The callouts about Oozie launcher and REST API calls are good ones -- I only 
ever interact with Oozie through the Oozie CLI. Is there any one place where 
all supported ways of interacting with Oozie server are documented?

Robert, does virtual IP (as suggested in the doc) solve the issue you speak of? 
The proxy in Oozie client could round robin between three Virtual IPs, and 
additional Oozie servers could be behind those Virtual IPs? That becomes an 
issue of integration then, rather than implementation on Oozie's part.

On 11/4/19, 8:42 AM, "Robert Kanter" <[email protected]> wrote:

    In addition to the reasons both Andras's mentioned, another reason is that
    the client doesn't need to know all of the Oozie server addresses.  While
    you can update the Oozie client config on your laptop if it worked that
    way, once the Oozie Launcher has started, you can't update the Oozie
    servers it knows about.  For example, suppose you had an Oozie launcher
    that ran for 3 days - you may have added/removed some Oozie servers in that
    time and now the Oozie Launcher's list of Oozie servers would be out of
    date.
    
    - Robert
    
    On Mon, Nov 4, 2019 at 4:01 AM Andras Piros <[email protected]> wrote:
    
    > Another point to add is that there are lots of users accessing Oozie not
    > via OozieCLI but via direct REST calls. As to my understanding the proxied
    > client story could work for OozieCLI only. In any case, it could make 
sense
    > to implement it that way.
    >
    > Regards,
    >
    > Andras
    >
    > On Mon, Nov 4, 2019 at 12:56 PM Andras Salamon
    > <[email protected]> wrote:
    >
    > > Hi,
    > >
    > > HA was added a long time ago, back in 2013. You can find the jira here:
    > > https://issues.apache.org/jira/browse/OOZIE-615. There is a design docs
    > > attached to the jira, which could be a good starting point. There is a
    > > section int it about the Load Balancer:
    > >
    > > "A loadbalancer, virtualIP, or DNSroundrobin: This would go in front of
    > the
    > > Oozie servers to (a) provide a single entry point for users so they 
don’t
    > > have to choose between, or even beaware of, multiple Oozie servers; and
    > (b)
    > > for callbacks from the JobTracker when a hadoop job is done (which can
    > only
    > > take a single address and simply choosing an arbitrary Oozie server 
could
    > > be a problem if that server goes down."
    > >
    > > Best,
    > > Sala
    > >
    > >
    > > On Sat, Nov 2, 2019 at 12:13 AM Poepping, Thomas
    > <[email protected]
    > > >
    > > wrote:
    > >
    > > > Hi Oozie development community!
    > > >
    > > > I am looking through documentation for the Oozie High Availability
    > > feature
    > > > (
    > > https://oozie.apache.org/docs/5.1.0/AG_Install.html#High_Availability_HA
    > > > ) and I am wondering why we need to set up virtual IP or load 
balancing
    > > for
    > > > callbacks from Resource Manager to Oozie? YARN follows a different
    > > > convention – including a proxied client that round robins between DNS
    > > names
    > > > configured in a list. Is there something blocking Oozie from doing the
    > > > same, or was this decision made because it also provides users with a
    > > > single endpoint to hit any of the oozie servers running?
    > > >
    > > > If there aren’t strong arguments against, I would like to open a JIRA
    > to
    > > > implement this. But first, please give me your comments!
    > > >
    > > > Thanks,
    > > > Tom
    > > >
    > >
    >
    

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