How about allowing multiple shadow databases?




17 years ago
6 years ago


(Reporter: philip, Assigned: justdave)





17 years ago
Take Mozilla, for example.  More than 50% of the time, my queries time out 
because the site is so popular, even though Mozilla has the shadow database 
feature enabled.

My suggestion is that Bugzilla allows the administrator to specify how many 
shadow databases to specify, and would then query the least-busy database.

I bet that Mozilla would rather use more hard drive space but make the database 
available to people 100% of the time.

Please consider this -- it will make the Bugzilla solution much more reliable 
and scalable.

The correct solution here is to use MySQL (or other DB) replication, rather than
attempt to reimplement it ourselves.

How would this speed anything up?  I can only imagine it slowing things down.

I don't see how there could be contention for the shadow database, the point is
you can have any number of readers at once.  I suppose if they were on different
hard drives it could possibly be better, but even that's dubious.
gerv: You've misunderstood this rfe. This isn't a request to create such dbs.
Its a request to, given a list of n databases which magically somehow exist,
rotate between them. This would require my replication patch which, among other
things, connects to another database for the shadow db, instead of just using
USE statements.

Comment 4

17 years ago
It's true that I don't know the true reason for Bugzilla's slowness on Mozilla 
project... is it because the database is busy responding to other requests and 
I am enqueued for a long time?  Or is it because the machine cannot handle it, 

If it's because the database is busy, I thought it'd be logical to duplicate 
the data among multiple databases and as Bradley said, rotate between them to 
alleviate load.

Maybe even (and this is not easy, of course, but would be excellent for some 
projects) allow the administrator to specify the IP/port of several databases, 
so that those databases could be on different physical machines.  Of course, 
this may be useless if the bottleneck lies in the hardware or network 
connection instead of the database.
We already duplicate the data because of lock contention, duplicating it again
wouldn't make sense to reduce lock contention because there isn't any contention
in the shadow database.  This would only provide benefit for when you can place
them across extra disk drives.

Comment 6

17 years ago
Resolving to INVALID now that shadow databases are depreciated and support for
them is slated to be removed in the next versions.
Last Resolved: 17 years ago
Resolution: --- → INVALID
There will still be a shadow database feature, its just that it will use a
better implementation.
QA Contact: matty_is_a_geek → default-qa
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