Steven, you might be better off reading the Kafka stream into Cassandra and then doing the reads that way
/******************************************* Joe Stein Founder, Principal Consultant Big Data Open Source Security LLC http://www.stealth.ly Twitter: @allthingshadoop <http://www.twitter.com/allthingshadoop> ********************************************/ On Fri, Dec 6, 2013 at 11:04 AM, Steven Parkes <smpar...@smparkes.net>wrote: > I've figured I may end up doing something like this for reasons that sound > similar to what Otis describes. > > In my case, I may end up binary searching the log to match msg #s to dates > in the actual messages to find a particular time range of interest. > > So far it's just theory: I haven't gotten to the point of POC/sanity > checking it. But it sounds like it should work ... > > On Dec 6, 2013, at 7:56 AM, Joe Stein <joe.st...@stealth.ly> wrote: > > > You got the hamster on the wheel with this one :) > > > > So one way to make it work without any changes (or at least maybe very > > minor changes if at all) would possibly be to use your max offset and > fetch > > size this way > > > > M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 > > > > to get > > > > get last 3: M10 M11 M12 > > get last 3: M7 M8 M9 > > get last 3: M4 M5 M6 > > get last 3: M1 M2 M3 > > > > you would start at the end to get the highwaterk mark offset then you > would > > do > > > > maxOffset (since your at the end) - 3 with a fetch size of 3 and then > keep > > doing that > > > > so technically you are still looking forward but you are making the start > > position of your offset 3 behind > > > > so if the offset numbers matched your numbers (so offset of M1 is 1 and > > offset of M2 is 2) for this example... > > > > fetch((12-3),3) > > fetch((12-3-3),3) > > fetch(12-3-3-3),3) > > fetch(12-3-3-3),3) > > > > would produce > > > > M10 M11 M12 > > M7 M8 M9 > > M4 M5 M6 > > M1 M2 M3 > > > > This would mean no broker changes :) and just "tricking" the val > > fetchRequest = fetchRequestBuilder in your implementation of the > > SimpleConsumerShell.scala to "look backwards" but you are just moving the > > offset backwards from the end looking forward for your fetch size > > > > make sense? > > > > > > /******************************************* > > Joe Stein > > Founder, Principal Consultant > > Big Data Open Source Security LLC > > http://www.stealth.ly > > Twitter: @allthingshadoop <http://www.twitter.com/allthingshadoop> > > ********************************************/ > > > > > > On Fri, Dec 6, 2013 at 10:43 AM, Joe Stein <joe.st...@stealth.ly> wrote: > > > >> hmmm, I just realized that wouldn't work actually (starting at the end > is > >> fine)... the fetch size being taken in is still going to increment > forward > >> ... > >> > >> The KafkaApi would have to change because in readMessageSet it is doing > a > >> log.read of the FileMessageSet ... > >> > >> it should be possible though but not without changing the way the log is > >> read when getting the partition with ReplicaManager > >> > >> so let me take that all back and say... can't be done now but I think it > >> is feasible to be done with some broker modifications to read the log > >> differently... off the top of my head can't think of how to change the > >> log.read to-do this without digging more down into the code > >> > >> > >> > >> /******************************************* > >> Joe Stein > >> Founder, Principal Consultant > >> Big Data Open Source Security LLC > >> http://www.stealth.ly > >> Twitter: @allthingshadoop <http://www.twitter.com/allthingshadoop> > >> ********************************************/ > >> > >> > >> On Fri, Dec 6, 2013 at 10:26 AM, Joe Stein <joe.st...@stealth.ly> > wrote: > >> > >>> The fetch requests are very flexible to-do what you want with them. > >>> > >>> Take a look at SimpleConsumerShell.scala as a reference > >>> > >>> You could pass in OffsetRequest.LatestTime (-1) with a fetch size of 3 > >>> and then just keep doing that over and over again. > >>> > >>> I think that will do exactly what you are looking to-do. > >>> > >>> /******************************************* > >>> Joe Stein > >>> Founder, Principal Consultant > >>> Big Data Open Source Security LLC > >>> http://www.stealth.ly > >>> Twitter: @allthingshadoop <http://www.twitter.com/allthingshadoop> > >>> ********************************************/ > >>> > >>> > >>> On Fri, Dec 6, 2013 at 10:04 AM, Otis Gospodnetic < > >>> otis.gospodne...@gmail.com> wrote: > >>> > >>>> Hi, > >>>> > >>>> On Fri, Dec 6, 2013 at 9:38 AM, Tom Brown <tombrow...@gmail.com> > wrote: > >>>> > >>>>> Do you mean you want to start from the most recent data and go > >>>> backwards to > >>>>> the oldest data, or that you want to start with old data and consume > >>>>> forwards? > >>>>> > >>>> > >>>> Forwards is the "normal way". I'm looking for the "abnormal way", of > >>>> course ;) i.e. backwards. > >>>> If the following are the messages that came in, oldest to newest: > >>>> > >>>> M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 > >>>> > >>>> Then I'd love to be able to consume from the end, say in batches of 3, > >>>> like > >>>> this: > >>>> > >>>> get last 3: M10 M11 M12 > >>>> get last 3: M7 M8 M9 > >>>> get last 3: M4 M5 M6 > >>>> get last 3: M1 M2 M3 > >>>> > >>>> Of course, if messages keep coming in, then the new ones that arrive > >>>> would > >>>> get picked up first and, eventually, assuming Consumer can consume > faster > >>>> than messages are produced, all messages will get consumed. > >>>> > >>>> But the important/key part is that any new ones that arrive will get > >>>> picked > >>>> up first. > >>>> > >>>> If the former, it would be difficult or impossible in 0.7.x, but I > think > >>>>> doable in 0.8.x. (They added some sort of message index). If the > >>>> latter, > >>>>> that is easily accomplished in both versions. > >>>>> > >>>> > >>>> I'd love to know if that's really so and how to do it! > >>>> > >>>> We are looking to move to Kafka 0.8 in January and to add performance > >>>> monitoring for Kafka 0.8 to SPM (see > >>>> > >>>> > http://blog.sematext.com/2013/10/16/announcement-spm-performance-monitoring-for-kafka/ > >>>> ) > >>>> > >>>> Thanks, > >>>> Otis > >>>> -- > >>>> Performance Monitoring * Log Analytics * Search Analytics > >>>> Solr & Elasticsearch Support * http://sematext.com/ > >>>> > >>>> > >>>> > >>>>> On Friday, December 6, 2013, Otis Gospodnetic wrote: > >>>>> > >>>>>> Hi, > >>>>>> > >>>>>> Does Kafka offer a way to consume messages in batches, but "from the > >>>>> end"? > >>>>>> > >>>>>> This would be valuable to have in all systems where the most recent > >>>> data > >>>>> is > >>>>>> a lot more important than older data, such as performance metrics, > >>>> and > >>>>>> maybe even logs....maybe also trading/financial data, and such. > >>>>>> > >>>>>> Any chance of this sort of functionality ever making it into Kafka, > >>>> or is > >>>>>> this simply not implementable due to some underlying assumptions, or > >>>> data > >>>>>> structures, or ... ? > >>>>>> > >>>>>> Thanks, > >>>>>> Otis > >>>>>> -- > >>>>>> Performance Monitoring * Log Analytics * Search Analytics > >>>>>> Solr & Elasticsearch Support * http://sematext.com/ > >>>>>> > >>>>> > >>>> > >>> > >>> > >> > >
