-Re: Hadoop streaming or pipes ..
Charles Earl 2012-04-05, 21:23
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.
On Apr 5, 2012, at 3:49 PM, Robert Evans <[EMAIL PROTECTED]> 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" <[EMAIL PROTECTED]> 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,