I think the code is the only documentation. A Writable is just something that has a readFrom and a writeTo method, the contents of these methods can be essentially arbitrary.
Best, Andrew On Sun, Mar 23, 2014 at 7:43 PM, Dhaivat Pandya <dhaivatpan...@gmail.com>wrote: > Another question: is there some kind of documentation (other than the code) > that specifies the kind of serialization algorithm Writables use? I think I > may have to port the concept over to another language. > > Thanks, > > Dhaivat > > > On Sun, Mar 23, 2014 at 9:11 AM, Dhaivat Pandya <dhaivatpan...@gmail.com > >wrote: > > > Thank you very much, Andrew. > > > > > > On Sat, Mar 22, 2014 at 7:02 PM, Andrew Wang <andrew.w...@cloudera.com > >wrote: > > > >> Hi Dhaivat, > >> > >> Take a look at DatanodeRegistration and it's parent class DatanodeID. DR > >> is > >> a Writable, meaning it's a custom serialization format. Hadoop 2 uses > >> protobuf for the RPC serialization rather than writables (with the > >> exception of DN data transfer). > >> > >> > >> > https://github.com/apache/hadoop-common/blob/branch-1.2/src/hdfs/org/apache/hadoop/hdfs/server/protocol/DatanodeRegistration.java > >> > >> > https://github.com/apache/hadoop-common/blob/branch-1.2/src/hdfs/org/apache/hadoop/hdfs/protocol/DatanodeID.java > >> > >> Best, > >> Andrew > >> > >> > >> On Sat, Mar 22, 2014 at 1:16 PM, Dhaivat Pandya < > dhaivatpan...@gmail.com > >> >wrote: > >> > >> > Hi everyone, > >> > > >> > I'm currently working on an application that requires some important > >> > details about the DataNode registration (w/ NameNode) procedure. > >> > > >> > Specifically, I have understood (after Wireshark-ing and looking > through > >> > the Hadoop code) that the DataNode is registered with the NameNode > >> using a > >> > single packet which tells the NameNode where the DataNode is "located" > >> > (i.e. host and port). > >> > > >> > However, in this packet, I'm not clear as to what scheme is used to > >> > serialize the DataNode information. I am running Hadoop 1.2.1. Any > >> > information will be appreciated. > >> > > >> > Thank you, > >> > > >> > Dhaivat Pandya > >> > > >> > > > > >
