[news.software.b] Cnews locking -- stale ones

pete@fidata.fi (Petri Helenius) (04/19/91)

  Is it:
A) already implemented
B) planned to be implemented
  that C-news software be capable of removing stale locks on the fly? It
should check the existence of the lock owner process and the if it's not
existent, remove that lock and wait for 5 seconds and try to lock it again.
  This should be a feature #defineable to off, because people run news with
nfs-mounted servers and there this could cause a mass trashing.
  Our site is working well and this is not a problem for our machines but
our upstream site gets stale locks from time to time and this cuts our
newsfeed quite badly.
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henry@zoo.toronto.edu (Henry Spencer) (04/19/91)

In article <PETE.91Apr18203829@fidata.fi> pete@fidata.fi writes:
>  Is it:
>A) already implemented
>B) planned to be implemented
>  that C-news software be capable of removing stale locks on the fly?

Neither.  This is documented in doc/interface and notebook/bdiffs.  Failure
of a locking protocol indicates that something is badly wrong.  Blindly
removing the lock and charging onward can be a terrible mistake.  We prefer
to alert the administrator (via "newswatch") and let him sort it out.

A side issue here is that one reason for having a lock persist for a long
time is that the administrator is working on the news system.

>It should check the existence of the lock owner process...

There is no portable way to do this.  Especially in the presence of
network file systems.

>our upstream site gets stale locks from time to time and this cuts our
>newsfeed quite badly.

They need to investigate *why* they are getting stale locks.  C News does
not do that.  Something is wrong.
-- 
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  henry@zoo.toronto.edu  utzoo!henry

peter@taronga.hackercorp.com (Peter da Silva) (04/20/91)

henry@zoo.toronto.edu (Henry Spencer) writes:
> They need to investigate *why* they are getting stale locks.  C News does
> not do that.  Something is wrong.

We get stale locks when the network file system loses a connection to the
news host machine. I'm not sure what we can do about it other than have
a human to occasionally give an enema to the news system. Suggestions
would be appreciated.
-- 
               (peter@taronga.uucp.ferranti.com)
   `-_-'
    'U`

henry@zoo.toronto.edu (Henry Spencer) (04/21/91)

In article <Q7F3W5C@taronga.hackercorp.com> peter@taronga.hackercorp.com (Peter da Silva) writes:
>We get stale locks when the network file system loses a connection to the
>news host machine. I'm not sure what we can do about it other than have
>a human to occasionally give an enema to the news system...

Our recommendation these days is that news processing should run on the
machine which has the disks, unless you have a network file system that
provides correct Unix filesystem semantics.  In particular, doing the
processing over an NFS connection is just too trouble-prone, due to NFS's
propensity for random misbehavior and semantic botches.  Reading news
over NFS is no problem -- NFS works acceptably as a read-only medium --
but manipulating files over it is a mistake.
-- 
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  henry@zoo.toronto.edu  utzoo!henry

peter@taronga.hackercorp.com (Peter da Silva) (04/21/91)

urlichs@smurf.sub.org (Matthias Urlichs) writes:
> If that network file system connection isn't reliable enough, it seems that
> there's a danger of something breaking in a bad way

I'm aware of this. We only do batching remotely: we rexec (similar
to rsh) rnews for incoming batches. The reason for doing the batching
remotely is to minimise the loss if a network connection drops: the
worst that can happen is a duplicate batch and a batch lock hanging
around until someone notices. Doing it the other way (for example,
rexecing uux) leads to lost batches.
-- 
               (peter@taronga.hackercorp.com)
   `-_-'
    'U`

peter@taronga.hackercorp.com (Peter da Silva) (04/21/91)

henry@zoo.toronto.edu (Henry Spencer) writes:
> processing over an NFS connection is just too trouble-prone, due to NFS's
> propensity for random misbehavior and semantic botches.  Reading news
> over NFS is no problem -- NFS works acceptably as a read-only medium --
> but manipulating files over it is a mistake.

That's OK. I wouldn't touch NFS with a ten foot pole. I'm using Intel's OpenNET
NFA which handles everything, including locking, named pipes, everything except
shared memory. In this case we have modems on one machine and the News disks
on another, and it's better to have duplicates and occasional locks hanging
than losing batches.

"networked file systems" is not yet equivalent to "NFS". Thank the deity of your
choice for that.
-- 
               (peter@taronga.hackercorp.com)
   `-_-'
    'U`

news@ideal.id.dk (Nick Sandru (news adm)) (04/22/91)

peter@taronga.hackercorp.com (Peter da Silva) writes:

>We get stale locks when the network file system loses a connection to the
>news host machine. I'm not sure what we can do about it other than have
>a human to occasionally give an enema to the news system. Suggestions
>would be appreciated.
>-- 
>               (peter@taronga.uucp.ferranti.com)
>   `-_-'
>    'U`

I made a script which cleans locks older than a preset interval (12 - 24 hours)
and old articles which may have been left out by an aborted expire.
It worked fine during the last 5 - 6 months

Long Haired Nick


-- 
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