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Include the EDP Technical Considerations page in the EDP page 

Change-Id: I28500da937082e63320387c5ad2ab6c275da18a7
Implements: blueprint docs-03
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Trevor McKay 2013-10-17 12:03:47 -04:00
parent 21b052581c
commit f687606f0c
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doc/source/userdoc/edp.rst
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@ -102,3 +102,40 @@ The general workflow for defining and executing a MapReduce job in Savanna is es
+-------------------------+-----------------------------------------+
The workflow is simpler when using existing objects. For example, to construct a new job which uses existing binaries and input data a user may only need to perform steps 3, 5, and 6 above. Of course, to repeat the same job multiple times a user would need only step 6.
EDP Technical Considerations
============================
There are a several things in EDP which require attention in order
to work properly. They are listed on this page.
Transient Clusters
------------------
EDP allows running jobs on transient clusters. That way the cluster is created
specifically for the job and is shut down automatically once the job is
finished.
Two config parameters control the behaviour of periodic clusters:
* periodic_enable - if set to 'False', Savanna will do nothing to a transient
cluster once the job it was created for is completed. If it is set to
'True', then the behaviour depends on the value of the next parameter.
* use_identity_api_v3 - set it to 'False' if your OpenStack installation
does not provide Keystone API v3. In that case Savanna will not terminate
unneeded clusters. Instead it will set their state to 'AwaitingTermination'
meaning that they could be manually deleted by a user. If the parameter is
set to 'True', Savanna will itself terminate the cluster. The limitation is
caused by lack of 'trusts' feature in Keystone API older than v3.
If both parameters are set to 'True', Savanna works with transient clusters in
the following manner:
1. When a user requests for a job to be executed on a transient cluster,
Savanna creates such a cluster.
2. Savanna drops the user's credentials once the cluster is created but
prior to that it creates a trust allowing it to operate with the
cluster instances in the future without user credentials.
3. Once a cluster is not needed, Savanna terminates its instances using the
stored trust. Savanna drops the trust after that.