VOExplorer List Directory

Motivation

Simply listing MySpace directory contents in VOExplorer takes longer than seems reasonable. The aim is to try to isolate the which component is responsible for this slowness. There are several components that are involved in

Methodology

Network traffic from the local host to the various servers was captured using an OS level packet sniffing tool (wireshark) whilst listing the contents of a directly

Results

So from the point where I press the login button (or at least the first traffic I see as a result of it) (time in seconds in first column)

There is a shocking finding from the above - it is sometimes taking the registry about 5 seconds to respond to a "lookup ivorn" query (which should be the simplest - i.e. do not depend on complex search) - in fact it seems that "every second query" takes a long time.... - however, the "fast response" is within 0.2 seconds - clearly if 10 seconds (the two slow registry queries in the above) were removed from the above sequence the time to first display of home myspace contents would be relatively snappy 1.5 seconds.

After seeing these result GaryGilchrist pointed out that galahad.star.le.ac.uk was acting as a proxy for the real registry implementation on rakaposhi.star.le.ac.uk, which has the dns alias of registry.astrogrid.org. The test was rerun with the VOExplorer set directly to point at registry.astrogrid.org and the 5second delays disappeared.

Conclusions

It seems that there was something wrong with the proxying that was occurring on galahad. It would be worth investigating this further to avoid making the same mistake in the future. The main recommendation is, however, to configure clients and services to point to the DNS alias registry.astrogrid.org, which can be adjusted to point directly to the operational registry. Using this alias is better than using a specific machine name, beacause that required a proxy to be installed on the original machine (galahad) when the registry was physically moved in order to avoid having to reconfigure all the services/clients to point to the new registry.

-- PaulHarrison - 11 Jan 2008