Zend Framework: Zend_Mail_Transport_Queue Component Proposal

Table of Contents

1. Overview

Zend_Mail_Transport_Queue is designed to manage the delivery of a large volume of mail. It provides a number of backends by which to store the mail and then allows deferred delivery from the storage container using concrete transport methods from a separate script.

2. References

• PEAR Mail_Queue

3. Component Requirements, Constraints, and Acceptance Criteria

• This component will provide an interface to allow the creation of multiple backends.
• This component will not send mail after a developer-specified amount of retries.
• This component will allow the developer to pass any valid transport component to re-send mail.
• This component will provide a means for passing log instances.

4. Dependencies on Other Framework Components

• Zend_Mail
• Zend_Mail_Transport_Abstract

5. Theory of Operation

This transport type replaces an existing SMTP or Sendmail transport instance. A concrete storage adapter is instantiated (e.g. Zend_Mail_Transport_Queue_Db or Zend_Mail_Transport_Queue_File) and then used as the transport to dispatch mail in the usual manner.

A secondary script (run as a cron job, scheduled task or as a trigger during another script's execution) will then access the transport's static process method. During this time mail is processed and directed to a specified transport (e.g. SMTP or Sendmail) and sent as normal. Processing will be limited to an amount configurable by the developer. If a mail instance cannot be sent (i.e. throws a Zend_Mail_Transport_Exception or Zend_Mail_Protocol_Exception exception) the mail will be requeued for a specified amount of retries (default is 10).

When mail is processed (success or failure) Zend_Mail_Transport_Queue will also log the attempt if a Zend_Log adapter is made available. The content and format of the log message is also developer-configurable.

6. Milestones / Tasks

• Milestone 1: design notes will be published here
• Milestone 2: Working prototype checked into the incubator supporting use cases #1, #2, ...
• Milestone 3: Working prototype checked into the incubator supporting use cases #3 and #4.
• Milestone 4: Unit tests exist, work, and are checked into SVN.
• Milestone 5: Initial documentation exists.

7. Class Index

• Zend_Mail_Transport_Queue_Interface
• Zend_Mail_Transport_Queue_Abstract
• Zend_Mail_Transport_Queue_Db
• Zend_Mail_Transport_Queue_File

8. Use Cases

9. Class Skeletons