467037 - Auto-Sync improvement: new e-mail download policy change

Status: RESOLVED INVALID

(MailNews Core :: Backend, defect)

Description

[Emre Birol]

According to the current policy, if the serial model is selected, when new emails arrive during non-idle time, auto-sync immediately downloads first 60K (see kFirstGroupSizeLimit) worth of messages, if and only if there is no other pending* sibling** of the receiving folder in the priority queue.

Rational: Under the serial model, auto-sync limits itself to download one and only one folder of a particular imap account at any given time. Since
downloads of large messages can overflow to non-idle time, auto-sync makes a safe decision (and lazy one) by not starting a new download that might overlap with an on-going one, potentially.

Proposed improvement: Auto-Sync can make better decision by checking the status of pending siblings; If the status of the siblings are different than stDownloadInProgress then it can assume that it is safe to start a new download.  

Also, there is no guarantee that 

Since auto-sync doesn't have any control over on-going download operation, 

it assumes that if a sibling is in the priority queue, there

stops any on going download operation when system idle gives back the control to the user, there is no guarantee that  

The rational behind such limitation is since auto-sync 

*waiting its turn to get downloaded during the next system idle time
**sibling means another folder of the same imap account