I thought you just wanted to test how big delay you have, that's why I suggested trace.
Your best option is to write with EACH_QUORUM as Alain said. That way you will get a response when the write is successful on all dcs. The downside is that the request will fail if one dc is down. As usual it's up to you to decide if that's acceptable or not. You could follow up with a LOCAL_QUORUM request if the EACH_QUORUM fails and rely on hints and repair to get consistency eventually. -- SIMON FONTANA OSCARSSON Software Developer Ericsson Ölandsgatan 1 37133 Karlskrona, Sweden simon.fontana.oscars...@ericsson.com www.ericsson.com On tis, 2018-07-10 at 16:32 +0000, Saladi Naidu wrote: > Simon, > Trace would be significant burden on the cluster and it has to be on all the > time. I am trying to find a way to know when a row is written on demand > basis, is there a way to determine that? > > Naidu Saladi > > > On Tuesday, July 10, 2018 2:24 AM, Simon Fontana Oscarsson > <simon.fontana.oscars...@ericsson.com> wrote: > > > Have you tried trace? > -- > SIMON FONTANA OSCARSSON > Software Developer > > Ericsson > Ölandsgatan 1 > 37133 Karlskrona, Sweden > simon.fontana.oscars...@ericsson.com > www.ericsson.com > > On mån, 2018-07-09 at 19:30 +0000, Saladi Naidu wrote: > > Cassandra is an eventual consistent DB, how to find when a row is actually > > written in multi DC environment? Here is the problem I am trying to solve > > > > - I have multi DC (3 DC's) Cassandra cluster/ring - One of the application > > wrote a row to DC1(using Local Quorum) and within span of 50 ms, it tried > > to read same row from DC2 and could not find > the > > row. Our both DC's have sub milli second latency at network level, usually > > <2 ms. We promised 20 ms consistency. In this case Application could not > > find the row in DC2 in 50 ms > > > > I tried to use "select WRITETIME(authorizations_json) from > > token_authorizations where ...." to find when the Row is written in each > > DC, but both DC's returned same Timestamp. After further > research > > I found that Client V3 onwards Timestamp is supplied at Client level so > > WRITETIME does not help > > "https://docs.datastax.com/en/developer/java-driver/3.4/manual/query_timestamps/"; > > > > So how to determine when the row is actually written in each DC? > > > > > > Naidu Saladi > >
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