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  1. PO
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    <p>As maintainer of a fairly large C application that makes MySQL calls from multiple threads, I can say I've had no problems with simply making a new connection in each thread. Some caveats that I've come across:</p> <ul> <li><strong>Edit: it seems this bullet only applies to versions &lt; 5.5; see <a href="http://dev.mysql.com/doc/refman/5.7/en/c-api-threaded-clients.html" rel="noreferrer">this page for your appropriate version</a>:</strong> Like you say you're already doing, link against <code>libmysqlclient_r</code>.</li> <li>Call <a href="http://dev.mysql.com/doc/refman/5.0/en/mysql-library-init.html" rel="noreferrer"><code>mysql_library_init()</code></a> (once, from <code>main()</code>). Read the docs about use in multithreaded environments to see why it's necessary.</li> <li>Make a new <code>MYSQL</code> structure using <a href="http://dev.mysql.com/doc/refman/5.0/en/mysql-init.html" rel="noreferrer"><code>mysql_init()</code></a> in each thread. This has the side effect of calling <a href="http://dev.mysql.com/doc/refman/5.0/en/mysql-thread-init.html" rel="noreferrer"><code>mysql_thread_init()</code></a> for you. <code>mysql_real_connect()</code> as usual inside each thread, with its thread-specific MYSQL struct.</li> <li>If you're creating/destroying lots of threads, you'll want to use <a href="http://dev.mysql.com/doc/refman/5.0/en/mysql-thread-end.html" rel="noreferrer"><code>mysql_thread_end()</code></a> at the end of each thread (and <a href="http://dev.mysql.com/doc/refman/5.0/en/mysql-library-end.html" rel="noreferrer"><code>mysql_library_end()</code></a> at the end of <code>main()</code>). It's good practice anyway.</li> </ul> <p>Basically, don't share <code>MYSQL</code> structs or anything created specific to that struct (i.e. <code>MYSQL_STMT</code>s) and it'll work as you expect.</p> <p>This seems like less work than making a connection pool to me.</p>
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    1. POHow to access MySQL from multiple threads concurrently
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    1. USchazomaticus
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    1. POHow to access MySQL from multiple threads concurrently
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    1. COThis was just the kind of answer I needed. I didn't realize I'd have to call mysql_init in each thread -- I just did it once in main(). Thanks
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      1. USIsak Savo
    2. CO@chazomaticus, how many threads would you typically use and how many connections would you have open? Does this scale to large numbers of threads/connections? A connection pool is really useful if you have lots of threads (100's - 1000's) but don't want the overhead of opening 1000 connections (which you may not have permission to anyway as the default for max_connections is usually set at 100). If you have low numbers of threads then your approach would work. +1 from me for showing code examples.
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    3. COSince Isak is trying to stress the DB, as many threads as possible. I've run ~1000 without issue (if all the threads do is issue queries, most of their time is spent idle in `poll()`, so it's not as CPU-intensive as you might think, though it can eat a chunk of memory). You're right about max_connections capping you out at 100 by default, so for maximum stress, up that as desired.
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