| Posted | Nick | Remark | |
|---|---|---|---|
| #openstack-nova - 2019-10-30 | |||
| 20:52:21 | dansmith | efried: asking because I think I've seen some notes from you around this code in the past, | |
| 20:52:41 | dansmith | but do you have strong opinions on what we should do if we have, say, three glance endpoints and we get an error from one trying to do something? | |
| 20:52:57 | dansmith | looks like we round-robin the available endpoints, but don't move onto the next one after a failure | |
| 20:52:57 | efried | dansmith: we should not have three glance endpoints | |
| 20:53:09 | efried | unless you mean three interfaces | |
| 20:53:20 | dansmith | efried: three urls | |
| 20:53:23 | efried | f, did we not get rid of that api_servers thing yet? | |
| 20:53:25 | efried | stand by | |
| 20:53:35 | dansmith | no, the round-robin-ing you mean? that's still there | |
| 20:54:10 | dansmith | I honestly thought that we had pushed responsibility for that down into the glance client, but ... the round-robin stuff is there | |
| 20:54:12 | efried | omg we haven't even deprecated it yet! | |
| 20:54:22 | efried | we should do that. | |
| 20:54:37 | dansmith | efried: use more words.. what are the people currently using that supposed to do? | |
| 20:54:55 | efried | sorry | |
| 20:54:56 | efried | okay | |
| 20:55:27 | efried | people using api_servers were theoretically stuffing multiple endpoints in there, and then they were responsible for making sure all of those endpoints pointed to the same images. | |
| 20:55:37 | dansmith | right | |
| 20:55:41 | efried | nova would, on a given call, pick "the next one" and use it. | |
| 20:56:00 | efried | afaik nova never had any logic to, say, "try the next one" if one failed. | |
| 20:56:13 | dansmith | right, it doesn't, but if we can have multiples we should, but.. go on | |
| 20:56:18 | efried | Because nova doesn't keep track of how many there are. It just loads them up and cycles over them. | |
| 20:56:40 | efried | so if we had only one, we still "cycle" over just the one. | |
| 20:56:50 | efried | and if we tried to add a "try next" thing, we would just end up trying... the same one. | |
| 20:57:28 | dansmith | well, all we'd have to do is retry N-1 times for an endpoint count of N and then we'd hit them all and not dupe one or more | |
| 20:57:29 | efried | if api_servers was a thing we still wanted people to use, I could see enhancing our logic to do that properly - keep track of how many there are and, on certain classes of error, try the next and so on until we succeed or come full circle | |
| 20:57:31 | efried | but | |
| 20:57:39 | efried | we don't want people to use api_servers. | |
| 20:57:47 | dansmith | and that is because why? | |
| 20:57:49 | efried | They should use a single endpoint that's a front for a load balancer | |
| 20:58:02 | efried | and use standard ksa options like every other service | |
| 20:58:25 | dansmith | yeah, so the problem there is that you have to have a HA LB for that | |
| 20:59:04 | dansmith | cloud client software needs to handle failures like this to be robust, I'm not sure why nova shouldn't | |
| 20:59:11 | efried | I thought there was a project that did that for you | |
| 20:59:26 | efried | do we try to HA other things? cinder, keystone, neutron...? | |
| 20:59:33 | efried | (trick question) | |
| 20:59:52 | dansmith | well, glance and keystone would be much easier to retry than the others | |
| 20:59:59 | smcginnis | Not the API, but cinder services can be run active/active. | |
| 21:00:22 | smcginnis | And I've seen people use the active/passive pacemaker setup for things too. | |
| 21:00:29 | dansmith | yeah | |
| 21:00:31 | efried | smcginnis: behind a single catalog endpoint tho? | |
| 21:00:36 | smcginnis | Yeah | |
| 21:00:39 | efried | melwitt: would you mind giving this another look? https://review.opendev.org/#/c/615704/ | |
| 21:00:52 | dansmith | efried: well, point is, if you're going to deprecate it, I'd appreciate you getting that patch up so I can point the people I'm talking to about it | |
| 21:01:13 | dansmith | efried: I remember you talking about this a while ago, had kinda assumed it had already happened | |
| 21:01:32 | efried | dansmith: are you playing devil's advocate or do you really think nova should be responsible for load balancing glance? | |
| 21:01:34 | dansmith | tripleo is using api_servers, so they're going to need some notice | |
| 21:02:05 | dansmith | efried: not load balancing, but being able to have multiple endpoints and find one that works, yeah | |
| 21:02:33 | efried | yeah, "everyone" is probably still using api_servers, because we only added the standard ksa stuff in, I think, queens. | |
| 21:02:41 | dansmith | having to have a floating VIP and HA'ing services behind that VIP for everything really sucks | |
| 21:02:59 | efried | is tripleo using multiple endpoints to api_servers? | |
| 21:03:12 | dansmith | efried: just to be clear, "the ksa stuff" doesn't imply anything about multiple endpoints right? | |
| 21:03:15 | dansmith | efried: they are | |
| 21:03:19 | melwitt | efried: whoa, that is old. I can look at it again once I figure out what it's about again | |
| 21:03:37 | dansmith | efried: for glance, but we don't do the failover stuff, so not really for much gain | |
| 21:03:38 | efried | melwitt: thanks, I got a nudge from a downstream (not $employer) who needs it. | |
| 21:03:47 | melwitt | ack | |
| 21:04:02 | efried | dansmith: right, the way nova handles it really isn't HA-ish, it's more load-balance-ish. | |
| 21:04:29 | dansmith | efried: currently, right | |
| 21:04:51 | efried | dansmith: and no, "the ksa stuff" doesn't have anything for mulitiple endpoints... I don't think. (Can you put multiple endpoints in the service catalog?) | |
| 21:05:25 | dansmith | gah | |
| 21:05:30 | efried | dansmith: I can tell you this, cutting over to sdk to talk to glance, api_servers will have to be gone first. | |
| 21:05:46 | dansmith | brb | |
| 21:06:34 | dansmith | efried: I dunno about the service catalog, probably not | |
| 21:06:43 | dansmith | not saying that's a good thing, but.. :) | |
| 21:07:10 | dansmith | efried: okay so, can you put up a patch to deprecate it real quick so I can point people to it? | |
| 21:07:17 | efried | I'm going to have to nail down mordred for the more philosophical aspects of this. | |
| 21:07:20 | dansmith | efried: -W it if you want for completeness and comments or something | |
| 21:07:37 | efried | I can do that, yeah, though now you've got me doubting if we *should*. | |
| 21:07:38 | dansmith | efried: ack, we can blame lots of stuff on him like this | |
| 21:07:47 | dansmith | efried: that's fine, a place to collect feedback | |
| 21:07:50 | efried | ... | |
| 21:08:09 | dansmith | efried: the tripleo people can go voice their hate there if they want, or they may say "meh, okay, we can VIP this too" I honestly don't know | |
| 21:08:20 | efried | cool | |
| 21:08:39 | dansmith | efried: can you do that, like, uh, quickly so I can reply to someone quickly? :D | |
| 21:08:47 | efried | on it rn | |
| 21:08:52 | dansmith | spanks. | |
| 21:08:56 | efried | if people would stop bugging me in IRC. | |
| 21:12:57 | efried | dansmith: while you're waiting, I found this (search for api_servers) http://specs.openstack.org/openstack/nova-specs/specs/queens/implemented/use-ksa-adapter-for-endpoints.html#proposed-change | |
| 21:13:47 | dansmith | "The exception is [glance]api_servers, which will continue to be supported." | |
| 21:14:51 | dansmith | I wonder if "valid_interfaces" is an arbitrary list, such that you could have internal1, internal2, internal3? | |
| 21:15:48 | openstackgerrit | Joshua Cornutt proposed openstack/nova master: Moving get_hash_str() from md5 to sha-256 https://review.opendev.org/615704 | |
| 21:16:20 | dansmith | I also don't know how LBs (or HAproxy) handle a failed http session post-request.. meaning if I do a GET against glance and then the connection is reset after I've sent the GET, does the LB retry and re-play that against the next server? | |
| 21:16:24 | mriedem | dansmith: i think it might be, we've had to dig into the ksa code a few times to answer that | |
| 21:16:44 | dansmith | I'd kindof doubt it.. figure it'd fail the client, mark the server, next request doesn't include the bad server | |
| 21:16:56 | dansmith | which means if we don't retry we propagate the failure up | |
| 21:17:18 | dansmith | which is fine in the trivial case, but not so much when we're making multiple calls as part of a complex operation, like against cinder or neutron | |
| 21:17:39 | dansmith | mriedem: might be what, arbitrary? | |
| 21:17:45 | dansmith | or might be constrained? | |
| 21:18:32 | dansmith | based on the description in that spec, though, it tries them in order, so you'd hammer internal1 until it fails, and then try internal2, it sounds like | |
| 21:18:37 | dansmith | which wouldn't be what you'd want really | |
| 21:21:26 | openstackgerrit | Eric Fried proposed openstack/nova master: Deprecate [glance]api_servers https://review.opendev.org/692227 | |
| 21:21:28 | mriedem | dansmith: i think valid_interfaces is arbitrary but i've had to look this up multiple times in the ksa code | |
| 21:21:28 | efried | dansmith: ^ | |
| 21:21:38 | dansmith | efried: thanks | |
| 21:21:50 | efried | dansmith: no, valid_interfaces is public/private/internal only | |
| 21:21:59 | efried | I think they can have 'URL' suffixes for legacy reasons | |
| 21:22:01 | mriedem | also, on that note in the spec for api_servers, i want to say the godaddy or smorrison made a point that they still really needed that when the spec was being reviewed | |
| 21:22:48 | dansmith | mriedem: yeah, I *think* people are going to be quite unhappy about it, but we'll see | |
| 21:22:56 | mriedem | might have been in the ML, i don't see it in review comments | |
| 21:22:59 | efried | "really needed" meaning it was easier for us to continue to support it than it was for them to stop relying on our shoddy load balancing hack | |