Olesen-FLEXlm-Integration

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Grid Engine 6 FlexLM License Integration (Olesen Method)

  • This document was last updated: ----fx Tue May 4 17:20:50 BST 2010
  • Computational chemistry software from Schrödinger was extensively used during the creation and testing of this document and the methods it describes. It is difficult to write about FLEXlm license integration without having licensed applications onhand to test with. The authors of this document would like to acknowledge and thank Schrödinger for their generous donation of software and licenses.

Background

Integrating license applications into Grid Engine systems is pretty easy if:

  • The application is unrestricted due to site-wide or enterprise licensing agreements
  • The application is node-locked to particular cluster nodes
  • The available license pool is larger than the number of job slots managed by Grid Engine
  • The license server and application is exclusive to the Grid Engine system (no external usage at all)


If you need to integrate a licensed application into a Grid Engine (aka N1GE) managed system, and any of the above conditions applies to your situation then consider yourself lucky as you will not need to use the methods described in this document. Node-locked applications can be handled via simple configuration of Grid Engine requestable resources and dedicated cluster license servers (where the cluster nodes are the only possible consumers of license tokens) can be easily handled via user requestable, consumable resources. Search the Grid Engine or N1GE documentation for the words highlighted in bold for specific implementation details.


This document is for people who need to handle multiple license servers scattered throughout an enterprise or instances where the Grid Engine cluster is not the sole consumer of license tokens. This document describes a new method of making the Grid Engine scheduler and resource allocation policy mechanisms aware of the ever changing license availibility data.


Readers are encouraged to follow and read the links located in the Primary References section. There is a significant amount of intro and background material contained in those links that is not duplicated here.

History

Mark Olesen, posting on the Grid Engine users list, made some very interesting comments about FlexLM license integration when Grid Engine load sensors are used for resource reporting. In particular, he proposed a method by which the entire load sensor process could be bypassed altogether in favor of methods that directly adjust the value of user requestable consumable resources within the Grid Engine complex.

Mark also mentioned that he was willing to share his code but that he did not have the time to handle user questions or any sort of support related duties. Chris Dagdigian volunteered to provide support via the http://gridengine.info site and the users@gridengine.sunsource.net mailing list.


Primary References

Additional Reference Material

The Proposed Methods

Problems With The Load Sensor Approach

An obvious problem with the load sensor approach is the delay associated with the load reports, as mentioned in the online documentation (see http://gridengine.sunsource.net/project/gridengine/howto/resource_management.html):

  Unfortunately, due to the loadsensor's delay, it can't be 100% excluded
  that batch jobs are dispatched and started although the license has been
  aquired by an interactive job.

The problem is actually much more serious than suggested by this warning! A race condition between a GridEngine job and an interactive job is less problematic than what actually occurs.

In the following examples, we'll examine how the licenses are managed with different approaches. For the sake of clarity, a new pseudo-variables internal_count and available have been introduced to reflect the current internal GridEngine state. The other variables - complex_values and load_values - are retrieved via qconf -se global.

The Pure Load Sensor Approach

Here the complex_values are left as NONE. The license availability is managed exclusively over the load sensor. This combination has the interesting side-effect that the internal bookkeeping is not used.

Consider the following:

Start:
    all licenses are available 

  load_values      license=4
  complex_values   NONE
  (internal_count) NONE
  (available)      license=4

Then:
   launch X jobs, each with -l license=4

Since all nodes provide resource license=4 and there is no internal bookkeeping to track the consumption of the resource, all jobs attempt to start at the same scheduling interval. Only one job wins the race and others fail with licensing problems.

A Combined Internal and Load Sensor Approach

Here the complex_values are set to the number of licenses available. The GridEngine decides on availability based on complex_values minus (internal_count) or the load_values. The lowest value dictates the availability, as mentioned in the online documentation (see http://gridengine.sunsource.net/project/gridengine/howto/loadsensor.html):

  The lesser of the Consumable Resources or the load sensor
  value will be used to prevent license oversubscription.

Consider the following:

Start:
    all licenses are available 

  load_values      license=4
  complex_values   license=4
  (internal_count) NONE
  (available)      license=4

Then:
   launch two jobs, each with -l license=4:
... \n

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