Client Configuration

In this section, we assume that you already have installed the Gurobi Optimizer package on your client machine. After this, you will need to understand the role of the client license file and how grbcluster can help in generating it. Finally, we will review the load balancing and priority management that can be controlled with some of the configuration properties.

Client License File

A client program needs to be told how to reach a Remote Services cluster. There are generally two ways to do this. The first is through the programming language APIs. We’ll discuss this option in a later section on programming with Remote Services. The second is through a license file. You can create a client license file yourself or edit an existing one, using your favorite text editor (Notepad is a good choice on Windows). The license file should be named gurobi.lic.

The license file contains a list of properties of the form PROPERTY=value. Lines that begin with the # symbol are treated as comments and are ignored. The license file must be placed in one of the following locations:

  • C:\gurobi\ on Windows

  • /opt/gurobi/ on Linux

  • /Library/gurobi/ on macOS

  • The user’s home directory

You can also set the environment variable GRB_LICENSE_FILE to point to this file.

Connecting to a Cluster Manager

Here are the properties you can set to connect to a Cluster Manager:

CSMANAGER

The URL of the Cluster Manager, including the protocol scheme and port. For example, use http://mymanager:61080 to access a Cluster Manager using HTTP on port 61080, or https://mymanager:61443 to access a cluster over HTTPS on port 61443.

CSAPIACCESSID

A unique identifier used to authenticate an application on a cluster.

CSAPISECRET

The secret password associated with an API access ID.

USERNAME

The username to access the cluster.

PASSWORD

The client password to access the cluster.

CSAUTHTOKEN

Used internally to store the JWT authentication token.

These don’t all need to be set - you just set the properties that are relevant for the authentication method you are using. If the license file specifies several authentication methods to a Cluster Manager, the following precedence order applies:

  • API key defined with CSAPIACCESSID and CSAPISECRET

  • JWT authentication token with CSAUTHTOKEN

  • Username and password with USERNAME and PASSWORD

Connecting to a Cluster Node

Here are the properties you can set to connect to a cluster node in a self-managed cluster:

COMPUTESERVER

The fully qualified name of the main node used to access the cluster, plus the protocol scheme and port (if needed). For example, you can just use server1 to access a cluster using HTTP on the default port, or https://server1:61000 to access a cluster over HTTPS using port 61000. You can also specify a comma-separated list of names so that other nodes can be used in case the first node can’t be reached.

ROUTER

The router URL (if you are using a router).

PASSWORD

The client password to access the cluster. Note that clients must provide the original password (not hashed) and it will be exchanged encrypted if HTTPS is used.

Other Properties

You can also specify additional properties that affect job processing (whether you use a Cluster Manager or not):

CSAPPNAME

Application name. Once defined, the application name will be assigned to all jobs and batches created so that you can better track the activity of the cluster by application.

PRIORITY

Job Priority. Higher priority jobs take precedence over lower priority jobs.

GROUP

Job group. If your cluster has been set up with groups, you can specify the group to submit the job to. The job will only be executed on nodes that are members of this group if specified. The value of this property can also be a list of groups, and you can also specify a priority for each group. For example: group1:10,group2:50

QUEUETIMEOUT

Queuing timeout (in seconds). A job that has been sitting in the queue for longer than the specified QUEUETIMEOUT value will return with a JOB_REJECTED error.

IDLETIMEOUT

Idle job timeout (in seconds). This property allows you to set a limit on how long a Compute Server job can sit idle before the server kills the job.

Examples

Here is an example of a client license file that would allow a client to connect to a Cluster Manager with an API key, and submit all the jobs under a specific application name:

CSMANAGER=http://mymanager:61080
CSAPIACCESSID=0e8c35d5-ff20-4e5d-a639-10105e56b264
CSAPISECRET=d588f010-ad47-4310-933e-1902057661c9
CSAPPNAME=app1

Here is another example that would allow you to connect a self-managed Compute Server with a specific password, and submit all the jobs with priority 10:

COMPUTESERVER=http://server1:61000
PASSWORD=abcd
PRIORITY=10

The gurobi_cl or grbcluster tools provide command-line flags that allow you to set most of these properties. These tools will read the license file, but values specified via these command-line flags will override any values provided in the license file.

Generating a Client License with grbcluster

Your primary tool for issuing cluster commands is a command-line program called grbcluster. The format of the command-line tool is as follows (see the reference section for more information):

grbcluster --help                Display usage
grbcluster command [flags]       Execute a top-level command
grbcluster command --help        Display help about a top-level command
grbcluster group command [flags] Execute a command from a group
grbcluster group command --help  Display help about a command
                                 from a group

The first important command is the login command, which accepts various flags to allow you to configure your connection. Once your connection is validated, it will save these parameters into the license file. If the license file does not exist, it will create one. If you want to store the license file in a custom location, you can use the environment variable GRB_LICENSE_FILE. The command tools grbcluster, gurobi_cl, and grbtune will first read the client license file so that you do not need to specify connection parameters each time.

Here are some examples of the login command :

  • Log in to a Cluster Manager with a username and password:

    grbcluster login --manager=http://mymanager:61080 --username=gurobi

    Note that if a password is necessary, you will be prompted for it. This is more secure than providing one on the command line, but that is an option too (using the —-password flag).

  • Refresh login to a Cluster Manager to extend an expired session:

    grbcluster login

  • Log in to a Cluster Manager with an API key:

    grbcluster login --manager=http://mymanager:61080 --access=... --secret=...

  • Log in to a Compute Server in a self-managed cluster:

    grbcluster login --server=http://server1:61000

  • Log in to a Compute Server that uses a router:

    grbcluster login --server=http://server1:61001 --router=http://myrouter:61000

Queueing, Load Balancing, and Job Priorities

As noted earlier, Gurobi Compute Servers support job priorities. You can assign an integer priority between -100 and 100 to each job (the default is 0). When choosing among queued jobs, the Compute Server will run the highest priority job first. Note that servers will never preempt running jobs. You can set the priority in the client license file, or using the PRIORITY parameter in the programming language APIs.

We have chosen to give priority 100 a special meaning. A priority 100 job will start immediately, even if this means that a server will exceed its job limit. You should be cautious with priority 100 jobs, since submitting too many at once could lead to very high server loads, which could lead to poor performance and even crashes in extreme cases. Note that this feature must be enabled by the system administrator using the HARDJOBLIMIT configuration property.

With the Remote Services grouping feature, the system administrator may have assigned groups to the cluster nodes. This can be quite useful when some nodes in the cluster are different from others. For example, some nodes may have more memory or faster CPUs. Using this feature, you can force jobs to only run on the appropriate type of machines. If all nodes of the requested group are at capacity, jobs will be queued until a member of that group is available.

You can submit an optimization job to a given group by using the GROUP property of the client license file. You can also set the CSGROUP parameter in the programming interface.

You can use this parameter to target a single group or a list of groups, and you can specify a priority for each group. Here is an example that shows how you would use this parameter to submit a job to group1 with priority 10 and to group2 with priority 50.

group1:10,group2:50

Note that if no group specified for the submitted job, the job can run on any node.