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   <h2>Session Three: lonsql (Gerd)</h2>  
   <p>This section describes issues associated with LON-CAPA and a SQL database.</p>  .Section2
   <p>The SQL database in LON-CAPA is used for catalog searches against resource  
     metadata only. The authoritative version of the resource metadata is Ð as   {page:Section2;}
     discussed Ð an XML-file on the normal file system (same file name as resource  
     plus Ò.metaÓ). The SQL-database is a cache of these files, and can be reconstructed  -->
     from the XML files at any time.</p>  
   <p>The current database is implemented assuming a non-adjustable architecture  </style>
     involving these data fields (specific to each version of a resource). </p>  
   <p> 1.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span>  </head>
     title </p>  
   <p> 2.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span>  <body bgcolor=#FFFFFF class="Normal" lang=EN-US>
     author </p>  
   <p> 3.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span>  <div class=Section1> 
     subject </p>  
   <p> 4.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span>    <h2>Session Three: lonsql (Gerd)</h2>
     notes </p>  
   <p> 5.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span>    <p>This section describes issues associated with LON-CAPA and a SQL database.</p>
     abstract </p>  
   <p> 6.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span>    <p>The SQL database in LON-CAPA is used for catalog searches against resource 
     mime </p>  
   <p> 7.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span>      metadata only. The authoritative version of the resource metadata is Ð as 
     language </p>  
   <p> 8.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span>      discussed Ð an XML-file on the normal file system (same file name as resource 
     creationdate </p>  
   <p> 9.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span>      plus Ò.metaÓ). The SQL-database is a cache of these files, and can be reconstructed 
     lastrevisiondate </p>  
   <p> 10.<span style='font:7.0pt "Times New Roman"'>&nbsp; </span> owner </p>      from the XML files at any time.</p>
   <p> 11.<span style='font:7.0pt "Times New Roman"'>&nbsp; </span> copyright </p>  
   <h3><a name="_Toc421867145">Purpose within LON-CAPA</a></h3>    <p>The current database is implemented assuming a non-adjustable architecture 
   <p>LON-CAPA is meant to distribute A LOT of educational content to A LOT of  
     people. It is ineffective to directly rely on contents within the ext2 filesystem      involving these data fields (specific to each version of a resource). </p>
     to be speedily scanned for on-the-fly searches of content descriptions. (Simply  
     put, it takes a cumbersome amount of time to open, read, analyze, and close    <p> 1.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     thousands of files.) </p>  
   <p>The solution is to hash-index various data fields that are descriptive of      title </p>
     the educational resources on a LON-CAPA server machine. Descriptive data fields  
     are referred to as &quot;metadata&quot;. The question then arises as to how    <p> 2.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     this metadata is handled in terms of the rest of the LON-CAPA network without  
     burdening client and daemon processes. I now answer this question in the format      author </p>
     of Problem and Solution below. </p>  
   <p><b>PROBLEM SITUATION:</b><span style='font-weight:normal'> If Server A wants    <p> 3.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     data from Server B, Server A uses a lonc process to send a database command  
     to a Server B lond process.</span></p>      subject </p>
   <p>&nbsp;&nbsp;&nbsp; lonc= loncapa client process&nbsp;&nbsp;&nbsp; A-lonc=  
     a lonc process on Server A</p>    <p> 4.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span> 
   <p>&nbsp;&nbsp;&nbsp; lond= loncapa daemon process</p>  
   <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;      notes </p>
     database command</span></p>  
   <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp; A-lonc&nbsp; --------TCP/IP----------------&gt;    <p> 5.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     B-lond</span></p>  
   <p>The problem emerges that A-lonc and B-lond are kept waiting for the MySQL      abstract </p>
     server to &quot;do its stuff&quot;, or in other words, perform the conceivably  
     sophisticated, data-intensive, time-sucking database transaction.&nbsp; By    <p> 6.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     tying up a lonc and lond process, this significantly cripples the capabilities  
     of LON-CAPA servers. </p>      mime </p>
   <p>While commercial databases have a variety of features that ATTEMPT to deal  
     with this, freeware databases are still experimenting and exploring with different    <p> 7.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     schemes with varying degrees of performance stability.</p>  
   <p><b>THE SOLUTION:</b><span style='font-weight:normal'> A separate daemon process      language </p>
     was created that B-lond works with to handle database requests.&nbsp; This  
     daemon process is called &quot;lonsql&quot;.</span></p>    <p> 8.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span> 
   <p>&nbsp; So,</p>  
   <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;      creationdate </p>
     database command</span></p>  
   <p><span style='font-family:"Courier New"'>&nbsp; A-lonc&nbsp; ---------TCP/IP-----------------&gt;    <p> 9.<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     B-lond =====&gt; B-lonsql</span></p>  
   <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;      lastrevisiondate </p>
     &lt;---------------------------------/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  
     |</span></p>    <p> 10.<span style='font:7.0pt "Times New Roman"'>&nbsp; </span> owner </p>
   <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  
     &quot;ok, I'll get back to you...&quot;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;    <p> 11.<span style='font:7.0pt "Times New Roman"'>&nbsp; </span> copyright </p>
     |</span></p>  
   <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;    <h3><a name="_Toc421867145">Purpose within LON-CAPA</a></h3>
     |</span></p>  
   <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;    <p>LON-CAPA is meant to distribute A LOT of educational content to A LOT of 
     &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/</span></p>  
   <p><span style='font-family:"Courier New"'>&nbsp; A-lond&nbsp; &lt;-------------------------------&nbsp;      people. It is ineffective to directly rely on contents within the ext2 filesystem 
     B-lonc&nbsp;&nbsp; &lt;======</span></p>  
   <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;      to be speedily scanned for on-the-fly searches of content descriptions. (Simply 
     &quot;Guess what? I have the result!&quot;</span></p>  
   <p>Of course, depending on success or failure, the messages may vary, but the      put, it takes a cumbersome amount of time to open, read, analyze, and close 
     principle remains the same where a separate pool of children processes (lonsql's)  
     handle the MySQL database manipulations.</p>      thousands of files.) </p>
 </div>  
 <br    <p>The solution is to hash-index various data fields that are descriptive of 
 clear=ALL style='page-break-before:always;'>  
 <div class=Section2> </div>      the educational resources on a LON-CAPA server machine. Descriptive data fields 
 </body>  
 </html>      are referred to as &quot;metadata&quot;. The question then arises as to how 
   
       this metadata is handled in terms of the rest of the LON-CAPA network without 
   
       burdening client and daemon processes. I now answer this question in the format 
   
       of Problem and Solution below. </p>
   
     <p><b>PROBLEM SITUATION:</b><span style='font-weight:normal'> If Server A wants 
   
       data from Server B, Server A uses a lonc process to send a database command 
   
       to a Server B lond process.</span></p>
   
     <p>&nbsp;&nbsp;&nbsp; lonc= loncapa client process&nbsp;&nbsp;&nbsp; A-lonc= 
   
       a lonc process on Server A</p>
   
     <p>&nbsp;&nbsp;&nbsp; lond= loncapa daemon process</p>
   
     <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   
       database command</span></p>
   
     <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp; A-lonc&nbsp; --------TCP/IP----------------&gt; 
   
       B-lond</span></p>
   
     <p>The problem emerges that A-lonc and B-lond are kept waiting for the MySQL 
   
       server to &quot;do its stuff&quot;, or in other words, perform the conceivably 
   
       sophisticated, data-intensive, time-sucking database transaction.&nbsp; By 
   
       tying up a lonc and lond process, this significantly cripples the capabilities 
   
       of LON-CAPA servers. </p>
   
     <p>While commercial databases have a variety of features that ATTEMPT to deal 
   
       with this, freeware databases are still experimenting and exploring with different 
   
       schemes with varying degrees of performance stability.</p>
   
     <p><b>THE SOLUTION:</b><span style='font-weight:normal'> A separate daemon process 
   
       was created that B-lond works with to handle database requests.&nbsp; This 
   
       daemon process is called &quot;lonsql&quot;.</span></p>
   
     <p>&nbsp; So,</p>
   
     <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   
       database command</span></p>
   
     <p><span style='font-family:"Courier New"'>&nbsp; A-lonc&nbsp; ---------TCP/IP-----------------&gt; 
   
       B-lond =====&gt; B-lonsql</span></p>
   
     <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   
       &lt;---------------------------------/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   
       |</span></p>
   
     <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   
       &quot;ok, I'll get back to you...&quot;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   
       |</span></p>
   
     <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   
       |</span></p>
   
     <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   
       &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/</span></p>
   
     <p><span style='font-family:"Courier New"'>&nbsp; A-lond&nbsp; &lt;-------------------------------&nbsp; 
   
       B-lonc&nbsp;&nbsp; &lt;======</span></p>
   
     <p><span style='font-family:"Courier New"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   
       &quot;Guess what? I have the result!&quot;</span></p>
   
     <p>Of course, depending on success or failure, the messages may vary, but the 
   
       principle remains the same where a separate pool of children processes (lonsql's) 
   
       handle the MySQL database manipulations.</p>
   
   </div>
   
   <br
   
   clear=ALL style='page-break-before:always;'>
   
   <div class=Section2> </div>
   
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