Memcached为具有大量选择的小型数据库带来好处

Question

I am building a web app in php with mysql as database.

I am using memcached to store sessions and I am thinking if I should also store (in another memcached instance), database records.

The db is going to be pretty small and updated once in a while. There are going to be a lot of selects though, as we expect high traffic.

For a small database would I benefit if I store records in memcached or should I leave it to the mysql cache and tune the db for lots of connections (would appreciate some pointers for optimizing mysql)?

Thanks

Answer 1

Why dont you run some benchmarks and then spread that load !!

http://www.php.net/manual/en/intro.apc.php

Page generated in 0.003202 secs using 2 DB calls and 0 DBCache hits (users ttl=5 countries ttl=5 and both items have expired)

Page generated in 0.002728 secs using 1 DB calls and 1 DBCache hits (users ttl=5 countries ttl=immortal and users has expired)

Page generated in 0.000067 secs using 0 DB calls and 2 DBCache hits (users ttl=5 countries ttl=immortal and both are fetched from cache)

how fast - 0.000067 ouch !! 

Sample PHP Script using APC

<?php

require_once "CacheDB.php";

ob_start(); 

echo "<h3>APC info:</h3>";

print_r(apc_sma_info());

try{

    //I assume you've already have a db connection available for the cacheDB to use

    $db = @new mysqli("127.0.0.1","foo_dbo","pass","foo_db",3306);

    if ($db->connect_errno)
        throw new Exception("Could not connect: " . $db->connect_error);

    //start the demo...

    $startTime = microtime(true);

    $cacheDB = new CacheDB($db);

    $rows = $cacheDB->Query("call list_users()", CacheDB::TTL_5); //5 second Time To Live (TTL) (30 secs might be more realistic)
    if($rows){
        echo "<h3>Users:</h3><ul>";
        foreach($rows as $row) echo sprintf("<li>%s</li>", $row["username"]);
        echo "</ul>";
    }

    $rows = $cacheDB->Query("call list_countries()", CacheDB::TTL_IMMORTAL); //never expires

    if($rows){
        echo "<h3>Countries:</h3><ul>";
        foreach($rows as $row) echo sprintf("<li>%s</li>", $row["name"]);
        echo "</ul>";
    }

    echo sprintf("<p><b>Page generated in %s secs using %d DB calls and %d DBCache hits</b></p><p>Refresh me !!</p>",
            number_format(microtime(true) - $startTime, 6, ".", ""), 
            $cacheDB->GetDBHits(), $cacheDB->GetCacheHits());

    $db->close();
}
catch(Exception $ex)
{ 
    ob_clean(); 
    echo sprintf("zomg borked - %s", $ex->getMessage());
}

//finally

ob_end_flush();

?>