Pros and cons using IDLED?

[Ken Murchison]

Simon Matter wrote:
> 
> I have enabled compilation of idled in my newest RPM but am wondering
> whether that was a good idea. I have two questions:
> 
> 1) I was searching the archives and docs but still can't find a
> description of the advantages and drawbacks when using idled instead of
> poll. What are the drawback of possible problems I may face when using
> idled?

Being the guy that wrote idled, I guess I have to answer  ;)

The main advantage of idled versus polling is that you get event-driven
instant notification of message changes (new, delete, flag changes, etc)
in your client when IDLEing (light load on the server, because it only
checks the mailbox when told to).  With polling, you can can updates as
fast as 1 sec, but you can beat the crap out of the server if you have a
lot of users polling that much.

The downside of using idled is that it might not scale well.  I haven't
received any input from a large site using idled.

Keep in mind that idled (or polling) is only used when the client issues
the IDLE command.  The only mainstream client that I'm aware of that
uses IDLE is Outlook.


> 
> 2) I have read the man pages but still don't fully understand how things
> work.
> From the man page:
> =====
> imapidlepoll: 60
>   The  interval  (in  seconds) for polling the mailbox for changes while
> running the IDLE command.  This option is
>   used when idled can not be contacted or when polling is used
> exclusively.  The minimum value is 1.  A value of 0
>   will disable polling (and disable IDLE if polling is the only method
> available).
> =====
> 
> 60 is the default value for imapidlepoll. It means that unless specified
> otherwise, IDLE is always enabled, using polling or idled. Only setting
> it to 0 does in fact disable IDLE. The man pages also say that if idled
> can not be contacted, poll is used instead.
> My problem is now that I have compiled with idled but not enabled it in
> cyrus.conf. I then get following messages:
> /var/log/messages:Nov 22 22:26:56 xxl imapd[2594]: error sending to
> idled: 2
> Is this message only a warning message or does it mean I really have to
> start idled if it's compiled in?


If you compile with idled enabled, it expects it to be running.  IIRC,
it will try talking to idled a handful of times, and then give up (using
polling exclusively).

Ken
-- 
Kenneth Murchison     Oceana Matrix Ltd.
Software Engineer     21 Princeton Place
716-662-8973 x26      Orchard Park, NY 14127
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