# condor_findhost¶

find machine(s) in the pool that can be used with minimal impact on currently running HTCondor jobs and best meet any specified constraints

## Synopsis¶

condor_findhost [-help ] [-m ] [-n num] [-c c_expr] [-r r_expr] [-p centralmanagerhostname]

## Description¶

condor_findhost searches an HTCondor pool of machines for the best machine or machines that will have the minimum impact on running HTCondor jobs if the machine or machines are taken out of the pool. The search may be limited to the machine or machines that match a set of constraints and rank expression.

condor_findhost returns a fully-qualified domain name for each machine. The search is limited (constrained) to a specific set of machines using the -c option. The search can use the -r option for rank, the criterion used for selecting a machine or machines from the constrained list.

## Options¶

-help
Display usage information and exit
-m
Only search for entire machines. Slots within an entire machine are not considered.
-n num
Find and list up to num machines that fulfill the specification. num is an integer greater than zero.
-c c_expr
Constrain the search to only consider machines that result from the evaluation of c_expr. c_expr is a ClassAd expression.
-r r_expr
r_expr is the rank expression evaluated to use as a basis for machine selection. r_expr is a ClassAd expression.
-p centralmanagerhostname
Specify the pool to be searched by giving the central manager’s host name. Without this option, the current pool is searched.

## General Remarks¶

condor_findhost is used to locate a machine within a pool that can be taken out of the pool with the least disturbance of the pool.

An administrator should set preemption requirements for the HTCondor pool. The expression

(Interactive =?= TRUE )


will let condor_findhost know that it can claim a machine even if HTCondor would not normally preempt a job running on that machine.

## Exit Status¶

The exit status of condor_findhost is zero on success. If not able to identify as many machines as requested, it returns one more than the number of machines identified. For example, if 8 machines are requested, and condor_findhost only locates 6, the exit status will be 7. If not able to locate any machines, or an error is encountered, condor_findhost will return the value 1.

## Examples¶

To find and list four machines, preferring those with the highest mips (on Drystone benchmark) rating:

condor_findhost -n 4 -r "mips"


To find and list 24 machines, considering only those where the kflops attribute is not defined:

condor_findhost -n 24 -c "kflops=?=undefined"