Also bear in mind that there is a kind of detour involved, in the sense that a pipes map must send key,value data back to the Java process and then to reduce (more or less). I think that the Hadoop C Extension (HCE, there is a patch) is supposed to be faster. Would be interested to know if the community has any experience with HCE performance. C
On Apr 5, 2012, at 3:49 PM, Robert Evans <ev...@yahoo-inc.com> wrote: > Both streaming and pipes do very similar things. They will fork/exec a > separate process that is running whatever you want it to run. The JVM that > is running hadoop then communicates with this process to send the data over > and get the processing results back. The difference between streaming and > pipes is that streaming uses stdin/stdout for this communication so > preexisting processing like grep, sed and awk can be used here. Pipes uses a > custom protocol with a C++ library to communicate. The C++ library is tagged > with SWIG compatible data so that it can be wrapped to have APIs in other > languages like python or perl. > > I am not sure what the performance difference is between the two, but in my > own work I have seen a significant performance penalty from using either of > them, because there is a somewhat large overhead of sending all of the data > out to a separate process just to read it back in again. > > --Bobby Evans > > > On 4/5/12 1:54 PM, "Mark question" <markq2...@gmail.com> wrote: > > Hi guys, > quick question: > Are there any performance gains from hadoop streaming or pipes over > Java? From what I've read, it's only to ease testing by using your favorite > language. So I guess it is eventually translated to bytecode then executed. > Is that true? > > Thank you, > Mark >
