David Ribeiro Alves has posted comments on this change. ( http://gerrit.cloudera.org:8080/8823 )
Change subject: KUDU-1704: add c++ client support for READ_YOUR_WRITES mode ...................................................................... Patch Set 10: (1 comment) http://gerrit.cloudera.org:8080/#/c/8823/10/src/kudu/client/scan_token-internal.cc File src/kudu/client/scan_token-internal.cc: http://gerrit.cloudera.org:8080/#/c/8823/10/src/kudu/client/scan_token-internal.cc@186 PS10, Line 186: client->data_->UpdateLatestObservedTimestamp(message.propagated_timestamp()); > Right, so KuduScanner::Open is called after this, and at that point it grab RYW with scan tokens is a bit of a fuzzy concept, since RYW is by definition local and scan tokens are by definition multi client. If I understand the suggestion, the point is that to get RYW in the point of view of the scan token emitter, we could safely ignore the scan token's receiver client's internal last propagated timestamp, which might be more recent. I think things get murky here a bit, since RYW with scan tokens are murky. I don't think it would necessarily be wrong to do that, but I think it makes reasoning about timestamps and how they get propagated a bit harder if we have two ways to choose the lower bound for the RYW scan. Moreover, in practice, I suspect it's very rarely the case that an active client is permanently being written to and read from (using scan tokens). My suggestion is to keep the path simple and the same as for the local scans. Maybe note somewhere that is a possible optimization if we ever notice scan token RYW reads stalling. -- To view, visit http://gerrit.cloudera.org:8080/8823 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: kudu Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: I34214245a78aed172a28fbdb395ff5bccd0fc0e1 Gerrit-Change-Number: 8823 Gerrit-PatchSet: 10 Gerrit-Owner: Hao Hao <hao....@cloudera.com> Gerrit-Reviewer: Alex Rodoni <arod...@cloudera.com> Gerrit-Reviewer: Dan Burkert <danburk...@apache.org> Gerrit-Reviewer: David Ribeiro Alves <davidral...@gmail.com> Gerrit-Reviewer: Hao Hao <hao....@cloudera.com> Gerrit-Reviewer: Kudu Jenkins Gerrit-Reviewer: Mike Percy <mpe...@apache.org> Gerrit-Reviewer: Tidy Bot Gerrit-Comment-Date: Fri, 02 Mar 2018 23:01:02 +0000 Gerrit-HasComments: Yes
