Migrate OpenAM to Apache Cassandra without Single Point of Failure

Initial Data Storage Scheme

Data Type	Storage Method	Fautl Tolerance Method	Disadvantages
OpenAM configuration	OpenDJ (localhost:1389)	Multi-master replication	Configuration update on a single node affects all nodes by replication.
CTS-Core Token Service (Session persistence)			Syncronisation payload processed on all nodes Read performance from single node restricted by single node performance. Replication failure could cause other nodes to read-only mode
Accounts repository (except AD)

Data Storage Scheme for the Number of Credentials >5 Million

Data Type	Storage Method	Fault Tolerance Method	Disadvantages
OpenAM configuration	OpenDJ (localhost:1389)	Local independent storage as a part of the distribution (war file)	Updating the configuration on one node does not affect other nodes (the nodes are completely independent)
CTS-Core Token Service (Session persistence)	Cassandra Cluster (tcp:9042)	Cluster without a single point of failure with geo-distribution and distribution by rack	Synchronization write payload is processed only on the nodes with the required replication level The reading load from one node is not limited to the performance of one node, but distributed according to the replication level. Node failure does cause replication stop according to the replication level
Accounts repository (except AD)

Migration Plan

1. Cluster hardware resources planning
2. Deploy the cluster according to the required level of fault tolerance
3. Provide network access OpenAM-> tcp:9042
4. Migration stages (can be done independently):
   1. Switch "CTS - Core Token Service (sessions)"
   2. Switch "Accounts repository (except AD)" with legacy data migration
   3. Switch "OpenAM configuration"

Fault Tolerance Level Planning

Datacenter

Defines geo-distributed storage fault tolerance.  

• Minimum number of data centers: 1
• The recommended number of data centers: 
  • at least two 
  • at least the same number of data centers used for application servers (OpenAM)
• Allowed data center fault tolerance mode:
  • Hot Spare: used for data processing for application servers (OpenAM)
  • Cold Spare: not used for data processing for application servers (OpenAM)

Rack

Minimum fault tolerance unit within a data center for data distribution within a data center, haves:

• Independent disk subsystem array
• Independent virtualization hypervisor (host system)

Amount calculation:

• Minimum quantity inside hot spare data center: 1, but not less than replication level inside the data center
• Minimum quantity inside cold spare datacenter: 1, but not less than replication level inside the datacenter

Node

Defines the unit of information storage and load inside the data center rack

An Example of a Recommended Minimum Configuration

Test

DataCenter	Type	Amount of Copies	Rack	% data	Node	% data
dc01	host	1	rack01	100%	dc01-rack01-node01	100%

Production

DataCenter	Type	Amount of Copies	Rack	data %	Node	data %
dc01	hot	1	rack01	100%	dc01-rack01-node01	50%
					dc01-rack01-node02	50%
		1	rack02	100%	dc01-rack02-node01	50%
					dc01-rack02-node02	50%
dc02	hot	1	rack01	100%	dc02-rack01-node01	50%
					dc02-rack01-node02	50%
		1	rack02	100%	dc02-rack02-node01	50%
					dc02-rack02-node02	50%

 

Allowed:

• Increase the data center amount without service interruption
• Increase the rack amount without service interruption
• Increase the node amount without service interruption
• Change the number of data copies inside the data center without service interruption

Hardware Requirements For a Single Node

Environment	CPU	RAM	Disk
Test	>=2	>=8	16G HDD
Production	>=8	>=32 ballon=off	64G SSD RAID