question Re: falcon replication - overlap in Archives of Support Questions (Read Only)

falcon replication - overlap

bigdata_superno — Wed, 28 Sep 2016 22:34:51 GMT

Trying to understand what happens if there is a scheduled Falcon replication that is running while another one starts? For example, if we have a hourly replication schedule and the one at T hour is still running, what happens if another one starts at T+1 hour?

Re: falcon replication - overlap

sramesh — Thu, 29 Sep 2016 03:41:34 GMT

Falcon supports feed replication and mirroring.

1> For Falcon feed replication, execution order is FIFO as this is based on feed/data avilability

2> For mirroring execution order is LAST_ONLY as replication job has to run only once to catch up

According to Oozie doc

execution: Specifies the execution order if multiple instances of the coordinator job have satisfied their execution criteria. Valid values are:
1> FIFO (oldest first) default 
2> LIFO (newest first)
3> ONLYLAST (discards all older materializations)

Re: falcon replication - overlap

bigdata_superno — Thu, 29 Sep 2016 04:16:42 GMT

@Sowmya Ramesh thanks for your response. Not sure I understood it correctly. For example, in the case of feed replication, if the first replication job is submitted at time T and is still in progress and another replication job submitted at T+1 hour, do you intend to say that both of them complete one after the other without any overlap, in a FIFO fashion?

All I am trying to understand is would my feed replication / mirroring job have any adverse impacts if their scheduling is not handled properly i.e. scheduled too frequently which would cause overlap while execution

Re: falcon replication - overlap

sramesh — Thu, 29 Sep 2016 04:48:28 GMT

Yes, there won't be any overlap.