Re: [ovirt-devel] [Devel] [Engine-devel] vds_dynamic refactor

From: "Gilad Chaplik" <gchaplik(a)redhat.com&gt; To: "Yaniv Dary" <ydary(a)redhat.com&gt; Cc: "Liran Zelkha" <liran.zelkha(a)gmail.com&gt;, "Kobi Ianko" <kobi(a)redhat.com&gt;, devel(a)linode01.ovirt.org, "engine-devel" <engine-devel(a)ovirt.org&gt; Sent: Thursday, April 10, 2014 12:30:52 PM Subject: Re: [Devel] [Engine-devel] vds_dynamic refactor ----- Original Message ----- > From: "Yaniv Dary" <ydary(a)redhat.com&gt; > To: "Gilad Chaplik" <gchaplik(a)redhat.com&gt; > Cc: "Liran Zelkha" <liran.zelkha(a)gmail.com&gt;, "Kobi Ianko" > <kobi(a)redhat.com&gt;, devel(a)linode01.ovirt.org, "engine-devel" > <engine-devel(a)ovirt.org&gt; > Sent: Thursday, April 10, 2014 11:44:32 AM > Subject: Re: [Devel] [Engine-devel] vds_dynamic refactor > > > > ----- Original Message ----- > > From: "Gilad Chaplik" <gchaplik(a)redhat.com&gt; > > To: "Liran Zelkha" <liran.zelkha(a)gmail.com&gt; > > Cc: "Yaniv Dary" <ydary(a)redhat.com&gt;, "Kobi Ianko" <kobi(a)redhat.com&gt;, > > devel(a)linode01.ovirt.org, "engine-devel" > > <engine-devel(a)ovirt.org&gt; > > Sent: Thursday, April 10, 2014 11:07:12 AM > > Subject: Re: [Devel] [Engine-devel] vds_dynamic refactor > > > > ----- Original Message ----- > > > From: "Liran Zelkha" <liran.zelkha(a)gmail.com&gt; > > > To: "Yaniv Dary" <ydary(a)redhat.com&gt; > > > Cc: "Gilad Chaplik" <gchaplik(a)redhat.com&gt;, "Kobi Ianko" > > > <kobi(a)redhat.com&gt;, > > > devel(a)linode01.ovirt.org, "engine-devel" > > > <engine-devel(a)ovirt.org&gt; > > > Sent: Wednesday, April 9, 2014 4:22:39 PM > > > Subject: Re: [Devel] [Engine-devel] vds_dynamic refactor > > > > > > On Wed, Apr 9, 2014 at 3:34 PM, Yaniv Dary <ydary(a)redhat.com&gt; wrote: > > > > > > > > Why not move only status with changes a lot to statistics and leave > > > > everything as is? > > > > > > > > > > > Exactly. No need for a new table. Use the existing ones. > > > > Why should the dwh read entire dynamic record for each status > > change/available resources change? (for VMs as well). > > The DWH doesn't work like that. We create views over dynamic\statistics and > dynamic\static they go the the configuration and stats tables on the > history > db side. > From dynamic\statistics we collect every minute no matter what and from > dynamic\static we collect only when update_date changes in static. dynamic\statistics - dynamic\static to fully understand it, we have 2 triggers to collect from dynamic?

> We can not rely on the dynamic update_date since it changes so much, so > from > my point of view if we can cause minimal changes in dynamic and move status > to statistics it would the best thing. > What we have currently is a task that run once a hour and checks if any > change was made in the dynamic table (via very ugly joins and rejects) and > sync is there was any change. > It would even be better if you also move swap_size which doesn't change > much > to dynamic. > oh... I thought that we had a trigger to dynamic (if ^ is correct we have). +1 (out of 1) for you comment :-) and thanks Yaniv the elaborate explanation! > > > > > > > > > > > > > > > > > Yaniv > > > > > > > > ________________________________ > > > > > > > > From: "Liran Zelkha" <liran.zelkha(a)gmail.com&gt; > > > > To: "Gilad Chaplik" <gchaplik(a)redhat.com&gt; > > > > Cc: "Kobi Ianko" <kobi(a)redhat.com&gt;, devel(a)linode01.ovirt.org, > > > > "engine-devel" <engine-devel(a)ovirt.org&gt; > > > > Sent: Monday, April 7, 2014 8:51:00 AM > > > > > > > > Subject: Re: [Devel] [Engine-devel] vds_dynamic refactor > > > > > > > > > > > > > > > > > > > > On Sun, Apr 6, 2014 at 11:03 PM, Gilad Chaplik <gchaplik(a)redhat.com&gt; > > > > wrote: > > > >> > > > >> ----- Original Message ----- > > > >> > From: "Liran Zelkha" <liran.zelkha(a)gmail.com&gt; > > > >> > To: "Gilad Chaplik" <gchaplik(a)redhat.com&gt; > > > >> > Cc: "Kobi Ianko" <kobi(a)redhat.com&gt;, devel(a)linode01.ovirt.org, > > > >> > "engine-devel" <engine-devel(a)ovirt.org&gt; > > > >> > Sent: Sunday, April 6, 2014 8:51:02 PM > > > >> > Subject: Re: [Devel] [Engine-devel] vds_dynamic refactor > > > >> > > > > >> > On Sun, Apr 6, 2014 at 6:32 PM, Gilad Chaplik > > > >> > <gchaplik(a)redhat.com&gt; > > > >> > wrote: > > > >> > > > > >> > > ----- Original Message ----- > > > >> > > > From: "Liran Zelkha" <liran.zelkha(a)gmail.com&gt; > > > >> > > > To: "Kobi Ianko" <kobi(a)redhat.com&gt; > > > >> > > > Cc: "Gilad Chaplik" <gchaplik(a)redhat.com&gt;, > > > >> > > > devel(a)linode01.ovirt.org, > > > >> > > "engine-devel" <engine-devel(a)ovirt.org&gt; > > > >> > > > Sent: Sunday, April 6, 2014 3:40:13 PM > > > >> > > > Subject: Re: [Devel] [Engine-devel] vds_dynamic refactor > > > >> > > > > > > >> > > > On Sun, Apr 6, 2014 at 3:37 PM, Kobi Ianko <kobi(a)redhat.com&gt; > > > >> > > > wrote: > > > >> > > > > > > >> > > > > Joining in... > > > >> > > > > From my point of view, in real life a user should have that > > > >> > > > > many > > > >> > > > > VDSs > > > >> > > on > > > >> > > > > one Engine (from a DB point of view). > > > >> > > > > Modern DB system handles tables with millions of records and > > > >> > > > > many > > > >> > > > > relations, Do we really have a performance issue here? > > > >> > > > > We could prefer a more easy to maintain implantation in this > > > >> > > > > case > > > >> > > > > over > > > >> > > DB > > > >> > > > > performance > > > >> > > > > > > > >> > > > > Yes we do. We make many queries on the VDS view, which is a > > > >> > > > > VERY > > > >> > > complex > > > >> > > > view. > > > >> > > > > > > >> > > > > > >> > > Actually I quite agree with Kobi, what is the plan for VMs? why > > > >> > > do > > > >> > > we > > > >> > > start with VDS... > > > >> > > what is the biggest deploy do you know of? > > > >> > > > > > >> > We start with VDS because in an idle system, with 200 hosts and > > > >> > several > > > >> > thousands VMs, this is what you get as the top queries against the > > > >> > database. Look at how many times getvds is called. > > > >> > [image: Inline image 1] > > > >> > BTW - the second query is an example of abusing the dynamic query > > > >> > mechanism. The 4th query (an update command) is a set of useless > > > >> > update_vds_dynamic commands. > > > >> > > > > >> > For reference, the explain plan of get VDS is something like this: > > > >> > > > > >> > QUERY PLAN > > > >> > > > > >> > ----------------------------------------------------------------------------------------------------------------------------------------------------------- > > > >> > Nested Loop (cost=9.30..46.75 rows=6 width=9060) (actual > > > >> > time=0.063..0.068 rows=1 loops=1) > > > >> > Join Filter: (vds_static.vds_id = vds_statistics.vds_id) > > > >> > -> Seq Scan on vds_statistics (cost=0.00..1.01 rows=1 > > > >> > width=109) > > > >> > (actual time=0.008..0.008 rows=1 loops=1) > > > >> > -> Nested Loop (cost=9.30..45.64 rows=6 width=8983) (actual > > > >> > time=0.048..0.052 rows=1 loops=1) > > > >> > Join Filter: (vds_groups.vds_group_id = > > > >> > vds_static.vds_group_id) > > > >> > -> Nested Loop Left Join (cost=0.00..9.29 rows=1 > > > >> > width=1389) > > > >> > (actual time=0.013..0.013 rows=1 loops=1) > > > >> > -> Seq Scan on vds_groups (cost=0.00..1.01 rows=1 > > > >> > width=1271) (actual time=0.003..0.003 rows=1 loops=1) > > > >> > -> Index Scan using pk_storage_pool on > > > >> > storage_pool > > > >> > (cost=0.00..8.27 rows=1 width=134) (actual time=0.008..0.008 > > > >> > rows=1 > > > >> > loops=1) > > > >> > Index Cond: (vds_groups.storage_pool_id = id) > > > >> > -> Hash Right Join (cost=9.30..36.28 rows=6 width=7610) > > > >> > (actual > > > >> > time=0.033..0.037 rows=1 loops=1) > > > >> > Hash Cond: (vds_spm_id_map.vds_id = > > > >> > vds_static.vds_id) > > > >> > -> Seq Scan on vds_spm_id_map (cost=0.00..22.30 > > > >> > rows=1230 > > > >> > width=20) (actual time=0.003..0.003 rows=1 loops=1) > > > >> > -> Hash (cost=9.29..9.29 rows=1 width=7606) > > > >> > (actual > > > >> > time=0.019..0.019 rows=1 loops=1) > > > >> > Buckets: 1024 Batches: 1 Memory Usage: 2kB > > > >> > -> Nested Loop (cost=0.00..9.29 rows=1 > > > >> > width=7606) > > > >> > (actual time=0.012..0.013 rows=1 loops=1) > > > >> > -> Seq Scan on vds_dynamic > > > >> > (cost=0.00..1.01 > > > >> > rows=1 width=1895) (actual time=0.006..0.006 rows=1 loops=1) > > > >> > -> Index Scan using pk_vds_static on > > > >> > vds_static > > > >> > (cost=0.00..8.27 rows=1 width=5711) (actual time=0.005..0.006 > > > >> > rows=1 > > > >> > loops=1) > > > >> > Index Cond: (vds_id = > > > >> > vds_dynamic.vds_id) > > > >> > Total runtime: 0.299 ms > > > >> > (19 rows) > > > >> > > > > >> > It's terrible. Adding any additional join will make this worse. > > > >> > Please > > > >> > don't add any more tables... > > > >> > > > >> Thank you for the detailed explanation, my comments: > > > >> > > > >> * a very long time isn't an argument for not adding another table > > > >> (should > > > >> be neglectable); > > > >> currently we have an unrelated problem, we need to solve it. > > > > > > > > Of course it is. A very long time for a query that you execute many > > > > times > > > > is THE factor. Who said the join has no performance effect? Have you > > > > tested it? Under load? Under many writes/updates? > > > >> > > > >> > > > >> * > We start with VDS because in an idle system, with 200 hosts and > > > >> several > > > >> > thousands VMs, this is what you get as the top queries against the > > > >> > database. > > > >> > > > >> so, if fetching VMs takes 10 minutes? and its get called a single > > > >> time? > > > > > > > > Where do you see 10 minutes? If you are looking at the red bar it's > > > > the > > > > inherent time - total query time * number of queries. > > > >> > > > >> > > > >> * you didn't reply on my of my suggestion of constructing the VDS > > > >> records > > > >> in the DB without using joins. > > > > > > > > If you mean materialized views - we don't have it in Postgres just > > > > yet... > > > > And even if we do, since we do many updates to vds_statistics and > > > > vds_dynamic - I'm not sure it will have positive impact on our > > > > performance. If you mean joins in the database - everything that is > > > > based > > > > on VDS is done in the database. Part of the problem, since we can > > > > cache > > > > some information and only query the dynamic/statistics part of VDS, > > > > but > > > > that's another matter. > > > >> > > > >> > > > >> > > > >> > > > > >> > > > > > >> > > > > > > > >> > > > > ----- Original Message ----- > > > >> > > > > > From: "Gilad Chaplik" <gchaplik(a)redhat.com&gt; > > > >> > > > > > To: "Liran Zelkha" <liran.zelkha(a)gmail.com&gt; > > > >> > > > > > Cc: devel(a)linode01.ovirt.org, "engine-devel" > > > >> > > > > > <engine-devel(a)ovirt.org > > > >> > > > > > > >> > > > > > Sent: Sunday, April 6, 2014 3:32:26 PM > > > >> > > > > > Subject: Re: [Devel] [Engine-devel] vds_dynamic refactor > > > >> > > > > > > > > >> > > > > > ----- Original Message ----- > > > >> > > > > > > From: "Liran Zelkha" <liran.zelkha(a)gmail.com&gt; > > > >> > > > > > > To: "Gilad Chaplik" <gchaplik(a)redhat.com&gt; > > > >> > > > > > > Cc: "Itamar Heim" <iheim(a)redhat.com&gt;, > > > >> > > > > > > devel(a)linode01.ovirt.org, > > > >> > > > > > > "engine-devel" <engine-devel(a)ovirt.org&gt; > > > >> > > > > > > Sent: Sunday, April 6, 2014 3:26:24 PM > > > >> > > > > > > Subject: Re: [Engine-devel] vds_dynamic refactor > > > >> > > > > > > > > > >> > > > > > > On Sun, Apr 6, 2014 at 3:18 PM, Gilad Chaplik > > > >> > > > > > > <gchaplik(a)redhat.com > > > >> > > > > > > >> > > > > wrote: > > > >> > > > > > > > > > >> > > > > > > > ----- Original Message ----- > > > >> > > > > > > > > From: "Itamar Heim" <iheim(a)redhat.com&gt; > > > >> > > > > > > > > To: "Liran Zelkha" <liran.zelkha(a)gmail.com&gt; > > > >> > > > > > > > > Cc: "Gilad Chaplik" <gchaplik(a)redhat.com&gt;, > > > >> > > > > devel(a)linode01.ovirt.org, > > > >> > > > > > > > "engine-devel" <engine-devel(a)ovirt.org&gt; > > > >> > > > > > > > > Sent: Sunday, April 6, 2014 11:33:12 AM > > > >> > > > > > > > > Subject: Re: [Engine-devel] vds_dynamic refactor > > > >> > > > > > > > > > > > >> > > > > > > > > On 04/06/2014 11:32 AM, Liran Zelkha wrote: > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > On Sun, Apr 6, 2014 at 11:22 AM, Itamar Heim < > > > >> > > iheim(a)redhat.com > > > >> > > > > > > > > > <mailto:iheim@redhat.com>> wrote: > > > >> > > > > > > > > > > > > >> > > > > > > > > > On 04/03/2014 07:51 PM, Liran Zelkha wrote: > > > >> > > > > > > > > > > > > >> > > > > > > > > > The problem is with both updates and > > > >> > > > > > > > > > selects. > > > >> > > > > > > > > > For selects - to get all the information > > > >> > > > > > > > > > for > > > >> > > > > > > > > > the > > > >> > > > > > > > > > VDS > > > >> > > we > > > >> > > > > have > > > >> > > > > > > > > > multiple > > > >> > > > > > > > > > joins. Adding another one will hurt > > > >> > > > > > > > > > performance > > > >> > > > > > > > > > even > > > >> > > > > more. > > > >> > > > > > > > > > For updates - we have vds_static thats > > > >> > > > > > > > > > hardly > > > >> > > changed. > > > >> > > > > > > > > > vds_statistics > > > >> > > > > > > > > > that changes all the time. vds_dynamic is > > > >> > > > > > > > > > not > > > >> > > > > > > > > > changed > > > >> > > > > allot - > > > >> > > > > > > > but > > > >> > > > > > > > > > is > > > >> > > > > > > > > > updated all the time because of the > > > >> > > > > > > > > > status. > > > >> > > > > > > > > > I > > > >> > > > > > > > > > think > > > >> > > it's > > > >> > > > > best > > > >> > > > > > > > to > > > >> > > > > > > > > > split > > > >> > > > > > > > > > it to the two existing tables (BTW - > > > >> > > > > > > > > > relevant > > > >> > > > > > > > > > for VM > > > >> > > as > > > >> > > > > well) > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > but we don't update it unless the status has > > > >> > > > > > > > > > changed, > > > >> > > which > > > >> > > > > is a > > > >> > > > > > > > > > rare occurance? > > > >> > > > > > > > > > > > > >> > > > > > > > > > Actually - no. We can definitely see times we are > > > >> > > > > > > > > > updating > > > >> > > > > > > > > > vds_dynamic > > > >> > > > > > > > > > with no reason at all. I tried to create patches > > > >> > > > > > > > > > for > > > >> > > > > > > > > > that - > > > >> > > but > > > >> > > > > it > > > >> > > > > > > > > > happens from many different places in the code. > > > >> > > > > > > > > > > > >> > > > > > > > > what would be updated vds_dyanmic for status not > > > >> > > > > > > > > originating in > > > >> > > > > update > > > >> > > > > > > > > run time info? > > > >> > > > > > > > > > > >> > > > > > > > We have separate DB flows for that (updateStatus and > > > >> > > > > > > > updatePartialVdsDynamicCalc and more in > > > >> > > VdsDynamicDAODbFacadeImpl). > > > >> > > > > > > > A question: do you know if we update status in > > > >> > > > > > > > updateVdsDynamic? > > > >> > > :-) > > > >> > > > > not > > > >> > > > > > > > sure but I found a possible race for pending resources > > > >> > > > > > > > (cpu, > > > >> > > mem), > > > >> > > > > LOL > > > >> > > > > > > > :-) > > > >> > > > > > > > > > > >> > > > > > > > I think we do but not sure. Will check. > > > >> > > > > > > > > >> > > > > > Of course it is, that was a rhetorical question :-) (a lot > > > >> > > > > > of > > > >> > > emoticons > > > >> > > > > and > > > >> > > > > > LOLs ;-)) > > > >> > > > > > > > > >> > > > > > > > > > >> > > > > > > > > > >> > > > > > > > Still holds my original thought for having > > > >> > > > > > > > vds_on_boot. > > > >> > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > Let's talk f2f on Tuesday? > > > >> > > > > > > > > >> > > > > > I'd prefer to reach conclusions here, I'd like everyone to > > > >> > > > > > be > > > >> > > involved > > > >> > > > > in a > > > >> > > > > > root issue like this one. > > > >> > > > > > > > >> > > > > > > >> > > > What is the update frequency of this field? > > > >> > > > > > > >> > > > > > >> > > which field? > > > >> > > status? pending resources? on boot fields? > > > >> > > iinm, status is updated mostly by user actions, at least in > > > >> > > positive > > > >> > > scenarios, and not that often. > > > >> > > > > > >> > > > > > >> > > > > > > > > >> > > > > > > > > > >> > > > > > _______________________________________________ > > > >> > > > > > Devel mailing list > > > >> > > > > > Devel(a)ovirt.org > > > >> > > > > > http://lists.ovirt.org/mailman/listinfo/devel > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > > > > > > > > _______________________________________________ > > > > Devel mailing list > > > > Devel(a)ovirt.org > > > > http://lists.ovirt.org/mailman/listinfo/devel > > > > > > > > > > > > > >