Tool to send email from a DB

Question

We are developing a webapp that needs to send out emails written in Java/Groovy. Currently, we are persisting each email to a database before we call the Java Mail APIs to send the mail to our SMTP server.

I want to send out email asynchronously. I want to persist the email and then have another process pick up the email and send it (and send it only once). Ideally, this process is running outside of my webapp.

Are there any tools that do that?

Update: This solution needs to prevent duplicate emails and it needs to handle spikes in email. I was hoping someone already wrote an offline email processor. (I'd rather not implement this myself.)

Answer 1

If you're using Linux/Unix you could create a cron job to run every few minutes which calls a program to grab the email from the database and send it out. You could also have a field in the database to indicate whether the message has been sent. The downside of this approach is that there may be a delay of a few minutes from when your webapp persists the email and when the cron job is run.

Answer 2

Setup a cron job and use scripts to query the db and send out emails via sendmail.

Answer 3

On the off chance it's an Oracle DB, you can use the UTL_MAIL package to write PL/SQL to send the mail through your SMTP server. Then create a scheduled job to execute on your desired schedule.

http://download.oracle.com/docs/cd/B19306_01/appdev.102/b14258/u_mail.htm

Answer 4

The suggestions to use a cron job to read the database are quite workable.

Another good approach here is to use a Java Message Service (JMS) message queue. These are persistent (backed up by a database) and reliable. You can have one or more producer programs enqueue messages with the relevant data in them, and then one or more consumers process the messages and dequeue them. All of this is set up for very high reliability, and you gain the flexibility of asynchronously decoupling the operations, which means during email spikes the message queue can grow larger until the consumers catch up with the spike. Another benefit is that the email goes out as soon as a consumer gets to it instead of on a timer. Plus, if you require high availability, you can have multiple consumers in case one goes down.

Check out Apache's ActiveMQ for a good open source implementation of JMS.

Answer 5

Since you are already using groovy, this might be an interesting tool to solve your problem

http://gaq.sourceforge.net/

Answer 6

You could use Quartz, a scheduling library (similar to cron), to schedule a recurring task that reads the DB and sends the emails. If you're using Grails, there's a Quartz plugin that makes working with Quartz a bit more Groovy.