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Fri Oct 27 02:28:11 2000 UTC (23 years, 8 months ago) by harris41
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howto's and descriptions of system services associated with LON-CAPA -Scott

    1: <HTML>
    2: <HEAD>
    3: <TITLE>LON-CAPA Network Processes Documentation</TITLE>
    4: </HEAD>
    5: <BODY>
    6: <H1>LON-CAPA Network Processes Documentation</H1>
    7: <P>
    8: Scott Harrison
    9: </P>
   10: <P>
   11: Last updated: 10/26/2000
   12: </P>
   13: <H3>Introduction</H3>
   14: <P>
   15: This file describes issues associated with the basic network
   16: layer of the LON-CAPA system.  When upgrading, installing, or reconfiguring a LON-CAPA system,
   17: it is often necessary to stop and start the network processes so that the code
   18: they are running with is up-to-date.
   19: </P>
   20: <P><I>
   21: There are also secondary network layers associated with the LON-CAPA system
   22: which are discussed elsewhere in the <A HREF="http://install.lon-capa.org/docs/index.html">
   23: documentation</A>.  These include NFS, Appleshare, and Samba (Windows Network Neighborhood).
   24: </I></P>
   25: <P>
   26: There are two basic levels of client-server processes associated with
   27: implementing the LON-CAPA network.
   28: <OL>
   29: <LI><B>Web level</B>: LON-CAPA users communicate with the system through their web browser
   30: <LI><B>Server-to-server level</B>: LON-CAPA machines communicate with other LON-CAPA machines
   31: </OL>
   32: </P>
   33: <H3>Description</H3>
   34: <P>
   35: The web level is implemented through a web server.  LON-CAPA uses the Apache web server.
   36: The apache web server forks off daemon children (<TT>httpd</TT>) which handle client requests
   37: (http requests from web browsers on the internet).  The more http requests, the more daemon children are
   38: made available.
   39: </P>
   40: <P>
   41: LON-CAPA functionality is enabled in the web level through the use of mod_perl.  mod_perl
   42: allows perl modules to be compiled once, and reside in memory in order to coordinate the
   43: interaction of http requests with services and resources provided by the LON-CAPA server machine.
   44: </P>
   45: <P>
   46: The server-to-server level is implemented through forked system processes which communicate with the
   47: TCP/IP protocol.  There are two types of children processes that LON-CAPA server machines maintain.
   48: <OL>
   49: <LI><TT>lonc</TT>- proxy server processes, these allow a LON-CAPA machine to act as a client toward another machine
   50: <LI><TT>lond</TT>- remote command interpreter, these respond to the proxy server processes to allow a LON-CAPA machine
   51: to act as a server toward another machine
   52: </OL>
   53: </P>
   54: <P>
   55: Of course, it becomes exciting when information passed through the web level requires the server to retrieve
   56: data through the server-to-server (TCP/IP) level.  This is handled by a perl module (loaded with mod_perl) that
   57: interfaces to <TT>lonc</TT>.  This perl module is <TT>lonnet.pm</TT>.
   58: </P>
   59: <H3>Managing Network Processes the Normal Way (/etc/rc.d/init.d)</H3>
   60: <P>
   61: <BR>Log in as <TT>root</TT>.  
   62: <BR>To stop the web level: <TT>/etc/rc.d/init.d/httpd stop</TT>
   63: <BR>To start the web level: <TT>/etc/rc.d/init.d/httpd start</TT>
   64: <BR>To restart the web level: <TT>/etc/rc.d/init.d/httpd restart</TT>
   65: <BR>To look at the status of the web level: <TT>/etc/rc.d/init.d/httpd status</TT>
   66: <BR>To stop the server-to-server and web level: <TT>/etc/rc.d/init.d/loncontrol stop</TT>
   67: <BR>To start the server-to-server and web level: <TT>/etc/rc.d/init.d/loncontrol start</TT>
   68: <BR>To restart the server-to-server and web level: <TT>/etc/rc.d/init.d/loncontrol restart</TT>
   69: <BR>To look at the status of the server-to-server and web level: <TT>/etc/rc.d/init.d/loncontrol status</TT>
   70: </P>
   71: <H3>Managing Network Processes the Dirty Way (killing pids directly)</H3>
   72: <P>
   73: <FONT SIZE=+3>Log in as <TT>www</TT></FONT>.  <B>Do not enter these commands as root</B>.
   74: <BR>To stop the server-to-server level: <TT>kill `cat /home/httpd/perl/logs/*.pid`</TT>
   75: <BR>To start the server-to-server level: <TT>/home/httpd/perl/loncron</TT>
   76: <BR>To restart the server-to-server level: <TT>kill `cat /home/httpd/perl/logs/*.pid`; /home/httpd/perl/loncron</TT>
   77: <BR>To look at the status of the server-to-server level: <TT>ps auxwww | grep lonc; ps auxwww | grep lond</TT>
   78: </P>
   79: </BODY>
   80: </HTML>
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