Re: [Erlyaws-list] Yapp - yaws applications updated to support ErlyWeb apps

[Mikael K. <mi...@cr...>]

Fri 09 Feb 2007 14:52 Roberto Saccon wrote:
> Mikael, I was thinking about giving yapp a try, but then I read your other,
> few days old mailpost titled "yapp isue",  where you say:
>
>  "Boring bug as it actually makes yapp unusable on R11B"
>
> - has this bug also been corrected in this patch ?
> (If not, it shouldn't it be mentioned in the doc that yapp does not work
> with R11B ?)

Sorry if I have confused you.
The bug was due to be fixed in R11B-3, but I was not able to verify this until 
a couple of days ago, after building the new erlang release. So the yapp 
handler (and hup on Yaws) will work for R11B-3, but not earlier revisions of 
Erlang/OTP R11B.

After verifying this I was able to add support for yapp "private" opaqes which 
makes it possible to make yapps out of ErlyWeb apps. (yesterday actually).
Note that it may take some time before the CVS commits shows up on 
the "anonymous" sourceforge.

> - Are URLs (of a yapped erlyweb application) without path (eg,:
> http://myserver.com/ ) possible ?

No, I just tested this, and it does not work for now, and
http://myserver.com// caused Yaws to go into spin, some more debugging
is needed here. But if you want to use no paths then using yaws.conf
might be your choice, since all accesses will be directed to the one and
same application. The point with yapps are that you can deploy several 
ones independently, but then you need the extra path to point out which
one to access. 

> And last question: in "yapp_intro.yaws" you say that yapp might in the
> future support clustered installations. Does that also include  porting the
> ets session table to a distributed mnesia table and replacing
> yaws_session_server.erl with a version for distributed mode ?

No, just how to be able to add/remove yapps on several distributed Yaws 
servers. 
The yapp handler uses mnesia today, and I was just thinking of using 
distributed mnesia and letting the yapp_server.erl subscribe on updates of 
the yapp registry in mnesia in order to capture updates from other nodes and 
not itself only. I guess starting doing this may raise other questions like 
the one you asked, but it may be good to separate concerns and leave sessions 
to Yaws. I have tried to make the yapp handler so independently as possible 
from Yaws (and ErlyWeb) so that it does not interfere with them but support 
them, and so it can be plugged in for those who likes it and also want to 
have more "Enterprise" support but also can live with the extra complexity 
that comes with mnesia and having to make real Erlang/OTP applications.

Actually I think the next step to go after (or before) adding distributed 
support would be to add some kind of release handling so that one also can do 
hot upgrade/downgrade/add/remove of yapps on running server(s). And also some 
kind of packaging support (like javas servlet.war files ... maybe). 

/Mikael