perfSONAR User Q&A and Other Discussion

[Maciej Glowiak <>]

Hi Vedrin,

Sorry for such a long time without answer, but I've just finished my 
holidays.

Vedrin Jeliazkov napisał(a):
> Hi All,
>
> After having played with the recent versions of LS, I started to wonder if the
> concept of time-to-live (TTL) is implemented in the LS. I mean - what should
> happen if a given service registers with LS and unexpectedly fails later on.
> Should the LS remove the respective entry from its database after some TTL has
> elapsed after the last successful service registration? I expected to see such
> behaviour, but this doesn't happen in ISTF's LS (the record stays forever,
> unless an explicit de-register request is sent). We're running the latest
> snapshot (perfSONAR-LS-src-snapshot-20060720.tar.gz). I'm not sure if it is
> supposed to be that way or we have some problem with our specific LS
> installation/configuration.

Yes, a kind of TTL is supported. It's called LS Cleanup (in early 
deliverables it might have been called LS Sweeper).

> Another related question is - what's the purpose of the
> "component.ls_cleanup_loader.interval" - initially I presumed that this is in
> fact the above mentioned TTL, but I'm not so sure anymore...

Yes. The interval is defined as a time when Lookup Information is valid.

So, if a service is being registered, the current timestamp is stored as 
a parameter.
Scheduler which runs every N seconds checks all timestamps and if any of 
them is exceeded, the Lookup Information is removed.

So, if you set interval to 5 minutes, all not-updated-since-5-minutes 
services will be removed while running LS Cleanup scheduler action.

Each service activity (register, update, keepalive) will change the 
timestamp.

> The answers to the above questions are important for the development of
> perfsonarUI's interactions with LS. We have to know if the client could rely
> on the "freshness" of the records in LS or should check the registration
> timestamps and apply a TTL mechanism itself.

Of course it depends on the service configuration. It may be difficult 
for client if an administrator sets TTL for "one month".

Now the client has an access to control data, but it may be disabled in 
the future - personally I think the remote client shouldn't have rights 
for browsing control data directly. So maybe the "control" interface for 
the lookup service will be required in the future, something like: "Hey, 
LS, tell me what is your Lookup Information TTL?"

> Thanks for your comments and sorry for my laziness (I haven't thoroughly
> checked if this info is available in some document).

That's no problem.

Maciej

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| Maciej Glowiak        Network Research and Development            ||
| 

     Poznan Supercomputing and Networking Center ||
| (+48 61) 858 2024     http://monstera.man.poznan.pl/              ||
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