An HTCondor pool is horizontally scalable to hundreds of thousands of execute cores and a similar number of jobs. HTCondor is also scalable down to run an entire pool on a single machine, and many scales between these two extremes.
HTCondor can be configured to use strong authentication and encryption between the services on remote machines used to manage jobs. The HTCondor worker node scratch directories can be encrypted, so that if a node is stolen or broken into, scratch files are unreadable.
- No Changes Necessary to User’s Source Code
No special programming is required to use HTCondor. HTCondor is able to run non-interactive programs.
- Pools of Machines can be Joined Together
Flocking is a feature of HTCondor that allows jobs submitted within a first pool of HTCondor machines to execute on a second pool. The mechanism is flexible, following requests from the job submission, while allowing the second pool, or a subset of machines within the second pool to set policies over the conditions under which jobs are executed.
- Jobs Can Be Ordered
The ordering of job execution required by dependencies among jobs in a set is easily handled. The set of jobs is specified using a directed acyclic graph, where each job is a node in the graph. Jobs are submitted to HTCondor following the dependencies given by the graph.
- HTCondor Can Use Remote Resources, from a Grid, or a Cloud, or a Supercomputer Allocation
The technique of glidein allows jobs submitted to HTCondor to be executed on grid machines in various locations worldwide. HTCondor’s grid universe allows direct submission of jobs to remote systems.
- Sensitive to the Desires of Machine Owners
The owner of a machine has complete priority over the use of the machine. An owner is generally happy to let others compute on the machine while it is idle, but wants it back promptly upon returning. The owner does not want to take special action to regain control. HTCondor handles this automatically.
- Flexible Policy Mechanisms
HTCondor allows users to specify very flexible policies for how they want jobs to be run. Conversely, it independently allows the owners of machines to specify very flexible policies about what jobs (if any) should be run on their machines. Together HTCondor merges and adjudicates these policy requests into one coherent system.
The ClassAd mechanism in HTCondor provides an expressive framework for matchmaking resource requests with resource offers. Users can easily request both job requirements and job desires. For example, a user can require that a for a job to run at all, it must be started on a machine with a certain amount of memory, but should there be multiple available machines that meet that criteria, to select the one with the most memory.