These questions are best fit for the whole hdfs-dev@ group, which am
adding while responding back.
You're correct that the local node being not chosen, a random node on
the same rack as the writer may be tried. However, if the writer node
itself had no local DN in the first place, a completely random node
across any rack may be selected.
This is visible at
On Thu, Apr 4, 2013 at 12:53 AM, Mei Long <[EMAIL PROTECTED]> wrote:
> Hi Harsh,
> I found your post on JIRA regarding the comments. I find them very confusing
> as well. I'm trying to figure out the following comment:
> * the 1st replica is placed on the local machine,
> * otherwise a random datanode.
> Do you know when it says "otherwise a random datanode," does it mean any
> random datanode anywhere on the network or a random datanode on the same
> rack as the local machine? I've been looking at the code for an hour and I'm
> getting more confused with the comment and code in chooseLocalNode()
> /* choose <i>localMachine</i> as the target.
> * if <i>localMachine</i> is not availabe,
> * choose a node on the same rack
> * @return the choosen node
> Your help is much appreciated!