question Re: What Happens if a Failed NameNode is Back On Again after the Standby Namenode became Active? in Archives of Support Questions (Read Only)

What Happens if a Failed NameNode is Back On Again after the Standby Namenode became Active?

javatariancoder — Tue, 04 Dec 2018 14:00:59 GMT

Hello Community,

Suppose the Following Scenario:

1) we have a HA hadoop Cluster

2) Active Namenode Fails for some reason (EX: POWEROFF)

3) Standby Namenode Becomes Active

4) The Failed Namenode becomes ON back again

the question is:

what happens then?

does the failed Namenode becomes a standby node, or what?

enlighten me please

thank you

akhilsnaik — Tue, 04 Dec 2018 14:38:58 GMT

also you can refer this jira which explains how HDFS handles the failover and choose the Namenode to be active. : https://issues.apache.org/jira/browse/HDFS-2185

Please accept this answer if it clarifies your doubt.

cloude — Tue, 04 Dec 2018 16:44:07 GMT

the question is:

what happens then?

does the failed Namenode becomes a standby node -- TRUE

akhilsnaik — Wed, 05 Dec 2018 02:14:00 GMT

Can you see if this answer helps you .Please accept this answer if it did.

javatariancoder — Wed, 05 Dec 2018 06:01:15 GMT

Thank you for your answer

I found the answer to my question after taking a look at the Failover_controller state machine diagram found in the Jira issue

it was not mentioned anywhere else

After all, The answer is TRUE

javatariancoder — Wed, 05 Dec 2018 06:04:12 GMT

Thank you for the answer,

the answer (TRUE) was expected actually, but I needed an official statement for it

I found it in the Jira issue mentioned above in the state machine diagram

Thank you anyway