-local" | "shared-fs" | "wrapper"]

    # Describe the application to run on this site
    [<application declarations>]
}
----

Here's a simple config file for a cluster which uses slurm scheduler:
[source, python]
-----
sites : midway

site.midway {
    execution {
        type      : "coaster"                         # Use coasters to run on remote sites
        URL       : "swift.rcc.uchicago.edu"          # Midway login node | Alternatively use midway.rcc.uchicago.edu
        jobManager: "ssh-cl:slurm"                    # Use ssh-cl to connect, slurm is the Local resource manager
        options {
            jobQueue        : "sandyb"                # Select queue from (sandyb, westmere, ...)
        }
    }
    staging             : "local"                     # Stage files from "local" system to Midway
    workDirectory       : "/tmp/"${env.MIDWAY_USERNAME} # Location for intermediate files
    maxParallelTasks    : 101                         # Maximum number of parallel tasks
    initialParallelTasks: 100                         # Maximum number of tasks at start
    app.ALL { executable: "*" }                       # All tasks to be found from commandline
}
-----