MySQL to refresh memcached - php

Question

We have a web application running on LAMP stack, the application depends on various services. These services gets data from cache (memcached) which is being refreshed using cron (from MySQL). Cron processes are running every 5 mins.
In this approach we can not serve data which is updated recently as cache is getting refreshed every 5 mins.
Is there any mechanism exists which can trigger cache refresh as soon as data gets updated in MySQL?

Answer 1

I don't know if this is the best solution, but what you can do is create MySQL trigger which gets executed on insert/update/delete.
Inside that MySQL trigger execute a UDF. From that UDF you can execute any PHP script using sys_exec().
Read about Triggers
Read about UDF
Read about using sys_exec() and more

Answer 2

My solution for this problem was to have the MySQL query in a function with the memcached query, for example (in Python, because I don't know PHP, you can look at it an change it to PHP):
def insert(user,value):
#execute on memcached first
key="user:"+user
memcClient.set(key,value)
#then execute it on MySQL
cursor.execute("INSERT INTO tables VALUES (%s,%s)",(user,value))
db.commit()
And you will do the same for delete and update, sorry I couldn't do it in PHP, I'm just a teen coder, good luck.

Answer 3

What about identifying the mysql updation at php level only & refresh the memcache accordingly ?
<?php
if($update_db){ // if we need to update the db then update db & memcacache together !
// Code to Update the database ....
// Code to Reset the memcached keyvalue pair.
}
?>
In the approach suggested by Manu, we are using expensive db trigger which is actually not needed to achieve the cache update.