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ZhaoYang commented on CASSANDRA-15907: -------------------------------------- {quote}If the number of stale results is very large (i.e. a "silent" replica exists in the vast majority of responses), won't those two approaches result in about the same performance profile? {quote} the second approach will execute RFP requests in two places: # at the beginning of 2nd phase, based on the collected outdated rows from 1st phase. These RFP requests can run in parallel and the number can be large. # at merge-listener, for additional rows requested by SRP. These RFP requests have to run in serial, but the number is usually small. > Operational Improvements & Hardening for Replica Filtering Protection > --------------------------------------------------------------------- > > Key: CASSANDRA-15907 > URL: https://issues.apache.org/jira/browse/CASSANDRA-15907 > Project: Cassandra > Issue Type: Improvement > Components: Consistency/Coordination, Feature/2i Index > Reporter: Caleb Rackliffe > Assignee: Caleb Rackliffe > Priority: Normal > Labels: 2i, memory > Fix For: 4.0-beta > > > CASSANDRA-8272 uses additional space on the heap to ensure correctness for 2i > and filtering queries at consistency levels above ONE/LOCAL_ONE. There are a > few things we should follow up on, however, to make life a bit easier for > operators and generally de-risk usage: > (Note: Line numbers are based on {{trunk}} as of > {{3cfe3c9f0dcf8ca8b25ad111800a21725bf152cb}}.) > *Minor Optimizations* > * {{ReplicaFilteringProtection:114}} - Given we size them up-front, we may be > able to use simple arrays instead of lists for {{rowsToFetch}} and > {{originalPartitions}}. Alternatively (or also), we may be able to null out > references in these two collections more aggressively. (ex. Using > {{ArrayList#set()}} instead of {{get()}} in {{queryProtectedPartitions()}}, > assuming we pass {{toFetch}} as an argument to {{querySourceOnKey()}}.) > * {{ReplicaFilteringProtection:323}} - We may be able to use > {{EncodingStats.merge()}} and remove the custom {{stats()}} method. > * {{DataResolver:111 & 228}} - Cache an instance of > {{UnaryOperator#identity()}} instead of creating one on the fly. > * {{ReplicaFilteringProtection:217}} - We may be able to scatter/gather > rather than serially querying every row that needs to be completed. This > isn't a clear win perhaps, given it targets the latency of single queries and > adds some complexity. (Certainly a decent candidate to kick even out of this > issue.) > *Documentation and Intelligibility* > * There are a few places (CHANGES.txt, tracing output in > {{ReplicaFilteringProtection}}, etc.) where we mention "replica-side > filtering protection" (which makes it seem like the coordinator doesn't > filter) rather than "replica filtering protection" (which sounds more like > what we actually do, which is protect ourselves against incorrect replica > filtering results). It's a minor fix, but would avoid confusion. > * The method call chain in {{DataResolver}} might be a bit simpler if we put > the {{repairedDataTracker}} in {{ResolveContext}}. > *Guardrails* > * As it stands, we don't have a way to enforce an upper bound on the memory > usage of {{ReplicaFilteringProtection}} which caches row responses from the > first round of requests. (Remember, these are later used to merged with the > second round of results to complete the data for filtering.) Operators will > likely need a way to protect themselves, i.e. simply fail queries if they hit > a particular threshold rather than GC nodes into oblivion. (Having control > over limits and page sizes doesn't quite get us there, because stale results > _expand_ the number of incomplete results we must cache.) The fun question is > how we do this, with the primary axes being scope (per-query, global, etc.) > and granularity (per-partition, per-row, per-cell, actual heap usage, etc.). > My starting disposition on the right trade-off between > performance/complexity and accuracy is having something along the lines of > cached rows per query. Prior art suggests this probably makes sense alongside > things like {{tombstone_failure_threshold}} in {{cassandra.yaml}}. -- This message was sent by Atlassian Jira (v8.3.4#803005) --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org For additional commands, e-mail: commits-h...@cassandra.apache.org