20030604: LDM 6.0.12 not getting GEM data from dns2.cmc.ec.gc.ca.

Arthur and André,

> To: <address@hidden>
> From: "Arthur A. Person" <address@hidden>
> Subject: Problem with the data access via LDM ( Inidata) (fwd)
> Organization: UCAR/Unidata
> Keywords: 200306041302.h54D2PLd014788

The above message contained the following:

> We haven't been able to receive the GEM data from CMC since we upgraded to
> LDM 6.0.12.  You folks are apparently aware of this (as noted in my emails
> from CMC below) but I thought I would let you know we're having this
> trouble too.
> 
>                                 Art.
> 
> Arthur A. Person
> Research Assistant, System Administrator
> Penn State Department of Meteorology
> email:  address@hidden, phone:  814-863-1563

Thanks for letting us know.  In particular, thanks for including the
email from the CMC.

From our end, it appears that the operating system of the CMC host in
question has a bug that prevents a requesting LDM 6.0.12 from receiving
data. With an email address of a CMC contact, we can, hopefully, begin
to fix the problem.

In the meantime, you can fallback to using LDM 6.0.11 at the slight risk
of connecting to other, upstream LDM-s using the much less efficient
LDM-5 protocols.

Andre,

Bonjour!  Je suis aussi une Canadien -- but of the ex-patriot,
English-speaking variety. :-) I'm very glad to be sending you this email
(because I'm worried that my LDM 6.0.12 users are going to do something
nasty to me :-)

The problem seems to be with the RPC library used by the LDM on host
dns2.cmc.ec.gc.ca.  LDM 6.0.11 would sometimes connect to a restarted,
upstream LDM-6 using less efficient LDM-5 protocols due to a "window
of vulnerability" in the code and unlucky timing.  This window was
closed in version 6.0.12 by ensuring that LDM-5 protocols would only
be tried if the upstream RPC layer responded with the RPC error
RPC_PROGVERSMISMATCH.  I tested this change on almost all pairwise
combinations of the systems listed at

    
http://my.unidata.ucar.edu/content/software/ldm/ldm-6.0.12/install/supported-systems.html

In particular, it worked correctly for all downstream LDM-6's when
connecting to an upstream LDM-5 running on our IRIX 6.5.20m system.
For example, here's the log entry for a downstream LDM 6.0.12 connecting
to the upstream LDM-5 on our IRIX system:

    Jun 03 18:39:55 lenny.unidata.ucar.edu chevy[3571]: NOTICE: 
requester6.c:421; ldm_clnt.c:272: nullproc_6 failure to chevy.unidata.ucar.edu; 
ldm_clnt.c:141: RPC: Program/version mismatch; low version = 4, high version = 5
    Jun 03 18:39:55 lenny.unidata.ucar.edu chevy[3571]: Connected to upstream 
LDM-5
    Jun 03 18:39:55 lenny.unidata.ucar.edu chevy[3571]: 
FEEDME(chevy.unidata.ucar.edu): OK

When a downstream LDM-6.0.12 tries to connect to dns2.cmc.ec.gc.ca,
however, it receives an RPC_TIMEDOUT error rather than a
RPC_PROGVERSMISMATCH error.  This can be seen in the logfile of the
LDM 6.0.12:

    Jun 03 23:00:31 shemp.unidata.ucar.edu ftp[25926]: NOTICE: 
requester6.c:416; ldm_clnt.c:266: nullproc_6 failure to ftp.cmc.ec.gc.ca; 
ldm_clnt.c:140: RPC: Timed out

From Christian Pagé <address@hidden>, it appears that host 
dns2.cmc.ec.gc.ca is running a slightly older version of the IRIX 
operating sytem:

    The command uname -aR on dns2.cmc.ec.gc.ca gives the following:
    IRIX dns2 6.5 6.5.5f 07151439 IP22

I suspect that the RPC library of RIX 6.5 was upgraded or patched
between versions 6.5.5 and 6.5.20.  Our system administrator is going
to investigate this possibility around noon our time.  I'll keep you
apprised.

With regards,
Steve Emmerson
LDM Developer

>From address@hidden Wed Jun  4 10:27:14 2003
>To: "Dumas,Rejean [CMC]" <address@hidden>,
>   "Silva,Peter [CMC]" <address@hidden>
>Cc: address@hidden,
>  "Methot,Andre [CMC]" <address@hidden>,
>  "Arthur A. Person" <address@hidden>,
>  "'Steve Emmerson'" <address@hidden>


Rejean & Peter,

it appears that the operating system of the CMC host in
question has a bug that prevents a requesting LDM 6.0.12 from receiving
data.

Action is require at our end.

Thanks,
Andre Methot
Chief of Implementation & Operational Services

>From address@hidden Wed Jun  4 11:29:23 2003

Steve,

this file was passed on to the Data Acquisition & Distribution group.
Peter & Rejean, who receive copy of this note will be looking into this this
afternoon.

  The area I have control on, is the data production and GRIB encoding
(which works okay).

  However, you can keep me in the loop, as I'm concern about data services.

Regards,
Andre

-----Message d'origine-----
De : Steve Emmerson [mailto:address@hidden]
Envoye : 04 juin, 2003 12:26
A : Methot,Andre [CMC]
Cc : address@hidden
Objet : 20030604: LDM 6.0.12 not getting GEM data from
dns2.cmc.ec.gc.ca. 


Andre,

As a temporary workaround for our sites that upgraded to LDM 6.0.12
and also want the GEM data, could you add an ALLOW entry in your LDM-5
configuration file (ldmd.conf) for host atm.geo.nsf.gov (which is still
running version 6.0.10 of the LDM)?  We can then inform those sites to
switch their GEM request to host Atm.

Regards,
Steve Emmerson