Conventions

3.5 Credential Overview

Moab supports the concept of credentials, which provide a means of attributing policy and resource access to entities such as users and groups. These credentials allow specification of job ownership, tracking of resource usage, enforcement of policies, and many other features. There are five types of credentials -user, group, account, class, and QoS. While the credentials have many similarities, each plays a slightly different role.

• General Credential Attributes
• User Credential
• Group Credential
• Account (or Project) Credential
• Class (or Queue) Credential
• QoS Credential

3.5-A General Credential Attributes

Internally, credentials are maintained as objects. Credentials can be created, destroyed, queried, and modified. They are associated with jobs and requests providing access and privileges. Each credential type has the following attributes:

• Priority Settings
• Usage Limits
• Service Targets
• Credential and Partition Access
• Statistics
• Credential Defaults, State and Configuration Information

All credentials represent a form of identity, and when applied to a job, express ownership. Consequently, jobs are subject to policies and limits associated with their owners.

Credential Priority Settings

Each credential may be assigned a priority using the PRIORITY attribute. This priority affects a job's total credential priority factor as described in the Priority Factors section. In addition, each credential may also specify priority weight offsets, which adjust priority weights that apply to associated jobs. These priority weight offsets include FSWEIGHT (See Priority-Based Fairshare for more information.), QTWEIGHT, and XFWEIGHT.

For example:

# set priority weights
CREDWEIGHT      1
USERWEIGHT      1
CLASSWEIGHT     1
SERVICEWEIGHT   1
XFACTORWEIGHT   10
QUEUETIMEWEIGHT 1000
# set credential priorities
USERCFG[john] PRIORITY=200
CLASSCFG[batch] PRIORITY=15
CLASSCFG[debug] PRIORITY=100
QOSCFG[bottomfeeder] QTWEIGHT=-50 XFWEIGHT=100
ACCOUNTCFG[topfeeder] PRIORITY=100

Credential Usage Limits

Usage limits constrain which jobs may run, which jobs may be considered for scheduling, and what quantity of resources each individual job may consume. With usage limits, policies such as MAXJOB, MAXNODE, and MAXMEM may be enforced against both idle and active jobs. Limits may be applied in any combination as shown in the example below where usage limits include 32 active processors per group and 12 active jobs for user john. For a job to run, it must satisfy the most limiting policies of all associated credentials. The Throttling Policy section documents credential usage limits in detail.

GROUPCFG[DEFAULT] MAXPROC=32 MAXNODE=100
GROUPCFG[staff]   MAXNODE=200
USERCFG[john]     MAXJOB=12

Service Targets

Credential service targets allow jobs to obtain special treatment to meet usage or response time based metrics. Additional information about service targets can be found in the Fairshare section.

Credential and Partition Access

Access to partitions and to other credentials may be specified on a per credential basis with credential access lists, default credentials, and credential membership lists.

Credential Access Lists

You can use the ALIST, PLIST, and QLIST attributes (shown in the following table) to specify the list of credentials or partitions that a given credential may access.

Example 3-1:  

USERCFG[bob]   ALIST=jupiter,quantum
USERCFG[steve] ALIST=quantum

Account-based access lists are only enforced if using an allocation manager or if the ENFORCEACCOUNTACCESS parameter is set to "TRUE."

Assigning Default Credentials

Use the *DEF attribute (shown in the following table) to specify the default credential or partition for a particular credential.

Example 3-2:  

# user bob can access accounts a2, a3, and a6. If no account is explicitly requested, 
# his job will be assigned to account a3
USERCFG[bob]   ALIST=a2,a3,a6 ADEF=a3 
# user steve can access accounts a14, a7, a2, a6, and a1. If no account is explicitly 
# requested, his job will be assigned to account a2
USERCFG[steve] ALIST=a14,a7,a2,a6,a1 ADEF=a2

Specifying Credential Membership Lists

As an alternate to specifying access lists, administrators may also specify membership lists. This allows a credential to specify who can access it rather than allowing each credential to specify which credentials it can access. Membership lists are controlled using the MEMBERULIST, EXCLUDEUSERLIST and REQUIREDUSERLIST attributes, shown in the following table:

Example 3-3:  

# account omega3 can only be accessed by users johnh, stevek, jenp
ACCOUNTCFG[omega3] MEMBERULIST=johnh,stevek,jenp

Example 3-4: Controlling Partition Access on a Per User Basis

A site may specify the user john may access partitions atlas, pluto, and zeus and will default to partition pluto. To do this, include the following line in the configuration file:

USERCFG[john] PLIST=atlas,pluto,zeus

Example 3-5: Controlling QoS Access on a Per Group Basis

A site may also choose to allow everyone in the group staff to access QoS standard and special with a default QoS of standard. To do this, include the following line in the configuration file:

GROUPCFG[staff] QLIST=standard,special QDEF=standard

Example 3-6: Controlling Resource Access on a Per Account Basis

An organization wants to allow everyone in the account omega3 to access nodes 20 through 24. To do this, include the following in the configuration file:

ACCOUNTCFG[omega3] MEMBERULIST=johnh,stevek,jenp
SRCFG[omega3]   HOSTLIST=r:20-24 ACCOUNTLIST=omega3

Credential Statistics

Full statistics are maintained for each credential instance. These statistics record current and historical resource usage, level of service delivered, accuracy of requests, and many other aspects of workload. Note, though, that you must explicitly enable credential statistics as they are not tracked by default. You can enable credential statistics by including the following in the configuration file:

USERCFG[DEFAULT]        ENABLEPROFILING=TRUE
GROUPCFG[DEFAULT]       ENABLEPROFILING=TRUE
ACCOUNTCFG[DEFAULT]     ENABLEPROFILING=TRUE
CLASSCFG[DEFAULT]       ENABLEPROFILING=TRUE
QOSCFG[DEFAULT]         ENABLEPROFILING=TRUE

Job Defaults, Credential State, and General Configuration

Credentials may apply defaults and force job configuration settings via the following parameters:

USERCFG[steve] COMMENT='works for boss, provides good service'
CLASSCFG[i3]   COMMENT='queue for I/O intensive workload'

HOLD
Description	Specifies a hold should be placed on all jobs associated with the target credential. The order in which this HOLD attribute is evaluated depends on the following credential precedence: USERCFG, GROUPCFG, ACCOUNTCFG, CLASSCFG, QOSCFG, USERCFG[DEFAULT], GROUPCFG[DEFAULT], ACCOUNTCFG[DEFAULT], CLASSCFG[DEFAULT], QOSCFG[DEFAULT].
Example	GROUPCFG[bert] HOLD=yes

CLASSCFG[batch] JOBFLAGS=suspendable
QOSCFG[special] JOBFLAGS=restartable

ACCOUNTCFG[general]  NOSUBMIT=TRUE
CLASSCFG[special]    NOSUBMIT=TRUE

CLASSCFG[bigmem] OVERRUN=00:15:00

GROUPCFG[staff] VARIABLE='nocharge=true'

Credentials may carry additional configuration information. They may specify that detailed statistical profiling should occur, that submitted jobs should be held, or that corresponding jobs should be marked as preemptible.

3.5-B User Credential

The user credential is the fundamental credential within a workload manager; each job requires an association with exactly one user. In fact, the user credential is the only required credential in Moab; all others are optional. In most cases, the job's user credential is configured within or managed by the operating system itself, although Moab may be configured to obtain this information from an independent security and identity management service.

As the fundamental credential, the user credential has a number of unique attributes.

• Role
• Email Address
• Disable Moab User Email

Role

Moab supports role-based authorization, mapping particular roles to collections of specific users. See the Security section for more information.

Email Address

Facilities exist to allow user notification in the event of job or system failures or under other general conditions. This attribute allows these notifications to be mailed directly to the target user.

USERCFG[sally]    [email protected]

Disable Moab User Email

You can disable Moab email notifications for a specific user.

USERCFG[john]    NOEMAIL=TRUE

3.5-C Group Credential

The group credential represents an aggregation of users. User-to-group mappings are often specified by the operating system or resource manager and typically map to a user's UNIX group ID. However, user-to-group mappings may also be provided by a security and identity management service, or you can specify such directly within Moab.

With many resource managers such as TORQUE, PBSPro, and LSF, the group associated with a job is either the user's active primary group as specified within the operating system or a group that is explicitly requested at job submission time. When a secondary group is requested, the user's default group and associated policies are not taken into account. Also note that a job may only run under one group. If more constraining policies are required for these systems, an alternate aggregation scheme such as the use of Account or QoS credentials is recommended.

To submit a job as a secondary group, refer to your local resource manager's job submission options. For TORQUE users, see the group_list=g_list option of the qsub -W command.

3.5-D Account Credential

The account credential is also referred to as the project. This credential is generally associated with a group of users along the lines of a particular project for accounting and billing purposes. User-to-accounting mapping may be obtained from a resource manager or allocation manager, or you can configure it directly within Moab. Access to an account can be controlled via the ALIST and ADEF credential attributes specified via the Identity Manager or the moab.cfg file.

The MANAGERS attribute (applicable only to the account and class credentials) allows an administrator to assign a user the ability to manage jobs inside the credential, as if the user is the job owner.

Example 3-7: MANAGERS Attribute

ACCOUNTCFG[general]  MANAGERS=ops
ACCOUNTCFG[special]  MANAGERS=stevep

If a user is able to access more than one account, the desired account can be specified at job submission time using the resource-manager specific attribute. For example, with TORQUE this is accomplished using the -A argument to the qsub command.

Example 3-8: Enforcing Account Usage

Job-to-account mapping can be enforced using the ALIST attribute and the ENFORCEACCOUNTACCESS parameter.

USERCFG[john]    ALIST=proj1,proj3
USERCFG[steve]   ALIST=proj2,proj3,proj4
USERCFG[brad]    ALIST=proj1
USERCFG[DEFAULT] ALIST=proj2
ENFORCEACCOUNTACCESS TRUE
...

3.5-E Class Credential

• Class Job Defaults
• Per Job Min/Max Limits
• Resource Access
• Class Membership Constraints
• Attributes Enabling Class Access to Other Credentials
• Special Class Attributes (such as Managers and Job Prologs)
• Setting Default Classes
• Creating a Remap Class
• Class Attribute Overview
• Enabling Queue Complex Functionality

The concept of the class credential is derived from the resource manager class or queue object. Classes differ from other credentials in that they more directly impact job attributes. In standard HPC usage, a user submits a job to a class and this class imposes a number of factors on the job. The attributes of a class may be specified within the resource manager or directly within Moab. Class attributes include the following:

• Job Defaults
• Per Job Min/Max Limits
• Resource Access Constraints
• Class Membership Constraints
• Attributes Enabling Class Access to Other Credentials
• Special Class Attributes

When using SLURM, Moab classes have a one-to-one relationship with SLURM partitions of the same name.

For all classes configured in Moab, a resource manager queue with the same name should be created.

When TORQUE reports a new queue to Moab a class of the same name is automatically applied to all nodes.

Class Job Defaults

Classes can be assigned to a default job template that can apply values to job attributes not explicitly specified by the submitter. Additionally, you can specify shortcut attributes from the table that follows:

Defaults set in a class/queue of the resource manager will override the default values of the corresponding class/queue specified in Moab.

RESOURCELIMITPOLICY must be configured in order for the CLASSCFG limits to take effect.

Example 3-9:  

CLASSCFG[batch] DEFAULT.DISK=200MB DEFAULT.FEATURES=prod DEFAULT.WCLIMIT=1:00:00
CLASSCFG[debug] DEFAULT.FEATURES=debug DEFAULT.WCLIMIT=00:05:00

Per Job Min/Max Limits

Classes can be assigned a minimum and a maximum job template that constrains resource requests. Jobs submitted to a particular queue must meet the resource request constraints of these templates. If a job submission exceeds these limits, the entire job submit fails.

The parameters listed in the preceding table are for classes only, and they function on a per-job basis. The MAX.* and MIN.* parameters are different from the MAXJOB, MAXNODE, and MAXMEM parameters described earlier in Credential Usage Limits.

Resource Access

Classes may be associated with a particular set of compute resources. Consequently, jobs submitted to a given class may only use listed resources. This may be handled at the resource manager level or via the CLASSCFG HOSTLIST attribute.

Class Membership Constraints

Classes may be configured at either the resource manager or scheduler level to only allow select users and groups to access them. Jobs that do not meet these criteria are rejected. If specifying class membership/access at the resource manager level, see the respective resource manager documentation. Moab automatically detects and enforces these constraints. If specifying class membership/access at the scheduler level, use the REQUIREDUSERLIST or EXCLUDEUSERLIST attributes of the CLASSCFG parameter.

Under most resource managers, jobs must always be a member of one and only one class.

Attributes Enabling Class Access to Other Credentials

Classes may be configured to allow jobs to access other credentials such as QoSes and Accounts. This is accomplished using the QDEF, QLIST, ADEF, and ALIST attributes.

Special Class Attributes

The class object also possesses a few unique attributes including JOBPROLOG, JOBEPILOG, RESFAILPOLICY, and DISABLEAM attributes described in what follows:

MANAGERS

Users listed via the MANAGERS attribute are granted full control over all jobs submitted to or running within the specified class.

# allow john and steve to cancel and modify all jobs submitted to the class/queue special
CLASSCFG[special] MANAGERS=john,steve

In particular, a class manager can perform the following actions on jobs within a class/queue:

• view/diagnose job (checkjob)
• cancel, requeue, suspend, resume, and checkpoint job (mjobctl)
• modify job (mjobctl)

JOBPROLOG

The JOBPROLOG class performs a function similar to the resource manager level job prolog feature; however, there are some key differences:

• Moab prologs execute on the head node; resource manager prologs execute on the nodes allocated to the job.
• Moab prologs execute as the primary Moab administrator, resource manager prologs execute as root.
• Moab prologs can incorporate cluster environment information into their decisions and actions. (See Valid Variables.)
• Unique Moab prologs can be specified on a per class basis.
• Job start requests are not sent to the resource manager until the Moab job prolog is successfully completed.
• Error messages generated by a Moab prolog are attached to jobs and associated objects; stderr from prolog script is attached to job.
• Moab prologs have access to Moab internal and peer services.

Valid epilog and prolog variables are:

The JOBPROLOG class attribute allows a site to specify a unique per-class action to take before a job is allowed to start. This can be used for environmental provisioning, pre-execution resource checking, security management, and other functions. Sample uses may include enabling a VLAN, mounting a global file system, installing a new application or virtual node image, creating dynamic storage partitions, or activating job specific software services.

A prolog is considered to have failed if it returns a negative number. If a prolog fails, the associated job will not start.

If a prolog executes successfully, the associated epilog is guaranteed to start, even if the job fails for any reason. This allows the epilog to undo any changes made to the system by the prolog.

Job Prolog Examples

# explicitly specify prolog arguments for special epilog
CLASSCFG[special] JOBPROLOG='$TOOLSDIR/specialprolog.pl $JOBID $HOSTLIST'
# use default prolog arguments for batch prolog
CLASSCFG[batch]   JOBPROLOG=$TOOLSDIR/batchprolog.pl

JOBEPILOG

The Moab epilog is nearly identical to the prolog in functionality except that it runs after the job completes within the resource manager but before the scheduler releases the allocated resources for use by subsequent jobs. It is commonly used for job clean-up, file transfers, signaling peer services, and undoing other forms of resource customization.

An epilog is considered to have failed if it returns a negative number. If an epilog fails, the associated job will be annotated and a message will be sent to administrators.

RESFAILPOLICY

This policy allows specification of the action to take on a per-class basis when a failure occurs on a node allocated to an actively running job. See the Node Availability Overview for more information.

DISABLEAM

You can disable allocation management for jobs in specific classes by setting the DISABLEAM class attribute to TRUE. For all jobs outside of the specified classes, allocation enforcement will continue to be enforced.

# do not enforce allocations on low priority and debug jobs
CLASSCFG[lowprio]  DISABLEAM=TRUE
CLASSCFG[debug]    DISABLEAM=TRUE

Setting Default Classes

In many cases, end-users do not want to be concerned with specifying a job class/queue. This is often handled by defining a default class. Whenever a user does not explicitly submit a job to a particular class, a default class, if specified, is used. In resource managers such as TORQUE, this can be done at the resource manager level and its impact is transparent to the scheduler. The default class can also be enabled within the scheduler on a per resource manager or per user basis. To set a resource manager default class within Moab, use the DEFAULTCLASS attribute of the RMCFG parameter. For per user defaults, use the CDEF attribute of the USERCFG parameter.

Creating a Remap Class

If a single default class is not adequate, Moab provides more flexible options with the REMAPCLASS parameter. If this parameter is set and a job is submitted to the remap class, Moab attempts to determine the final class to which a job belongs based on the resources requested. If a remap class is specified, Moab compares the job's requested nodes, processors, memory, and node features with the class's corresponding minimum and maximum resource limits. Classes are searched in the order in which they are defined; when the first match is found, Moab assigns the job to that class.

Because Moab remaps at job submission, updates you make to job requirements after submission will not cause any class changes. Moab does not restart the process.

In order to use REMAPCLASS, you must specify a DEFAULTCLASS. For example:

RMCFG[internal] DEFAULTCLASS=batch

In the example that follows, a job requesting 4 processors and the node feature fast are assigned to the class quick.

# You must specify a default class in order to use remap classes
RMCFG[internal]   DEFAULTCLASS=batch

# Jobs submitted to 'batch' should be remapped
REMAPCLASS        batch

# stevens only queue
CLASSCFG[stevens] REQ.FEATURES=stevens REQUIREDUSERLIST=stevens,stevens2

# Special queue for I/O nodes
CLASSCFG[io]      MAX.PROC=8 REQ.FEATURES=io

# General access queues
CLASSCFG[quick]   MIN.PROC=2 MAX.PROC=8 REQ.FEATURES=fast|short
CLASSCFG[medium]  MIN.PROC=2 MAX.PROC=8
CLASSCFG[DEFAULT] MAX.PROC=64
...

The following attributes can be used to remap jobs to different classes:

• MIN.PROC
• MAX.PROC
• MIN.WCLIMIT
• MAX.WCLIMIT
• REQ.FEATURES
• REQ.FLAGS=INTERACTIVE
• REQUIREDUSERLIST

If the parameter REMAPCLASSLIST is set, then only the listed classes are searched and they are searched in the order specified by this parameter. If none of the listed classes are valid for a particular job, that job retains its original class.

The remap class only works with resource managers that allow dynamic modification of a job's assigned class/queue.

If default credentials are specified on a remap class, a job submitted to that class will inherit those credentials. If the destination class has different defaults credentials, the new defaults override the original settings. If the destination class does not have default credentials, the job maintains the defaults inherited from the remap class.

Class Attribute Overview

The following table enumerates the different parameters for CLASSCFG.

Setting DEFAULT.* on a class does not assign resources or features to that class. Rather, it specifies resources that jobs will inherit when they are submitted to the class without their own resource requests. To configure features, use NODECFG.

CLASSCFG[viz] DEFAULT.GRES=viz:2

CLASSCFG[viz] DEFAULT.NODE=5

CLASSCFG[amd] DEFAULT.NODESET=ONEOF:FEATURE:ATHLON,OPTERON

CLASSCFG[intel] EXCL.FEATURES=ATHLON,AMD

CLASSCFG[batch] EXCL.FLAGS=INTERACTIVE

CLASSCFG[batch] FORCENODEACCESSPOLICY=SINGLEJOB

CLASSCFG[batch] HOSTLIST=r:abs[45-113]

CLASSCFG[batch] JOBFLAGS=restartable

CLASSCFG[fast] MANAGERS=root,kerry,e43

CLASSCFG[batch] MAX.NODE=64

CLASSCFG[small] MAX.PROC[USER]=3,6

CLASSCFG[long] MAX.WCLIMIT=96:00:00

CLASSCFG[dev] MIN.NODE=16

CLASSCFG[dev] MIN.PROC=32

CLASSCFG[batch] NODEACCESSPOLICY=SINGLEJOB

CLASSCFG[batch] PARTITION=p12

CLASSCFG[batch] PRIORITY=1000

QDEF
Format	<QOSID>
Description	Default QoS for jobs submitted to this class. You may specify a maximum of four QDEF entries per credential. Any QoSes specified after the fourth will not be accepted. In addition to classes, you may also specify QDEF for accounts, groups, and users.
Example	CLASSCFG[batch] QDEF=base Jobs submitted to class batch that do not explicitly request a QoS will have the QoS base assigned.

CLASSCFG[batch] QDEF=base QLIST=base,fast,special,bigio

CLASSCFG[amd] REQ.FEATURES=ATHLON,AMD

CLASSCFG[orion] REQ.FLAGS=INTERACTIVE

CLASSCFG[jasper] REQUIREDACCOUNTLIST=testers,development

CLASSCFG[jasper] REQUIREDUSERLIST=john,u13,steve,guest

REQUIREDQOSLIST
Format	Comma-delimited list of QoSes
Description	List of QoSes allowed to access and use a class (analogous to *LIST for other credentials). The number of unique QoSes is limited by the Moab Maximum ACL limit, which defaults to 32.
Example	CLASSCFG[jasper] REQUIREDQOSLIST=hi,lo

CLASSCFG[special] SYSPRIO=100

Enabling Queue Complex Functionality

Queue complexes allow an organization to build a hierarchy of queues and apply certain limits and rules to collections of these queues. Moab supports this functionality in two ways. The first way, queue mapping, is very simple but limited in functionality. The second method provides very rich functionality but requires more extensive configuration using the Moab hierarchical fairshare facility.

Queue Mapping

Queue mapping allows collections of queues to be mapped to a parent credential object against which various limits and policies can be applied, as in the following example.

QOSCFG[general]   MAXIJOB[USER]=14  PRIORITY=20
QOSCFG[prio]      MAXIJOB[USER]=8   PRIORITY=2000
# group short, med, and long jobs into 'general' QoS
CLASSCFG[short]   QDEF=general FSTARGET=30
CLASSCFG[med]     QDEF=general FSTARGET=40
CLASSCFG[long]    QDEF=general FSTARGET=30 MAXPROC=200
# group interactive and debug jobs into 'prio' QoS
CLASSCFG[inter]   QDEF=prio  
CLASSCFG[debug]   QDEF=prio
CLASSCFG[premier] PRIORITY=10000

3.5-F QoS Credential

The concept of a quality of service (QoS) credential is unique to Moab and is not derived from any underlying concept or peer service. In most cases, the QoS credential is used to allow a site to set up a selection of service levels for end-users to choose from on a long-term or job-by-job basis. QoSes differ from other credentials in that they are centered around special access where this access may allow use of additional services, additional resources, or improved responsiveness. Unique to this credential, organizations may also choose to apply different charge rates to the varying levels of service available within each QoS. As QoS is an internal credential, all QoS configuration occurs within Moab.

QoS access and QoS defaults can be mapped to users, groups, accounts, and classes, allowing limited service offering for key users. As mentioned, these services focus around increasing access to special scheduling capabilities & additional resources and improving job responsiveness. At a high level, unique QoS attributes can be broken down into the following:

• Usage Limit Overrides
• Service Targets
• Privilege Flags
• Charge Rate
• Access Controls

QoS Usage Limit Overrides

All credentials allow specification of job limits. In such cases, jobs are constrained by the most limiting of all applicable policies. With QoS override limits, however, jobs are limited by the override, regardless of other limits specified.

QoS Service Targets

Service targets cause the scheduler to take certain job-related actions as various responsiveness targets are met. Targets can be set for either job queue time or job expansion factor and cause priority adjustments, reservation enforcement, or preemption activation. In strict service centric organizations, Moab can be configured to trigger various events and notifications in the case of failure by the cluster to meet responsiveness targets.

QoS Privilege Flags

QoSes can provide access to special capabilities. These capabilities include preemption, job deadline support, backfill, next to run priority, guaranteed resource reservation, resource provisioning, dedicated resource access, and many others. See the complete list in the QoS Facility Overview section.

QoS Charge Rate

Associated with the QoSes many privileges is the ability to assign end-users costs for the use of these services. This charging can be done on a per-QoS basis and may be specified for both dedicated and use-based resource consumption. The Per QoS Charging section covers more details on QoS level costing configuration while the Charging and Allocation Management section provides more details regarding general single cluster and multi-cluster charging capabilities.

QoS Access Controls

QoS access control can be enabled on a per QoS basis using the MEMBERULIST attribute or specified on a per-requestor basis using the QDEF and QLIST attributes of the USERCFG, GROUPCFG, ACCOUNTCFG, and CLASSCFG parameters. See Managing QoS Access for more detail.

Related topics 

• Identity Manager Interface
• Usage Limits