Listing existing queues

Listing existing queues

[Iñaki Baz Castillo]

Hi, is there any way to list the existing posix message queues? I mean
without habing to mount the posix mq filesystem.
I've not found how to do it with the C API provide by posix mq.

Thanks.

-- 
Iñaki Baz Castillo
<ibc@aliax.net>

Re: Listing existing queues

[Eric Wong]

Iñaki Baz Castillo <ibc@aliax.net> wrote:
> Hi, is there any way to list the existing posix message queues? I mean
> without habing to mount the posix mq filesystem.
> I've not found how to do it with the C API provide by posix mq.

Nothing that I know of, I do prefer the filesystem approach of Linux as
opposed to having a specialized API, though.

-- 
Eric Wong

Re: Listing existing queues

[Iñaki Baz Castillo]

2011/3/2 Eric Wong <normalperson@yhbt.net>:
> Nothing that I know of, I do prefer the filesystem approach of Linux as
> opposed to having a specialized API, though.

The problem is that if you provide a software that others can download
and use in their computers, you can not rely on the existence of the
filesystem approach :(

-- 
Iñaki Baz Castillo
<ibc@aliax.net>

Re: Listing existing queues

[Eric Wong]

Iñaki Baz Castillo <ibc@aliax.net> wrote:
> 2011/3/2 Eric Wong <normalperson@yhbt.net>:
> > Nothing that I know of, I do prefer the filesystem approach of Linux as
> > opposed to having a specialized API, though.
> 
> The problem is that if you provide a software that others can download
> and use in their computers, you can not rely on the existence of the
> filesystem approach :(

Yes.  However given the small number of POSIX message queue users and
systems supporting it, I still see the feature as being in the early
adopter phase and still has room to standardize on using the filesystem
like Linux.

And being early adopters of POSIX message queues, we (Ruby POSIX_MQ
users/developers) have some ability to impact the standardizing of
listing queues via the filesystem :)

Another thing I really, really like is that mq descriptors are mapped to
file descriptors in FreeBSD and Linux, so hopefully other kernel
implementers follow their lead and make it easy to poll()/select() on.

-- 
Eric Wong

Re: Listing existing queues

[Iñaki Baz Castillo]

2011/3/3 Eric Wong <normalperson@yhbt.net>:
> Yes.  However given the small number of POSIX message queue users and
> systems supporting it, I still see the feature as being in the early
> adopter phase and still has room to standardize on using the filesystem
> like Linux.
>
> And being early adopters of POSIX message queues, we (Ruby POSIX_MQ
> users/developers) have some ability to impact the standardizing of
> listing queues via the filesystem :)

Not sure if I understand you. Do you mean that, hopefully in a future
all the Linux/BDS systems will mount posix mqueues in the filesystem?
Some Linux kernels come without support for posix mq (not compiled).
Anyhow, assuming posix mq was widely adopted and extended, how could
we be sure that all the systems would use the same mount point?

Maybe I miss something, but I still think that a simple API funcion
"mq_list" which returns an array of char* representing each existing
mqueue name would be easier.

Cheers.

-- 
Iñaki Baz Castillo
<ibc@aliax.net>

Re: Listing existing queues

[Eric Wong]

Iñaki Baz Castillo <ibc@aliax.net> wrote:
> 2011/3/3 Eric Wong <normalperson@yhbt.net>:
> > Yes.  However given the small number of POSIX message queue users and
> > systems supporting it, I still see the feature as being in the early
> > adopter phase and still has room to standardize on using the filesystem
> > like Linux.
> >
> > And being early adopters of POSIX message queues, we (Ruby POSIX_MQ
> > users/developers) have some ability to impact the standardizing of
> > listing queues via the filesystem :)
> 
> Not sure if I understand you. Do you mean that, hopefully in a future
> all the Linux/BDS systems will mount posix mqueues in the filesystem?
> Some Linux kernels come without support for posix mq (not compiled).
> Anyhow, assuming posix mq was widely adopted and extended, how could
> we be sure that all the systems would use the same mount point?

The standard would be a filesystem mount point.  Things like /tmp/ and
/home/ are already more/less standardized nowadays.

Linux (following Plan 9's (and Unix's) lead that "everything is a file")
is already moving more and more things into the filesystem or file-like
features (signalfd/timerfd/eventfd) and avoiding specialized APIs for
signals/timers/events.

> Maybe I miss something, but I still think that a simple API funcion
> "mq_list" which returns an array of char* representing each existing
> mqueue name would be easier.

My personal preference is smaller APIs and more reuse of existing ones
whenever possible.

-- 
Eric Wong

Re: Listing existing queues

[Iñaki Baz Castillo]

2011/3/3 Eric Wong <normalperson@yhbt.net>:
> And being early adopters of POSIX message queues, we (Ruby POSIX_MQ
> users/developers) have some ability to impact the standardizing of
> listing queues via the filesystem :)

Hi Eric, I continue with same problem (of course, since there is not
yet standarization for mounting Posix MQ's in a specific path).

So, what can we do in order to "impact" in the standarizing of Posix
MQ mount mount? :)

-- 
Iñaki Baz Castillo
<ibc@aliax.net>

Re: Listing existing queues

[Eric Wong]

Iñaki Baz Castillo <ibc@aliax.net> wrote:
> 2011/3/3 Eric Wong <normalperson@yhbt.net>:
> > And being early adopters of POSIX message queues, we (Ruby POSIX_MQ
> > users/developers) have some ability to impact the standardizing of
> > listing queues via the filesystem :)
> 
> Hi Eric, I continue with same problem (of course, since there is not
> yet standarization for mounting Posix MQ's in a specific path).
> 
> So, what can we do in order to "impact" in the standarizing of Posix
> MQ mount mount? :)

Start using MQ more and get more people to use software that uses it.

Also go to the Linux Standards Base and try to get it in the new
Filesystem Hierchy Standard (to be finalized/released soon).

Try to get it into POSIX.

Also start talking to major distro maintainers/vendors to move towards
this.

Standardization is hard, and takes many years :)

-- 
Eric Wong

Re: Listing existing queues

[Iñaki Baz Castillo]

2011/6/21 Eric Wong <normalperson@yhbt.net>:
> Start using MQ more and get more people to use software that uses it.

Sure :)


> Also go to the Linux Standards Base and try to get it in the new
> Filesystem Hierchy Standard (to be finalized/released soon).
>
> Try to get it into POSIX.
>
> Also start talking to major distro maintainers/vendors to move towards
> this.
>
> Standardization is hard, and takes many years :)

And sometimes never happens :)

Thanks a lot.

-- 
Iñaki Baz Castillo
<ibc@aliax.net>