perfSONAR User Q&A and Other Discussion

[Brian Candler <>]

On 08/09/2015 19:26, Andrew Lake wrote:

Hi brian,

Looks like you figured out some of this on your own, but adding some more details inline. 

Thank you helping me get to grips with this!

The MeshConfig software generates grids as follows generally speaking:

- For a full mesh the top of a box is the results from the row -> column as reported by the row MA. The bottom is the results from row to column as reported by the column MA. Why it does this relates to your next question so I'll wait to answer it below.

- For a disjoint test the top is the result from row -> column as reported by the row MA and the bottom is  result from column -> row as reported by the column MA. The reverse direction is in the same box since by definition a the column host may not be in the row host list, so it's our one shot to capture the reverse result. 

Which MA is which gets even more confusing if you have hosts in your mesh with no_agent (meaning no MA). You can tell the MA being used by clicking on the "Statistics" vertical tab and reading the maURL variable. 

So in a disjoint group, where the "a" hosts are on the left (rows) and the "b" hosts are on the top (columns), is the force_bidirectional flag still honored? This would mean that:

- "a" schedules a->b and b->a tests, and stores them in its MA
- "b" schedules a->b and b->a tests, and stores them in its MA

However maddash only shows one test in each direction, as you explained. So does it show a->b tests from the "a" MA, and b->a tests from the "b" MA ??  This *appears* to be the case from what I've configured.

e.g. starting at
http://maddash-uon.kenet.or.ke/maddash-webui/index.cgi?grid=KENET%20Mesh%20Config%20-%20Core%20to%20Remote%20OWAMP%20Testing

the top and bottom half of the same box (the bottom-left one) took me to respectively

http://maddash-uon.kenet.or.ke/maddash-webui/details.cgi?uri=/maddash/grids/KENET+Mesh+Config+-+Core+to+Remote+OWAMP+Testing/pfsnr.moi-pop.e.kenet.or.ke/pfsnr.uon-pop.n.kenet.or.ke/Loss
http://maddash-uon.kenet.or.ke/maddash-webui/details.cgi?uri=/maddash/grids/KENET+Mesh+Config+-+Core+to+Remote+OWAMP+Testing/pfsnr.moi-pop.e.kenet.or.ke/pfsnr.uon-pop.n.kenet.or.ke/Loss+Reverse

The MA URLs displayed in those two pages (under the "Statistics" section) were
http://pfsnr.moi-pop.e.kenet.or.ke/esmond/perfsonar/archive
and
http://pfsnr.uon-pop.n.kenet.or.ke/esmond/perfsonar/archive
respectively, suggesting that each graph is taken from a different MA. But looking at the graphs, each one displays both forward and reverse.

Now I have tried setting force_bidirectional to 0. I wonder if it now configures a unidirectional test from a->b to be stored on a, and a unidirectional test from b->a to be stored on b ?  I'll find out in a few hours.

It does seem to me it would be more useful if it configured bi-directional tests on the b host only. Then the 'a' hosts could all be dumb beacons, without their own measurement archives, and not having to read the mesh config at all.

But it's still perfectly possible I have misunderstood all this :-)

Regards,

Brian.