HP Integrity NonStop J-Series - Manual (Page 328)

you need the same n number of threads to process the new incoming requests. Therefore, the
number of threads that must be configured is (n + n = 2n).
•
The maximum number of connector threads, maxThreads must be equal to the value of
TANDEM_RECEIVE_DEPTH
.
For example:
The parameters Maxlinks, TANDEM_RECEIVE_DEPTH, and the connector threads are closely
linked to each other. These parameters are explained using examples. The following examples
assume that the httpd processes are configured to serve 100 simultaneous HTTP requests, and
all 100 HTTP requests are serviced by the application deployed in NSJSP (that is, there is no static
content in the application). Also, the peak load that one single instance of NSJSP can handle is
25.
Because the SessionBasedLoadBalancing feature is turned OFF, all messages between HTTPD
and NSJSP flow through TS/MP. The number of simultaneous messages that can be delivered to
an instance of NSJSP is determined by the value of Maxlinks; set the value of Maxlinks to 25.
NSJSP can now read 25 messages from its $RECEIVE queue simultaneously. In an extreme case
where all the 25 messages time out, there must be enough space in the $RECEIVE queue to
accommodate 25 more messages. Therefore, $RECEIVE must be opened with a Receive Depth
(controlled by TANDEM_RECEIVE_DEPTH) of (25+25). Thus, you must set the value of
TANDEM_RECEIVE_DEPTH
to 50. The reason for setting TANDEM_RECEIVE_DEPTH to a value
of 50 can be explained as:
NSJSP Configured with SessionBasedLoadBalancing Turned ON
•
The value of Numstatic must be [(Peak Load)/(Max load one instance of NSJSP
can handle)]
.
•
The value of Maxservers must be [(Peak Load)/(Max load one instance of
NSJSP can handle)]
. This ensures that no dynamic process is created, so that the session
object is not lost when there are many File System calls.
•
The value of Maxlinks must be set to the peak load that one instance of NSJSP is expected
to handle.
•
Arriving at a definite value for TANDEM_RECEIVE_DEPTH is difficult when NSJSP is configured
with SessionBasedLoadBalancing turned ON. Deciding an optimum value for
TANDEM_RECEIVE_DEPTH
requires a good understanding of the application. The following
example provides an insight into making this decision.
•
The maximum number of connector threads, maxThreads must be equal to the value of
TANDEM_RECEIVE_DEPTH
.
For example:
In this example, it is evident how a single instance of NSJSP, although having Maxlinks set to
25, can serve all the 100 requests.
Because SessionBasedLoadBalancing is turned ON, all messages between HTTPD and
NSJSP
flow through TS/MP and file system calls. The number of simultaneous messages that can
be delivered to an instance of NSJSP is determined by the value of Maxlinks; set the value of
Maxlinks
to 25.
With Maxlinks set to 25, a single instance of NSJSP can handle 25 concurrent requests through
TS/MP, all being the first requests of web dialogs. The first call on a web dialog is always delivered
to NSJSP through TS/MP and there will not be any file system call. After the 25 requests are
serviced, subsequent requests on those 25 web dialogs are delivered to NSJSP through file system
I/O operations.
At this stage, all 25 links to the NSJSP instance are free to process more incoming requests delivered
through TS/MP. Therefore, the NSJSP instance should now be able to handle 25 more concurrent
requests all being the first requests of web dialogs. After these 25 requests are processed, the
subsequent requests on these new connections arrive at NSJSP through the file system I/O. At this
stage, NSJSP could be handling up to 50 concurrent requests and all these requests are being
328 NonStop Specific Configurations