Hi all ,
What is the expectation in the following scenario :
Namenode has 3 name dirs configured ..
1) Namenode upgrade starts - Upgrade fails after 1st directory is upgraded
(2nd and 3rd dir is left unchanged ..)
2) Namenode starts
3) Namenode shutdown and rollbacked
Are the new changes done meant to be visible ? With current implementation ,
after a rollback new changes are visible .. Is this expected ??
As per my observation , since Namenode is saving the latest image dir(the
upgraded 1st dir since checkpointtime is incremented during upgrade for this
dir) will be loaded and saved to all dirs during loadfsimage ..
But if a ROLLBACK is done , the 1st dir will be rolled back (the older copy
becomes current and its checkpointtime is now LESS than other dirs ..) and
others left behind since they dont contain previous .. Now during
loadfsimage , the 2nd dir will be selected since it has the highest
checkpoint time and saved to all dirs (including 1st ) .. Now due to this ,
the new changes b/w UPGRADE and ROLLBACK DELTA present in 2nd dir gets
reflected even after ROLLBACK ..
Is this expected ? I ask this since :
1) this is not the case with a SUCCESSFULL Upgrade/Rollback (New changes are
lost after rollback).. &
2) In Hadoop-702 (DFS Upgrade Proposal) , FSStateTransition7.htm says { r0.
if previous directory does not exist then fail rollback } , but it continues
in the current implementation ..
Regards ,
Sreehari
HUAWEI TECHNOLOGIES CO.,LTD. huawei_logo
Solitaire
Domlur
Bangalore
www.huawei.com
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