Why namenode logs into itself as well as job tracker?

[Foss User <fo...@gmail.com>]

I have a namenode and job tracker on two different machines.

I see that a namenode tries to do an ssh log into itself (name node),
job tracker as well as all slave machines.

However, the job tracker tries to do an ssh log into the slave
machines only. Why this difference in behavior? Could someone please
explain what is going on behind the scenes?

Re: Why namenode logs into itself as well as job tracker?

[Aaron Kimball <aa...@cloudera.com>]

If you're using the start-dfs.sh script, it's ssh'ing into every machine in
conf/masters to start a SecondaryNameNode instance. The NameNode itself is
started locally. It then ssh's into every machine in conf/slaves to start a
DataNode instance.

Similarly, the JT is started locally by start-mapred.sh. But it sshs to
every machine in conf/slaves to start a TaskTracker.

- Aaron

On Sat, Apr 4, 2009 at 6:36 AM, Foss User <fo...@gmail.com> wrote:

> I have a namenode and job tracker on two different machines.
>
> I see that a namenode tries to do an ssh log into itself (name node),
> job tracker as well as all slave machines.
>
> However, the job tracker tries to do an ssh log into the slave
> machines only. Why this difference in behavior? Could someone please
> explain what is going on behind the scenes?
>