Alexey Serbin has posted comments on this change. Change subject: KUDU-1679 Propagate timestamps for scans ......................................................................
Patch Set 2: (1 comment) > I mention this yesterday, but it was pretty late and maybe you > didn't get a chance to read it. > A snapshot's timestamp is distinct from the timestamp that is > propagated. If you look at NewScanRequestPB > (https://github.com/cloudera/kudu/blob/master/src/kudu/tserver/tserver.proto#L209) > you can see that there is a snap_timestamp field and > propagated_timestamp field. > We already propagate the client's timestamp to the server (when we > set 'snap_timestamp' in NewScanRequestPB, what we're missing is > getting a 'propagated_timestamp' in ScanResponsePB and using that > to update the client's last known timestamp. > > The snap_timestamp in the ScanRequest/Response refers to the > timestamp of the scan itself. For instance the user can set this > arbitrarily in the past to do historic scans, but the > propagated_timestamp would still be the current value of the > servers clock. > I see how having a 'snap_timestamp' in the response might be > confusing, but it does refer to the scan's timestamp and not to the > timestamp that must be propagated. It's there because if the user > doesn't specify a timestamp for the scan the server chooses one > (based on the value obtained from the clock if after being updated > with the ScanRequest's propagated timestamp). The value is returned > on the response so that the client can continue the scan on another > tablet while using the same timestamp. Thank you for the explanation. For some reason, I confused the propagated timestamp and scan timestamp. Posted the updated patch. http://gerrit.cloudera.org:8080/#/c/5099/2//COMMIT_MSG Commit Message: Line 7: [c++client] propagating timestamp for scans > nit: can you put the JIRA in the first line of the commit message? eg KUDU- Done -- To view, visit http://gerrit.cloudera.org:8080/5099 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: comment Gerrit-Change-Id: I4d79024b088ea88fd194cabcb61e640f66326264 Gerrit-PatchSet: 2 Gerrit-Project: kudu Gerrit-Branch: master Gerrit-Owner: Alexey Serbin <[email protected]> Gerrit-Reviewer: Alexey Serbin <[email protected]> Gerrit-Reviewer: David Ribeiro Alves <[email protected]> Gerrit-Reviewer: Kudu Jenkins Gerrit-Reviewer: Todd Lipcon <[email protected]> Gerrit-HasComments: Yes
