FYI, there is some ongoing sort-of-related work going on in CASSANDRA-19534 <https://issues.apache.org/jira/browse/CASSANDRA-19534>
On Wed, Apr 10, 2024 at 6:35 PM Jaydeep Chovatia <chovatia.jayd...@gmail.com> wrote: > Just created an official CEP-41 > <https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-41+%28DRAFT%29+Apache+Cassandra+Unified+Rate+Limiter> > incorporating the feedback from this discussion. Feel free to let me know > if I may have missed some important feedback in this thread that is not > captured in the CEP-41. > > Jaydeep > > On Thu, Feb 22, 2024 at 11:36 AM Jaydeep Chovatia < > chovatia.jayd...@gmail.com> wrote: > >> Thanks, Josh. I will file an official CEP with all the details in a few >> days and update this thread with that CEP number. >> Thanks a lot everyone for providing valuable insights! >> >> Jaydeep >> >> On Thu, Feb 22, 2024 at 9:24 AM Josh McKenzie <jmcken...@apache.org> >> wrote: >> >>> Do folks think we should file an official CEP and take it there? >>> >>> +1 here. >>> >>> Synthesizing your gdoc, Caleb's work, and the feedback from this thread >>> into a draft seems like a solid next step. >>> >>> On Wed, Feb 7, 2024, at 12:31 PM, Jaydeep Chovatia wrote: >>> >>> I see a lot of great ideas being discussed or proposed in the past to >>> cover the most common rate limiter candidate use cases. Do folks think we >>> should file an official CEP and take it there? >>> >>> Jaydeep >>> >>> On Fri, Feb 2, 2024 at 8:30 AM Caleb Rackliffe <calebrackli...@gmail.com> >>> wrote: >>> >>> I just remembered the other day that I had done a quick writeup on the >>> state of compaction stress-related throttling in the project: >>> >>> >>> https://docs.google.com/document/d/1dfTEcKVidRKC1EWu3SO1kE1iVLMdaJ9uY1WMpS3P_hs/edit?usp=sharing >>> >>> I'm sure most of it is old news to the people on this thread, but I >>> figured I'd post it just in case :) >>> >>> On Tue, Jan 30, 2024 at 11:58 AM Josh McKenzie <jmcken...@apache.org> >>> wrote: >>> >>> >>> 2.) We should make sure the links between the "known" root causes of >>> cascading failures and the mechanisms we introduce to avoid them remain >>> very strong. >>> >>> Seems to me that our historical strategy was to address individual known >>> cases one-by-one rather than looking for a more holistic load-balancing and >>> load-shedding solution. While the engineer in me likes the elegance of a >>> broad, more-inclusive *actual SEDA-like* approach, the pragmatist in me >>> wonders how far we think we are today from a stable set-point. >>> >>> i.e. are we facing a handful of cases where nodes can still get pushed >>> over and then cascade that we can surgically address, or are we facing a >>> broader lack of back-pressure that rears its head in different domains >>> (client -> coordinator, coordinator -> replica, internode with other >>> operations, etc) at surprising times and should be considered more >>> holistically? >>> >>> On Tue, Jan 30, 2024, at 12:31 AM, Caleb Rackliffe wrote: >>> >>> I almost forgot CASSANDRA-15817, which introduced >>> reject_repair_compaction_threshold, which provides a mechanism to stop >>> repairs while compaction is underwater. >>> >>> On Jan 26, 2024, at 6:22 PM, Caleb Rackliffe <calebrackli...@gmail.com> >>> wrote: >>> >>> >>> Hey all, >>> >>> I'm a bit late to the discussion. I see that we've already discussed >>> CASSANDRA-15013 <https://issues.apache.org/jira/browse/CASSANDRA-15013> >>> and CASSANDRA-16663 >>> <https://issues.apache.org/jira/browse/CASSANDRA-16663> at least in >>> passing. Having written the latter, I'd be the first to admit it's a crude >>> tool, although it's been useful here and there, and provides a couple >>> primitives that may be useful for future work. As Scott mentions, while it >>> is configurable at runtime, it is not adaptive, although we did >>> make configuration easier in CASSANDRA-17423 >>> <https://issues.apache.org/jira/browse/CASSANDRA-17423>. It also is >>> global to the node, although we've lightly discussed some ideas around >>> making it more granular. (For example, keyspace-based limiting, or limiting >>> "domains" tagged by the client in requests, could be interesting.) It also >>> does not deal with inter-node traffic, of course. >>> >>> Something we've not yet mentioned (that does address internode traffic) >>> is CASSANDRA-17324 >>> <https://issues.apache.org/jira/browse/CASSANDRA-17324>, which I >>> proposed shortly after working on the native request limiter (and have just >>> not had much time to return to). The basic idea is this: >>> >>> When a node is struggling under the weight of a compaction backlog and >>> becomes a cause of increased read latency for clients, we have two safety >>> valves: >>> >>> >>> 1.) Disabling the native protocol server, which stops the node from >>> coordinating reads and writes. >>> 2.) Jacking up the severity on the node, which tells the dynamic snitch >>> to avoid the node for reads from other coordinators. >>> >>> >>> These are useful, but we don’t appear to have any mechanism that would >>> allow us to temporarily reject internode hint, batch, and mutation messages >>> that could further delay resolution of the compaction backlog. >>> >>> >>> Whether it's done as part of a larger framework or on its own, it still >>> feels like a good idea. >>> >>> Thinking in terms of opportunity costs here (i.e. where we spend our >>> finite engineering time to holistically improve the experience of operating >>> this database) is healthy, but we probably haven't reached the point of >>> diminishing returns on nodes being able to protect themselves from clients >>> and from other nodes. I would just keep in mind two things: >>> >>> 1.) The effectiveness of rate-limiting in the system (which includes the >>> database and all clients) as a whole necessarily decreases as we move from >>> the application to the lowest-level database internals. Limiting correctly >>> at the client will save more resources than limiting at the native protocol >>> server, and limiting correctly at the native protocol server will save more >>> resources than limiting after we've dispatched requests to some thread pool >>> for processing. >>> 2.) We should make sure the links between the "known" root causes of >>> cascading failures and the mechanisms we introduce to avoid them remain >>> very strong. >>> >>> In any case, I'd be happy to help out in any way I can as this moves >>> forward (especially as it relates to our past/current attempts to address >>> this problem space). >>> >>> >>> >>>
