Bernese GPS Software Version 5.0 - Bernese GNSS Software

19. Bernese Processing Engine (BPE)
After the BPE server has been started, it performs the following tasks (see Figure 19.1):
(1) The BPE server reads its input options. The input options contain the name of the
Process Control File (PCF) and the CPU Control File. The first file defines the sequence
of tasks that will be executed and the second defines which hosts can be used.
These files are described in detail in Sections 19.4 and 19.5, respectively.
(2) According to the PCF and CPU file, the server starts the first client (it may happen
that several clients are started simultaneously). The CPU file defines how a client is
started. If the client is processed on a remote machine, the remote shell rsh or the
secure shell ssh command may be used.
(3) The first task of the newly started client is to open the TCP/IP connection to the
server. From the moment when the connection is accepted by the server, the client
is permanently connected until it terminates. Figure 19.2 displays the sequence of
communications between server and client.
(4) After successfully establishing the connection between server and client, the server
starts to send commands to the client and the client sends back its responses. The
first message from the server usually commands the client to run a specific user script
(see Section 19.6). The last response from the client informs the server about finishing
the user script. The last command from the server tells the client to disconnect and
terminate.
(5) In the way described above the BPE server keeps the information about all running
clients. After finishing one client the BPE server decides (according to the PCF)
whether new client(s) may be started. This means that steps (2) – (5) are repeated
until the entire BPE job finishes.
(6) Server and clients report the information about their execution into several output
files. See Section 19.10 for details.
19.3.2 BPE Client
The client of the BPE process is the single Perl module ${BPE}/RUNBPE.pm written in Perl
object-oriented style. As stated above the client is started by the BPE server. Figure 19.2
displays the sequence of communications between BPE server and BPE client. After being
started the client performs the following tasks:
(1) The client establishes the TCP/IP connection to the server. The needed information
(address and port number of the server) is received by the client as command
arguments when it is started.
(2) On server command the client prepares the environment and starts the user script
that resides in the directory ${U}/SCRIPT. The environment prepared by the client is
described in detail in Section 19.3.3.
(3) After the user script is finished (either successfully or with an error message), the
client reports back to the server.
(4) On server command the client closes the connection and exits.
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