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version 1.9, 2000/01/16 06:39:39 version 1.10, 2000/01/17 01:24:27
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 % $OpenXM: OpenXM/doc/issac2000/session-management.tex,v 1.8 2000/01/16 03:15:49 noro Exp $  % $OpenXM: OpenXM/doc/issac2000/session-management.tex,v 1.9 2000/01/16 06:39:39 takayama Exp $
   
 \section{Session Management}  \section{Session Management}
 \label{secsession}  \label{secsession}
Line 11  OpenXM.  We assume that various clients and servers
Line 11  OpenXM.  We assume that various clients and servers
 establish connections dynamically and communicate to each  establish connections dynamically and communicate to each
 other. Therefore it is necessary to give a dynamical and unified  other. Therefore it is necessary to give a dynamical and unified
 method to start servers and to establish connections.  method to start servers and to establish connections.
 In addition to that, interruption of executions and debugging  In addition to that, interruption of executions and
 supports are necessary for interactive distributed computation.  debugging facilities
   are necessary for interactive distributed computation.
   
 %\subsection{Interface of servers}  %\subsection{Interface of servers}
 %  %
Line 42  When the launcher is invoked, the client 
Line 43  When the launcher is invoked, the client 
 informs the launcher of a port number for TCP/IP connection  informs the launcher of a port number for TCP/IP connection
 and the name of a server.  and the name of a server.
 \item The launcher and the client establish a connection with the  \item The launcher and the client establish a connection with the
 specified port number.  specified port number. One time password may be used to prevent
   launcher spoofing.
 \item The launcher creates a process and executes the server after  \item The launcher creates a process and executes the server after
 setting the data channel appropriately.  setting the data channel appropriately.
 \end{enumerate}  \end{enumerate}
   
 After finishing the above task as a launcher, the launcher process  After finishing the above task as a launcher, the launcher process
 acts as a control server and controls the server process created by  acts as a control server and controls the server process created by
 itself. As for a control server see Section \ref{control}.  itself. As to the control server see Section \ref{control}.
   
 As the data channel is used to exchange binary data,  As the data channel is used to exchange binary data,
 the byte order conversion is necessary when a  the byte order conversion is necessary when a
Line 85  to send signals to a server or to terminate a server.
Line 87  to send signals to a server or to terminate a server.
   
 A client can send a signal to an engine by using the control channel  A client can send a signal to an engine by using the control channel
 at any time. However, I/O operations are usually buffered,  at any time. However, I/O operations are usually buffered,
 which may cause troubles without care for remaining data in  which may cause troubles.
 the buffers.  To reset a server safely the following are required.  To reset a server safely the following are required.
   
 \begin{enumerate}  \begin{enumerate}
 \item A sending of an {\tt OX} message must be completed.  \item Any OX message must be a synchronized object in the sense of Java.
   
 As an {\tt OX} message is sent as a combination of several {\tt CMO}  As an {\tt OX} message is sent as a combination of several {\tt CMO}
 data, a global exit without sending all the data confuses the  data, a global exit without sending all may generate broken data.
 subsequent communication.  
   
 \item After restarting a server, a request from a client  \item After restarting a server, a request from a client
 must correctly corresponds to the response from the server.  must correctly corresponds to the response from the server.
Line 103  after restarting a server.
Line 104  after restarting a server.
 \end{enumerate}  \end{enumerate}
   
 {\tt SM\_control\_reset\_connection} is an {\tt SM} command to  {\tt SM\_control\_reset\_connection} is an {\tt SM} command to
 initiate a safe resetting of a server. We show the action of  initiate a safe resetting of a server.
 a server and a client from the initiation to the completion of  Under the OpenXM reset protocol a server and a client act as follows.
 a resetting.  
   
 \centerline{\fbox{client}}  \centerline{\fbox{client}}
   
Line 142  any special action to be executed by the server becaus
Line 142  any special action to be executed by the server becaus
 assured that the peer is in the resetting state when one has received  assured that the peer is in the resetting state when one has received
 {\tt OX\_SYNC\_BALL}.  {\tt OX\_SYNC\_BALL}.
   
 \subsection{Debugging supports}  \subsection{Debugging facilities}
 Debugging is not easy for distributed computations.  Debugging is not easy for distributed computations.
 If servers are executed on X window system, then the control server can  We provide two methods to help debugging.
 attach an {\tt xterm} to the standard outputs of the engine to display  If servers are executed on X window system,
 diagnostic messages from the engine.  the diagnostic messages from the engine are displayed in a {\tt xterm}
   window.
 Furthermore, if the engine provides an interface to input commands,  Furthermore, if the engine provides an interface to input commands,
 then debugging of user defined programs will be  then each engine can pop up a debug window.
 possible on the engine. For example {\tt ox\_asir}, which is  For example {\tt ox\_asir}, which is
 the OpenXM server of {\tt Risa/Asir}, can pop up a window to input  the OpenXM server of {\tt Risa/Asir}, can pop up a window to input
 debug commands and the debugging similar to that on usual terminals is possible.  debug commands and the debugging similar to that on usual terminals is possible.
 One can also send {\tt SIGINT} by using {\tt SM\_control\_to\_debug\_mode}  One can also send {\tt SIGINT} by using {\tt SM\_control\_to\_debug\_mode}
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