HP Integrity NonStop H-Series - Manual (Page 94)

There is a limit on the number of client connections a single instance of Post Master can handle.
As explained in JI, each connection results in a Pathsend dialog being established with the
serverclass. TS/MP limits the number of outstanding dialogs to 256 per requestor. In case of
NSASJ, the requestor process is the Post Master process. Hence, the number of client
connections that a Post Master can handle simultaneously is 256.
Number of CPUs
It is common to have at least one Post Master per CPU on all the CPUs selected for NSASJ
installation. This ensures that the requests routed to the NSASJ Server instances get properly
distributed across the link managers in the CPUs. Co-locating the Post Masters and the NSASJ
Servers can lead to reduced inter CPU messages leading to less load on the message system
interrupt processes.
System Load
In a heavily loaded system it might be desirable to have more than one Post Master per CPU.
A heavily loaded system is the one where there is lot of IPC messages flowing in the system.
This leads to high utilization (20-25% CPU-BUSY-TIME) of each of the message system interrupt
processes. When a Post Master is collocated in the IPU with the TSMSGIP processes, there
are chances that the Post Master does not get enough CPU bandwidth. Such a situation is
indicated by a near 100% utilization of the IPU. In such a situation having more than one Post
Master per CPU helps distribute the client connections across the instances.
Post Master and Measure Counters
Due to the nature of JI Pathsend BI-DIRECTIONAL channels that the Post Master is configured
to use, certain MEASURE entities and their counters provide useful information on the kind of
load the Post Master is handling. The subsequent topics tries to explain this:
PROCESS entity
The counters related to messaging indicate the activity between the Post Master and NSASJ
Server instances. To completely understand how these counters comprehend in NSASJ, it is
necessary to understand how JI BI-DIRECTIONAL channel works.
NOTE: To understand the discussion on counters related to messaging subsystem of the
PROCESS entity, it is necessary to completely understand how JI works. For more information,
see NonStop Server for Java Programmer’s Guide.
•
MSGS-SENT-QTIME: When this counter is viewed when the report rate is turned on
and the number indicates the average queue length. Now this counter indicates the
number of messages that are sent to the server process for which no response is obtained.
When related to JI BIDIRECTIONAL mode, this number provides a very close approximation
of the connections that are established for the instances in NSASJ-SERVER serverclass.
NOTE: Once a connection is successfully established with a server class instance, JI (in
BIDIRECTIONAL mode of operation) always keeps an open ended dummy message sent
to the server on its S2C channel. This dummy message is what adds to the
MSGS-SENT-QTIME counter. JI opens another channel called C2S channels. The messages
sent on this channel do not contribute to the MSGS-SENT-QTIME counter as the messages
are extremely short lived.
•
MESSAGES-SENT: This counter is the sum of messages sent over JI’s C2S and S2C channels.
The former uses Pathsend API and the later uses normal FS API. Normally, a single
invocation of an EJB results in two messages (one on each channel C2S and S2C) sent
to the NSASJ Server. See next immediate NOTE on the impact of send and receive buffer
sizes on the number of messages. Due to the nature of the JBoss Remoting (the library
used by JBoss Client and JBoss AS for remote invocations) a single EJB invocation can
result in more than two message exchanges too. Although, this counter cannot be used
to determine the actual number of business invocations in a particular time window, it
still provides a fair understanding of the activity in an NSASJ environment.
94 Internal description of NSASJ components