Some further observation, 2014-06-19 1:40 GMT+01:00 Arcadius Ahouansou <arcad...@menelic.com>:
> > Hello Erick. > > On 17 June 2014 16:52, Erick Erickson <erickerick...@gmail.com> wrote: > >> The sticky parts of that solution (off the top of my head) are >> >> > assuring that the two masters have all the updates. How do you >> guarantee that the updates succeed and the two masters do, indeed, contain >> the exact same information? >> >> > Let's assume the simple case when the Solr DIH is being used to pull data > from a central RDBMS to each master every 15min. > In that case, both master should be in sync even if the index versions are > different. > A monitoring system could be used to periodically check doc count is > almost the same on both masters. > I don't understand the point and the "almost the same". We need the same docs, no space here for "almost" . To have this I suggest Master 02 to be actually a slave of master 01. In this way we are sure the indexes are aligned. > > > > There'd have to be logic to insure that when the switch was made, the >> entire index was replicated. How would the slave know which segments to >> replicate from the master? Especially since the segments would NOT be >> identical, the slaves would have to replicate the entire index... >> >> > > In the event of a switch-over, I would expect the slaves fetching the > whole/full index from master02 > In production, the monitoring system should also alert the support team. > > >> > What to do when the first master came back up? Which one should be the >> "one true source"? >> >> > > We have 2 options here: > - either stay on master02 until a human intervention (rest API reset or > restart of master02), or > - switch back to master01 automatically > > Why don't put behind a Virtual IP the current master ? the slave will not know who is fetching. In case of disaster we switch behind the Virtual IP the master01 with master02( that was already perfectly aligned as a repetitor) > > >> > The whole question of all the slaves knowing what master to ping is >> actually pretty ambiguous. What happens if slave 1 pings master1 and >> there's a temporary network glitch so it switches to master2. Meanwhile, >> due to timing, slave2 thinks master1 is still online. How to detect/track >> this? >> >> > I thought about this situation and I must admit that it's a tricky one. > We should offer the option to configure the slaves to switch let's say > only after N failures (configurable) or after retrying for a configurable > period of time. > > > >> When you start to spin these scenarios, you start needing some kind of >> cluster state accessible to all slaves, and then you start thinking >> about ZooKeeper and you're swiftly back to SolrCloud. >> >> The thinking in traditional Solr M/S situations avoids having two >> masters, if a master dies you "promote" one of the slaves to be the >> new master. The tricky bit here is to re-index data from before the >> time the old master died to the new master. >> >> So far, that's been "good enough" for M/S setups, and then SolrCloud >> came along so I suspect not much effort would be put into something >> like what you suggest; the effort should be towards hardening >> SolrCloud... >> >> > > Yes, I do understand that SolrCloud is the future. > However, removing this singlePointOfFailure from the traditional > master-slave deployment model would not require a lot of effort IMHO and > would give huge benefit in term of choice. > > The other question is: How many sites are on SolrCloud? How many are still > on master-slave? > > Thank you very much. > > Arcadius. > > > > > >> Best, >> Erick >> >> On Tue, Jun 17, 2014 at 6:54 AM, Alessandro Benedetti >> <benedetti.ale...@gmail.com> wrote: >> > Hello Arcadius, >> > why not simple moving to SolrCloud that already addresses fault >> tolerance >> > and high availability ? >> > Simply imagine a configuration of : >> > 1 shard, factor of replciation 3. >> > And you have even a better scenario than 2 masters and 1 slave. >> > >> > Cheers >> > >> > >> > 2014-06-17 14:43 GMT+01:00 Arcadius Ahouansou <arcad...@menelic.com>: >> > >> >> Hello. >> >> >> >> >> >> SolrCloud has been out for a while now. >> >> >> >> However, there are still many installations running Solr4 in the >> >> traditional master-slave setup. >> >> >> >> >> >> Currently, the Solr Master is the single point of failure of most >> >> master-slave deployment. >> >> >> >> This could be easily addressed by having : >> >> >> >> >> >> a- 2 independents Solr Masters running side-by-side and being fed >> >> simultaneously, >> >> >> >> b- all slaves configured with masterUrl=masterUrl01,masterUrl02 (needs >> to >> >> be implemented) >> >> >> >> c- by default, masterUrl01 will be used by all slaves. >> >> >> >> d- When the slaves catch an exception (like NoRouteToHostException or >> >> ConnectionTimedOutException etc), they will retry a couple of times >> before >> >> switching to using masterUrl02. >> >> >> >> >> >> I suppose you have thought about this issue before. >> >> >> >> So I would like to know whether there are issues with such a simple >> >> solution. >> >> >> >> This could also help deploy Solr across 2 different data-centers. >> >> >> >> >> >> Thank you very much. >> >> >> >> >> >> Arcadius. >> >> >> >> >> > >> > >> > >> > -- >> > -------------------------- >> > >> > Benedetti Alessandro >> > Visiting card : http://about.me/alessandro_benedetti >> > >> > "Tyger, tyger burning bright >> > In the forests of the night, >> > What immortal hand or eye >> > Could frame thy fearful symmetry?" >> > >> > William Blake - Songs of Experience -1794 England >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org >> For additional commands, e-mail: dev-h...@lucene.apache.org >> >> > > > -- > Arcadius Ahouansou > Menelic Ltd | Information is Power > M: 07908761999 > W: www.menelic.com > --- > -- -------------------------- Benedetti Alessandro Visiting card : http://about.me/alessandro_benedetti "Tyger, tyger burning bright In the forests of the night, What immortal hand or eye Could frame thy fearful symmetry?" William Blake - Songs of Experience -1794 England
