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POHuge and long sql query delay the php session_start() until query ends
 

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  1. POHuge and long sql query delay the php session_start() until query ends
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    <p>I got a cron that calls a php file and launches a huge SQL update on the database.</p> <p>something like that :</p> <pre><code>UPDATE t1 SET t1.a = (SELECT sum() FROM .... ) </code></pre> <p>This query takes seconds to execute (maybe 20sec).</p> <p>While the query is running, all the others scripts (from http or from cli) are delayed. Actually these scripts hold on the session_start() function.</p> <p>When the sql query ends, the other script (which were waiting on session_start() ) can run again (if they didn't reach the timeout) . </p> <p>The session uses file system as save handler.</p> <p>EDIT :</p> <p>Better explained in main steps :</p> <p><strong>I got 2 files</strong> </p> <p>File 1 : cron.php : is launched by a cron </p> <ol> <li>sql connection</li> <li>huge sql queries</li> </ol> <p>cron.php :</p> <pre><code>&lt;?php mysql_connect('host', 'user', 'pass'); mysql_select_db('mydb'); mysql_query('UPDATE t1 SET t1.a=(SELECT SUM(t2.a) FROM t2 WHERE "some where clauses")'); mysql_query('UPDATE t1 SET t1.b=(SELECT SUM(t2.b) FROM t2 WHERE "some where clauses")'); mysql_query('UPDATE t3 SET t3.c=(SELECT SUM(t2.b) FROM t2 WHERE "some where clauses")'); </code></pre> <p>File 2 : index.php : http reachable</p> <ol> <li>session_start()</li> <li>some codes</li> </ol> <p>index.php:</p> <pre><code>&lt;?php // index.php echo "SESSION STARTING"; session_start(); echo "SESSION STARTED"; </code></pre> <p><strong>What happens :</strong></p> <ol> <li><p>a cron launches <code>php cron.php</code> </p></li> <li><p>someone browses the website he goes to index.php</p></li> <li><p>apache launches <code>index.php</code> </p></li> <li><p>index.php holds on <code>session_start()</code></p></li> <li><p>the cron job ends</p></li> <li><p><code>index.php</code> can run normally</p></li> </ol> <p>In alternative to the 6. if the script is too much long, then i can see the following lines in the logs :</p> <pre><code>Premature end of script headers mod_fcgid: read data timeout in 40 seconds </code></pre> <p>That means that the script spent 40 second trying to read the session file</p> <p>The question is what could be the link between mysql query and the session start and what could delay the session_start() ? </p> <p>The server runs on Debian 7.</p>
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    1. USSoufiane Ghzal
    1. USSoufiane Ghzal
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      1. POHuge and long sql query delay the php session_start() until query ends
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      1. VTUpMod
    2. VO
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      1. POHuge and long sql query delay the php session_start() until query ends
      1. USLeite
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    3. VO
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      1. VTUpMod
    1. COOK. But what is the question?
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      1. USjuergen d
    2. COUpdated : The question is what could be the link between mysql query and the session start and what could delay the session_start() ?
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      1. POHuge and long sql query delay the php session_start() until query ends
      1. USSoufiane Ghzal
    3. COTh delay is badly written code. Why are SQL queries running before things like session_start() are called.
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      1. USwebnoob
 

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