Last activity: 18 Dec 2018 9:11 EST
Custom Passivation Mechanism VS Default Passivation Mechanism @ High Availability.
Could you please let us know how to decide upon the type (Custom vs Default) of Passivation Mechanism to be implemented wrt High Availability.
As far as i am concerned i want to go with custom passivation mechanism if i find that default features provided by Pega are not resilient enough in crash recovery / other fault tolerant use-cases . But Pega's OOTB default mechanism suffices for most of the use-cases
Pega's default passivation mechansim stores all the passivated data in database (until & unless there is single point of failure and no recovery of database - high availability might not have any impact ). With Custom mechanism one should rely on custom programming or available open source memory caching solutions which requires testing all the features in and out related to high-availability and passivation where as DEFAULT mechanism has already been tested by PEGA intensively .
Following links and documents might be helpful in understanding
Thank you for the information.
Could you please provide below mentioned details about the HA implementation.
1) Formula to calculate shared storage folder size.
Number of requestors * Clipboard size of each requestor * Number of Jvm's
Please correct if I miss anything.
2) Any hotfixes required to be installed for PEGA 718 @ HA implementation ?
Tata Consultancy Services Limited
High availability guide clearly states that OOTB supported shared storage mechanisms are not inherently fault tolerant.
PRPC supports shared storage using NFS or shared disk out of the box, but these solutions are not inherently fault tolerant
If there is a need for fault tolerant shared storage mechanism, does Pega recommend NOT to rely on OOTB mechanisms, but create a custom implementation using com.pega.pegarules.pub.session.CustomPassivationMechanism?
I'm trying to understand what is a fault tolerant shared storage mechanism being used in HA Pega implementations.
the link https://pdn.pega.com/creating-custom-passivation-method/creating-custom-passivation-method doesn't work anymore. I guess it's to the PDN article 66631 - "Creating a custom passivation method" which is missing. I can't find any article on custom passivation methods in the PDN. The sad part is, that the Pega High Availability Administratin Guides from Pega 7.1 to 7.3 still point to that missing article.
I've seen some references to an example for a custom passivation method from pega. It was backed by a memcached infrastructure. The implementation classname was com.pega.example.MemcachedPassivationMechanism. I can't find any links to that either. Is there some kind of reference implementation of the interface com.pega.pegarules.pub.session.CustomPassivationMechanism?
Maybe theres a way to leverage the PEGA-internal IMDG hazelcast or ignite to implement some kind of session replication across the pega cluster?
Any help would be appreciated.
Out of the box, Pega provides two passivation storage mechanisms: database and filesystem. When high availability is in effect (prconfig setting "session/ha/Enabled" is true), the default passivation storage is database; otherwise (as of 7.3.x) the default is filesystem. You can override the default storage mechanism by setting the prconfig setting "inititlization/persistrequestor/storage" to either "database", "filesystem", or "custom". Pega recommends that you use database passivation, which is most efficient and robust.
If you use custom storage, you must write a java class that implements com.pega.pegarules.pub.session.CustomPassivationMechanism. Internally in the Pega engine, this class is used as an input parameter when instanciating the out-of-the-box class CustomPassivationMechanismStorageAdapter. You must set the prconfig setting "initialization/persistrequestor/storage/custom/class" to the name of the class that you write.
The example that implements CustomPassivationMechanism is com.pega.example.MemcachedPassivationMechanism but it is only available in compiled form in a jar file.
I will work on correcting the invalid PDN/help links.
Any updates on the PDN links pointing to "Creating a Custom passivation method"
Hi Shiva, thanks for reminding me. Fixing the links fell through the cracks. I will update the help for the upcoming release to include the content I provided above, and to remove the comment about the link
could you share us some update about the link correction process? thanks.
The link to the updated 8.1 help is: https://community.pega.com/sites/default/files/help_v81/procomhelpmain.htm#engine/high-availability/quiesce/eng-high-availability-custom-passivation-mechanism-tsk.htm
Thanks for your quick reply.
i checked the help link.
so the article "Creating a custom passivation method" has been deleted from PDN. right?
the article still is recorded in Pega help version 73
Yes, we have been deleting obsolete articles from PDN. We do not retroactively update old help topics.