Submitting batch jobs

Do you want 10,000 e-mails?

By default, condor will send you an e-mail message as each of your jobs completes. If you've submitted 10,000 jobs, that means 10,000 e-mails. This can clog the mail server, and make your life miserable.

Please place the following line in your condor submit file:

Notification    = Error

This means that condor will only send you an e-mail if there's an error while running the job.

Do you want to use up all your disk space?

At the end of most condor batch files, you'll see lines that look like this:

output   = mySimulation-$(Process).out
error    = mySimulation-$(Process).err
log      = mySimulation-$(Process).log

These lines define where the job's output, error, and log files are written. If you submit one job, the above lines are fine. If you submit 10,000 jobs, you'll create 30,000 files. If you submit mySimulation1, mySimulation2, ... you'll create an indefinite number of files. Sooner or later you'll fill up your home directory. Since you share the home directory on your server with everyone else in your working group, that means everyone in your group will be affected.

The general solution is to not write your output files into your home directory. Every workgroup server has a /data partition, which is normally several TB in size. It's a good idea to make sure your output files are written to this partition.

You can do this by:

• submitting your job from a directory on the /data partition;
• explicitly writing your output files to a directory on the /data partion; e.g.,

output   =  /a/data/<server>/<username>/mySimulation--$(Process).out
error    =  /a/data/<server>/<username>/mySimulation--$(Process).err
log      =  /a/data/<server>/<username>/mySimulation-$(Process).log

Don't forget to create /a/data/<server>/<username>/ before you submit your first job.

Use the vanilla environment

Unless you've specifically used the condor_compile command to compile your programs, you must submit your jobs in the "vanilla" universe. Any program that uses shared libraries cannot use condor_compile, and this includes most of the physics software at Nevis. Therefore, you are almost certainly required to have the following line in a command script:

universe = vanilla

Handling disk files

As you read through the User's Manual chapter on job submission, note that we use a shared file system at Nevis.

Because we use a shared file system at Nevis that's based on automount, it's a good idea to include the initialdir attribute in your command scripts. For example, when I submit a script that makes use of files in my directory /a/data/tanya/seligman/kit/TestArea/, I include the following line in my command script to make sure the executing machine has correctly mounted the directory:

initialdir = /a/data/tanya/seligman/kit/TestArea/ 

Important: Think about how you transfer your job's files

Picture this: You submit a condor batch procedure that runs thousands of jobs. Each one of those jobs reads and/or writes directly into a directory on your server, accessed via NFS. Let's say there are 200 batch queues in the Nevis condor system. That means that 200 jobs are trying to access the disk on your server at once.

Sounds like a recipe for disaster, doesn't it? You can crash your server by writing 200 files at once via NFS. It's happened several times at Nevis.

To solve this problem, don't rely on your job reading and writing files directly to a particular directory. Use commands like the following in your condor command file; look them up in the User's Manual:

should_transfer_files = YES
when_to_transfer_output = ON_EXIT
transfer_input_files = ...list of input files...

This will transfer your input files to the condor master server once, instead of 200 times; as your job is executing, it will write the output on a local area of the machine that's running the job. Once the job has finished executing, it will transfer the output file to the directory from which you submitted the job.

Result: you don't crash your server. You also don't clog up the network with unnecessary file transfers.

sh-style shells versus csh-style shells

We have discovered that the vanilla environment described in the Condor manual does not behave exactly as documented at Nevis. The following advice may be helpful:

There appears to be a difference in the way the sh and csh shells handle files in Condor. In sh, bash, or zsh (the default at Nevis) the examples in the Condor manual basically work as they are. In csh or tcsh, the scripts will fail due to "file not found" errors unless you do one of the following:

• Transfer all working files to the executing machine with the lines:

should_transfer_files = YES 
when_to_transfer_output = ON_EXIT 

• Include the full path name when you reference any file in your command script. For example, in my scripts, the following line fails:

executable = athena.csh

executable = /a/data/tanya/seligman/kit/TestArea/athena.csh

condor log files

If you want to see the condor daemons' log files for a machine with the name hostname, look in /a/data/<hostname>/condor/log. For example:

# ls -blrth /a/data/karthur/condor/log
-rw-r--r-- 1 condor condor  153 2010-04-13 15:07 StarterLog
-rw-r--r-- 1 condor condor 473K 2010-04-13 16:29 SchedLog
-rw-r--r-- 1 root   root   591K 2010-04-13 16:29 MasterLog
-rw-r--r-- 1 root   root   788K 2010-04-13 17:15 StartLog
-rw-r--r-- 1 root   root   562K 2010-04-13 17:25 NegotiatorLog
-rw-r--r-- 1 root   root   296K 2010-04-13 17:25 CollectorLog