One solution is to only read up to (now - 1 second). If this is a public API where you want to guarantee full consistency (ie, if you have added a message to the queue, it will definitely appear to be there) you can instead delay requests for 1 second before reading up to the moment that the request was received.
In either of these approaches you can tune the time offset based on how closely synchronized you believe you can keep your clocks. The tradeoff of course, will be increased latency. On Wed, Jan 16, 2013 at 5:56 PM, Jason Tang <ares.t...@gmail.com> wrote: > Hi > > I am using Cassandra in a message bus solution, the major responsibility > of cassandra is recording the incoming requests for later consumming. > > One strategy is First in First out (FIFO), so I need to get the stored > request in reversed order. > > I use NTP to synchronize the system time for the nodes in the cluster. (4 > nodes). > > But the local time of each node are still have some inaccuracy, around 40 > ms. > > The consistency level is write all and read one, and replicate factor is 3. > > But here is the problem: > A request come to node One at local time PM 10:00:01.000 > B request come to node Two at local time PM 10:00:00.980 > > The correct order is A --> B > But the timestamp is B --> A > > So is there any way for Cassandra to keep the correct order for read > operation? (e.g. logical timestamp ?) > > Or Cassandra strong depence on time synchronization solution? > > BRs > //Tang > > > > >
