Notes
In-class Notes
Lecture 11
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Databases
/var/spool/mail
- where email is stored
- one file per user
my mail inbox in /var/spool/mail/soma
Who accesses this file?
- mail client
- mail server
What happens if the mail server delivers mail while I'm going
through my email (deleting, filing)
- unless you lock it, you lose mail, mail client will overwrite
inbox and delete new messages
- solution: lock the inbox
create a soma.lock file
(inside it has the process ID of the accessing process)
This is a bad idea that does not scale
Instead, use a database
- concurrent access
- data persistence