[erlang-questions] Distributed Application Without Priority?

Ulf Wiger ulf@REDACTED
Thu Jun 20 20:51:14 CEST 2013

If you check the docs for application:load/2, it says:

"Nodes is a list of node names where the application may run, in priority from left to right. Node names can be grouped using tuples to indicate that they have the same priority. Example:

Nodes = [cp1@REDACTED, {cp2@REDACTED, cp3@REDACTED}]"

In the example above, cp2@REDACTED and cp3@REDACTED have the same priority.

Takeover happens either when explicitly ordered when a higher-priority node appears.

Ulf W

Ulf Wiger, Feuerlabs, Inc.

20 jun 2013 kl. 19:54 skrev "Phillips, Christopher" <Christopher.Phillips@REDACTED>:

>   We have a system currently that has two nodes that a distributed application runs across. We've talked about what it would take to make it run on both, but for now it's easier to just fail over when one node goes down.
>   We have no real need for priority in this. We really don't care which the app runs on, just that it's running somewhere. Put another way; I'd like to support failover, while preventing take over.
>   I, first, wondered if there was a mechanism that supported this; everything I see for distributed applications describes listing them in priority order, rather than without a priority. 
>   I can see at least one way I might achieve preventing takeover, but it seems like if it was unintentional it may have some unexpected side effects; namely, make it so node 1 lists node 2 as higher preference, and node 2 lists node 1 as higher preference, which would achieve, to my best understanding, what I want (a quick smoke test showed it working like I'd expect), but I'm not sure what risks it might carry with it. My second question is, does anyone know what issues this might cause if we tried running things this way?
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