That would be totally awesome! Not sure if it helps here but for completeness: We completely "dumped" regular repairs - no matter if 'nodetool repair' or reaper - and run our own tool that does simply CL_ALL scraping over the whole cluster. It runs now for over a year in production and the only problem we encountered was that we got timeouts when scraping (too) large / tombstoned partitions. It turned out that the large partitions weren't even readable with CQL / cqlsh / DevCenter. So that wasn't a problem of the repair. It was rather a design problem. Storing data that can't be read doesn't make sense anyway.
What I can tell from our experience: - It works much more reliable than what we had before - also more reliable than reaper (state of 2016) - It runs totally smooth and much faster than regular repairs as it only streams what needs to be streamed - It's easily manageable, interruptible, resumable on a very fine-grained level. The only thing you need to do is to store state (KS/CF/Last Token) in a simple storage like redis - It works even pretty well when populating a empty node e.g. when changing RFs / bootstrapping DCs - You can easily control the cluster-load by tuning the concurrency of the scrape process I don't see a reason for us to ever go back to built-in repairs if they don't improve immensely. In many cases (especially with MVs) they are true resource killers. Just my 2 cent and experience. 2018-04-04 17:00 GMT+02:00 Ben Bromhead <b...@instaclustr.com>: > +1 to including the implementation in Cassandra itself. Makes managed > repair a first-class citizen, it nicely rounds out Cassandra's consistency > story and makes it 1000x more likely that repairs will get run. > > > > > On Wed, Apr 4, 2018 at 10:45 AM Jon Haddad <j...@jonhaddad.com> wrote: > > > Implementation details aside, I’m firmly in the “it would be nice of C* > > could take care of it” camp. Reaper is pretty damn easy to use and > people > > *still* don’t put it in prod. > > > > > > > On Apr 4, 2018, at 4:16 AM, Rahul Singh <rahul.xavier.si...@gmail.com> > > wrote: > > > > > > I understand the merits of both approaches. In working with other DBs > In > > the “old country” of SQL, we often had to write indexing sequences > manually > > for important tables. It was “built into the product” but in order to > > leverage the maximum benefits of indices we had to have different indices > > other than the clustered (physical index). The process still sucked. It’s > > never perfect. > > > > > > The JVM is already fraught with GC issues and putting another process > > being managed in the same heapspace is what I’m worried about. > Technically > > the process could be in the same binary but started as a side Car or in > the > > same main process. > > > > > > Consider a process called “cassandra-agent” that’s sitting around with > a > > scheduler based on config or a Cassandra table. Distributed in the same > > release. Shell / service scripts would start it. The end user knows it > only > > by examining the .sh files. This opens possibilities of including a GUI > > hosted in the same process without cluttering the core coolness of > > Cassandra. > > > > > > Best, > > > > > > -- > > > Rahul Singh > > > rahul.si...@anant.us > > > > > > Anant Corporation > > > > > > On Apr 4, 2018, 2:50 AM -0400, Dor Laor <d...@scylladb.com>, wrote: > > >> We at Scylla, implemented repair in a similar way to the Cassandra > > reaper. > > >> We do > > >> that using an external application, written in go that manages repair > > for > > >> multiple clusters > > >> and saves the data in an external Scylla cluster. The logic resembles > > the > > >> reaper one with > > >> some specific internal sharding optimizations and uses the Scylla rest > > api. > > >> > > >> However, I have doubts it's the ideal way. After playing a bit with > > >> CockroachDB, I realized > > >> it's super nice to have a single binary that repairs itself, provides > a > > GUI > > >> and is the core DB. > > >> > > >> Even while distributed, you can elect a leader node to manage the > > repair in > > >> a consistent > > >> way so the complexity can be reduced to a minimum. Repair can write > its > > >> status to the > > >> system tables and to provide an api for progress, rate control, etc. > > >> > > >> The big advantage for repair to embedded in the core is that there is > no > > >> need to expose > > >> internal state to the repair logic. So an external program doesn't > need > > to > > >> deal with different > > >> version of Cassandra, different repair capabilities of the core (such > as > > >> incremental on/off) > > >> and so forth. A good database should schedule its own repair, it knows > > >> whether the shreshold > > >> of hintedhandoff was cross or not, it knows whether nodes where > > replaced, > > >> etc, > > >> > > >> My 2 cents. Dor > > >> > > >> On Tue, Apr 3, 2018 at 11:13 PM, Dinesh Joshi < > > >> dinesh.jo...@yahoo.com.invalid> wrote: > > >> > > >>> Simon, > > >>> You could still do load aware repair outside of the main process by > > >>> reading Cassandra's metrics. > > >>> In general, I don't think the maintenance tasks necessarily need to > > live > > >>> in the main process. They could negatively impact the read / write > > path. > > >>> Unless strictly required by the serving path, it could live in a > > sidecar > > >>> process. There are multiple benefits including isolation, faster > > iteration, > > >>> loose coupling. For example - this would mean that the maintenance > > tasks > > >>> can have a different gc profile than the main process and it would be > > ok. > > >>> Today that is not the case. > > >>> The only issue I see is that the project does not provide an official > > >>> sidecar. Perhaps there should be one. We probably would've not had to > > have > > >>> this discussion ;) > > >>> Dinesh > > >>> > > >>> On Tuesday, April 3, 2018, 10:12:56 PM PDT, Qingcun Zhou < > > >>> zhouqing...@gmail.com> wrote: > > >>> > > >>> Repair has been a problem for us at Uber. In general I'm in favor of > > >>> including the scheduling logic in Cassandra daemon. It has the > benefit > > of > > >>> introducing something like load-aware repair, eg, only schedule > repair > > >>> while no ongoing compaction or traffic is low, etc. As proposed by > > others, > > >>> we can expose keyspace/table-level configurations so that users can > > opt-in. > > >>> Regarding the risk, yes there will be problems at the beginning but > in > > the > > >>> long run, users will appreciate that repair works out of the box, > just > > like > > >>> compaction. We have large Cassandra deployments and can work with > > Netflix > > >>> folks for intensive testing to boost user confidence. > > >>> > > >>> On the other hand, have we looked into how other NoSQL databases do > > repair? > > >>> Is there a side car process? > > >>> > > >>> > > >>> On Tue, Apr 3, 2018 at 9:21 PM, sankalp kohli < > kohlisank...@gmail.com > > >>> wrote: > > >>> > > >>>> Repair is critical for running C* and I agree with Roopa that it > > needs to > > >>>> be part of the offering. I think we should make it easy for new > users > > to > > >>>> run C*. > > >>>> > > >>>> Can we have a side car process which we can add to Apache Cassandra > > >>>> offering and we can put this repair their? I am also fine putting it > > in > > >>> C* > > >>>> if side car is more long term. > > >>>> > > >>>> On Tue, Apr 3, 2018 at 6:20 PM, Roopa Tangirala < > > >>>> rtangir...@netflix.com.invalid> wrote: > > >>>> > > >>>>> In seeing so many companies grapple with running repairs > successfully > > >>> in > > >>>>> production, and seeing the success of distributed scheduled repair > > here > > >>>> at > > >>>>> Netflix, I strongly believe that adding this to Cassandra would be > a > > >>>> great > > >>>>> addition to the database. I am hoping, we as a community will make > it > > >>>> easy > > >>>>> for teams to operate and run Cassandra by enhancing the core > product, > > >>> and > > >>>>> making the maintenances like repairs and compactions part of the > > >>> database > > >>>>> without external tooling. We can have an experimental flag for the > > >>>> feature > > >>>>> and only teams who are confident with the service can enable them, > > >>> while > > >>>>> others can fall back to default repairs. > > >>>>> > > >>>>> > > >>>>> *Regards,* > > >>>>> > > >>>>> *Roopa Tangirala* > > >>>>> > > >>>>> Engineering Manager CDE > > >>>>> > > >>>>> *(408) 438-3156 - mobile* > > >>>>> > > >>>>> > > >>>>> > > >>>>> > > >>>>> > > >>>>> On Tue, Apr 3, 2018 at 4:19 PM, Kenneth Brotman < > > >>>>> kenbrot...@yahoo.com.invalid> wrote: > > >>>>> > > >>>>>> Why not make it configurable? > > >>>>>> auto_manage_repair_consistancy: true (default: false) > > >>>>>> > > >>>>>> Then users can use the built in auto repair function that would be > > >>>>> created > > >>>>>> or continue to handle it as now. Default behavior would be "false" > > >>> so > > >>>>>> nothing changes on its own. Just wondering why not have that > option? > > >>>> It > > >>>>>> might accelerate progress as others have already suggested. > > >>>>>> > > >>>>>> Kenneth Brotman > > >>>>>> > > >>>>>> -----Original Message----- > > >>>>>> From: Nate McCall [mailto:zznat...@gmail.com] > > >>>>>> Sent: Tuesday, April 03, 2018 1:37 PM > > >>>>>> To: dev > > >>>>>> Subject: Re: Repair scheduling tools > > >>>>>> > > >>>>>> This document does a really good job of listing out some of the > > >>> issues > > >>>> of > > >>>>>> coordinating scheduling repair. Regardless of which camp you fall > > >>> into, > > >>>>> it > > >>>>>> is certainly worth a read. > > >>>>>> > > >>>>>> On Wed, Apr 4, 2018 at 8:10 AM, Joseph Lynch < > joe.e.ly...@gmail.com > > >>>>>> wrote: > > >>>>>>> I just want to say I think it would be great for our users if we > > >>>> moved > > >>>>>>> repair scheduling into Cassandra itself. The team here at Netflix > > >>> has > > >>>>>>> opened the ticket > > >>>>>>> <https://issues.apache.org/jira/browse/CASSANDRA-14346 > > >>>>>>> and have written a detailed design document > > >>>>>>> <https://docs.google.com/document/d/1RV4rOrG1gwlD5IljmrIq_ > > >>>> t45rz7H3xs9G > > >>>>>>> bFSEyGzEtM/edit#heading=h.iasguic42ger > > >>>>>>> that includes problem discussion and prior art if anyone wants to > > >>>>>>> contribute to that. We tried to fairly discuss existing > solutions, > > >>>>>>> what their drawbacks are, and a proposed solution. > > >>>>>>> > > >>>>>>> If we were to put this as part of the main Cassandra daemon, I > > >>> think > > >>>>>>> it should probably be marked experimental and of course be > > >>> something > > >>>>>>> that users opt into (table by table or cluster by cluster) with > the > > >>>>>>> understanding that it might not fully work out of the box the > first > > >>>>>>> time we ship it. We have to be willing to take risks but we also > > >>> have > > >>>>>>> to be honest with our users. It may help build confidence if a > few > > >>>>>>> major deployments use it (such as Netflix) and we are happy of > > >>> course > > >>>>>>> to provide that QA as best we can. > > >>>>>>> > > >>>>>>> -Joey > > >>>>>>> > > >>>>>>> On Tue, Apr 3, 2018 at 10:48 AM, Blake Eggleston > > >>>>>>> <beggles...@apple.com > > >>>>>>> wrote: > > >>>>>>> > > >>>>>>>> Hi dev@, > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> The question of the best way to schedule repairs came up on > > >>>>>>>> CASSANDRA-14346, and I thought it would be good to bring up the > > >>> idea > > >>>>>>>> of an external tool on the dev list. > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> Cassandra lacks any sort of tools for automating routine tasks > > >>> that > > >>>>>>>> are required for running clusters, specifically repair. Regular > > >>>>>>>> repair is a must for most clusters, like compaction. This means > > >>>> that, > > >>>>>>>> especially as far as eventual consistency is concerned, > Cassandra > > >>>>>>>> isn’t totally functional out of the box. Operators either need > to > > >>>>>>>> find a 3rd party solution or implement one themselves. Adding > this > > >>>> to > > >>>>>>>> Cassandra would make it easier to use. > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> Is this something we should be doing? If so, what should it look > > >>>> like? > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> Personally, I feel like this is a pretty big gap in the project > > >>> and > > >>>>>>>> would like to see an out of process tool offered. Ideally, > > >>> Cassandra > > >>>>>>>> would just take care of itself, but writing a distributed repair > > >>>>>>>> scheduler that you trust to run in production is a lot harder > than > > >>>>>>>> writing a single process management application that can > failover. > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> Any thoughts on this? > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> Thanks, > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> Blake > > >>>>>>>> > > >>>>>>>> > > >>>>>> > > >>>>>> ------------------------------------------------------------ > > >>> --------- > > >>>>>> To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org > > >>>>>> For additional commands, e-mail: dev-h...@cassandra.apache.org > > >>>>>> > > >>>>>> > > >>>>>> ------------------------------------------------------------ > > >>> --------- > > >>>>>> To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org > > >>>>>> For additional commands, e-mail: dev-h...@cassandra.apache.org > > >>>>>> > > >>>>>> > > >>>>> > > >>>> > > >>> > > >>> > > >>> > > >>> -- > > >>> Thank you & Best Regards, > > >>> --Simon (Qingcun) Zhou > > >>> > > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org > > For additional commands, e-mail: dev-h...@cassandra.apache.org > > > > -- > Ben Bromhead > CTO | Instaclustr <https://www.instaclustr.com/> > +1 650 284 9692 > Reliability at Scale > Cassandra, Spark, Elasticsearch on AWS, Azure, GCP and Softlayer >
