Starting with ITRM Report
Center 3.6, a clustered middle tier is supported. Servers can be clustered
on the same physical machine or across multiple physical machines.
A clustered middle tier provides high availability, load balancing,
high performance, and scalability. For more information, see
SAS 9.4 Intelligence Platform: Middle-Tier Administration
GuideCustomers can cluster
either vertically or horizontally.
-
Vertical clustering provides cluster
nodes on the same machine. The SAS Deployment Wizard enables
you to specify the number of cluster nodes.
-
Horizontal clustering provides
a cluster node on multiple machine. You can deploy a middle-tier cluster
node at any time. (A middle-tier cluster node is an optional machine
that can be specified in your plan file.)
Separate logging facilities
for each application node are provided for both vertical and horizontal
clusters. The log file for each node is kept inside a separate folder
under configured log directory. The folder name is suffixed with number
of nodes available in cluster such as SASServer10_1, SASServer10_5,
or SASServer10_n.
SAS relies on session
affinity. Therefore, every request from a client is directed to the
same instance of application server that was used when the client
logged on. If this node goes down, then the session of the logged-in
user is replicated on other node that is available in the cluster.
This feature increases the high availability of the ITRM Report Center.
However, you might lose your work if your logged-in node goes down
in the following circumstances:
-
when you are in the process of
creating, viewing, editing, or deleting an object, such as a gallery,
a folder, or an album
-
when you are in the process of
opening an object, such as a gallery, a resource, or an album
-
when you are accessing a watch
list
In such cases, a message appears in the ITRM Report
Center application that advises you to redo the operation.
ITRM Report Center
maintains a cache of all report objects in the middle tier. This cache
is replicated across all nodes of the clustered middle tier. If your
login action connects to a node for which cache is being replicated,
the following message appears: The ITRM Report Center
cache build is in progress. Please log off and try again later. Contact
your ITRM Report Center Administrator for more information. When
the replication of the cache completes, you can connect to that node
again.
Note: If multiple requests are
being processed by a node and that node goes down, ITRM Report Center
might display more than one error message.