(architecture) threading, memcached ... etc

[Pho Tek]

Goal

For the purpose of this post, let's just say I'm trying to design a system that sends email.

Description

The client enters:

source email address

destination email address

However the system will only accept a request if there is no pending request with the same source email address. Basically it takes about 30 seconds and maybe longer to complete a request!

e.g.

Request #1 ( [e-mail] to [e-mail] ) is accepted and now pending.

If I submit a new request ( [e-mail] to [e-mail] ) before the first request completes, system will reject it.

Current thoughts

I can easily do a sychronization on the source email address like this:

synchronized( source.intern() )
{
   // submit request
}

However this will not work in a cluster of webservers. What are my alternatives ?

Regards,

Pho

[Nick Kelly]

Hi Pho,

I assume if you're using a cluster of web servers you will have some sort of database to store information in?

If so, you could have a database table to hold pending request details.

Each time you receive a request to send an email you would check if there is already a corresponding row in the pending request table.
If there is you reject it.
If not, you add a row for it and then send the email.

When the email is sent you delete the row from the pending request table.

Hope that helps!