HP Integrity NonStop H-Series - Manual (Page 93)

7 Internal description of NSASJ components
This chapter provides details about the various components of NSASJ through different questions
and answers. It also provides an insight into the internal working of NSASJ with various other
components outside NSASJ. In this edition, only Post Master and NSASJ Server internal details are
documented and the other components will get appended in subsequent versions of this manual.
Post Master internals
The following set of questions and answers helps in an in-depth understanding of the Post Master:
1. How does the Post Master internally work?
As already stated, the work of the Post Master is to act as a channel between the JEE client
(like EJB client) and NSASJ Server. It listens for new connections on server ports and with every
new connection it creates a new connection to the NSASJ server and exchanges data. The
Post Master is capable of handling large number of connections simultaneously. The
SocketChannels
that represent the connections are multiplexed by the Selector of the
java.nio package.
NOTE: The server port to bind and listen for new connections is represented by the
localPort attribute of the Proxy element in the configuration file.
While the Client to Post Master (C2P) channels are all TCP channels, the Post Master is
configured to create a Pathsend JI channel for all Post Master to Server (P2S) channels.
NOTE: The JI channels in Post Master are configured as BI-DIRECTIONAL PATHSEND JI
channels. The JI channels are no-waited in nature. For more information on JI, see NonStop
Server for Java 7.0 Programmer’s Reference manual.
A single instance of PostMaster can play the role of a proxy on multiple server ports. This
is represented by multiple proxy configuration elements. Internally, the PostMaster uses a
single Java thread per proxy and also uses a selector per proxy to multiplex the
SocketChannels
on that proxy. PostMaster internally uses ByteBuffers to transfer
data between the C2P and P2S channels. The ByteBuffers are allocated only once per
channel when the channel is created and reused.
2. How many Post Masters are needed?
A single instance of Post Master is capable of handling multiple connections simultaneously
and can drive the IPU to its peak utilization. One might want to start more than the default
number of Post Masters. There are a few factors that need to be considered to arrive at the
right number of Post Masters needed in an NSASJ installation.
NOTE: There is no rule or mathematical formula to determine the number of Post Masters.
The subsequent subsections try to explain factors to consider to arrive at an optimal number
of Post Masters for a particular NSASJ installation.
TCP/IP provider
The number of Post Masters that can be configured in an NSASJ installation depends on the
TCP/IP provider configured in the system.
If the provider is TCPIPv6, then there can be a maximum of one instance of the Post Master
per CPU. Any attempt of starting more than one instance in a CPU results in “Address already
in use”exception.
If the provider is IP-CIP, then there is no limit on the number of instances that can be started
per CPU. The only limit is system resources such as memory.
Number of concurrent client connections
Post Master internals 93