Re: Cassandra Data Stax java driver & Snappy Compression library
Thanks Janne... To clarify, Service S3 should not run in to any issues and I may choose to not fix the issue? Regards Sachin On Sat, Aug 1, 2015 at 11:50 PM, Janne Jalkanen wrote: > No, this just tells that your client (S3 using Datastax driver) cannot > communicate to the Cassandra cluster using a compressed protocol, since the > necessary libraries are missing on the client side. Servers will still > compress the data they receive when they write it to disk. > > In other words > > Client <- [uncompressed data] -> Server <- [compressed data] -> Disk. > > To fix, make sure that the Snappy libraries are in the classpath of your > S3 service application. As always, there’s no guarantee that this improves > your performance, since if your app is already CPU-heavy, the extra CPU > overhead of compression *may* be a problem. So measure :-) > > /Janne > > On 02 Aug 2015, at 02:17 , Sachin Nikam wrote: > > I am currently running a Cassandra 1.2 cluster. This cluster has 2 tables > i.e. > TableA and TableB. > > TableA is read and written to by Services S1 and S2 which use Astyanax > client library. > > TableB is read and written by Service S3 which uses the datastax java > driver 2.1. S3 also reads data from TableA. > > Both TableA and TableB are defined on the Cassandra nodes to use > SnappyCompressor. > > On start-up service, Service S3 throws the following WARNing messages. The > service is able to continue doing its normal operation thereafter > > ** > [main] WARN loggerClass=com.datastax.driver.core.FrameCompressor;Cannot > find Snappy class, you should make sure the Snappy library is in the > classpath if you intend to use it. Snappy compression will not be > available for the protocol. > *** > > > My questions are as follows-- > #1. Does the compression happen on the cassandra client side or within > cassandra server side itself? > #2. Does Service S3 need to pull in additional dependencies for Snappy > Compressions as mentioned here -- > > http://stackoverflow.com/questions/21784149/getting-cassandra-connection-error > #3. What happens without this additional library not being present on > class path of Service S3. Any data that S3 writes to TableB will not be > compressed? > Regards > Sachin > > >
linearizable consistency / Paxos ?
this link http://www.datastax.com/dev/blog/lightweight-transactions-in-cassandra-2-0 talks about linearizable consistency and lightweight transactions. but I am still not completely following it , just based on the article itself. the standard replication protocol in Cassandra does establish a total order (based on client TS, though that can be wrong/unfair), so in the case of the example mentioned in the article "if 2 people try to create the same account', yes if both of them just brute-force write, ultimately we will have one winner, who provided the higher TS (this is done consistently across all replicas). what really matters in the above situation is the ability to group the 2 operations "check existing account" and "create account" together and run them in an atomic way. so we need something like a 2-phase commit. I guess what is not clear from that article is , what is the fundamental difference between the standard replication protocol and Paxos that prevents us from implementing a 2-pc on top of the standard protocol? Thanks! yang
GossipingPropertyFileSnitch vs Ec2Snitch
Hi Based on * http://docs.datastax.com/en/cassandra/2.0/cassandra/architecture/architectureSnitchEC2_t.html * http://docs.datastax.com/en/cassandra/2.0/cassandra/architecture/architectureSnitchGossipPF_c.html What other benefits can Ec2Snitch provide in a single-region, multi-az AWS deployment besides automatically setting dc and rack for you as the snitch reads from EC2 metadata. Obviously there is a concern with what if there is something wrong with the metadata server... Thanks. John
Re: Scientific Paper of Gossip Protocol
Cassandra is based on Scuttle-butt protocol. Reference: Robbert van Renesse, Dan Mihai Dumitriu, Valient Gough, and Chris Thomas. Efficient reconciliation and flow control for anti-entropy protocols. In Proceedings of the 2nd Large Scale Distributed Systems and Middleware Workshop (LADIS '08) - bharat On Sun, Aug 2, 2015 at 10:31 AM, Thouraya TH wrote: > Hi all, > > Please, is there Scientific Paper of Gossip Protocol (algorithm) used by > cassandra > i need a paper published in a conference or in a journal. > > ? > > Thank you so much for help. > Kind Regards. >
Scientific Paper of Gossip Protocol
Hi all, Please, is there Scientific Paper of Gossip Protocol (algorithm) used by cassandra i need a paper published in a conference or in a journal. ? Thank you so much for help. Kind Regards.
