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From Dmitriy Setrakyan <dsetrak...@apache.org>
Subject Re: IEP-14: Ignite failures handling (Discussion)
Date Tue, 13 Mar 2018 23:24:27 GMT
On Tue, Mar 13, 2018 at 7:13 PM, Ivan Rakov <ivan.glukos@gmail.com> wrote:

> I just would like to add my +1 for "kill if standalone, stop if embedded"
> default option. My arguments:
>
> 1) Regarding "If Ignite hangs - it will likely be impossible to stop":
> Unfortunately, it's true that Ignite can hang during stop procedure.
> However, most of failures described under IEP-14 (storage IO exceptions,
> death of critical system worker thread, etc) normally shouldn't turn node
> into "impossible to stop" state. Turning into that state is a bug itself. I
> guess that we shouldn't choose system behavior on the basis of known bugs.


The whole discussion is about protecting against force-major issues,
including Ignite bugs. You are assuming that a user application will
somehow continue to function if an Ignite node is stopped. In most cases it
will just freeze itself and cause the rest of the application to hang.

Again, "kill+stop" is the most deterministic and the safest default
behavior. Try a graceful shutdown (which will make restart easier), and
then kill the process regardless.

Note that we are arguing about the default behavior. If a user does not
like this default, then this user can change it to another behavior.


> 2) User might want to handle Ignite node crash before shutting down the
> whole JVM - raise alert, close external resources, etc
>

Very unlikely, but if a user is this advanced, then this user can change
the default behavior. Most users will not even know how to configure such
custom shutdown behavior and would prefer an automatic kill.

3) IEP-14 document has important notes: "More than one Ignite node could be
> started in one JVM process" and "Different nodes in one JVM process could
> belong to different clusters". This is possible only in embedded mode. I
> think, we shouldn't shock user by sudden JVM halt (possibly, along with
> another healthy nodes) if there's a chance of successful node stop.
>

Has anyone actually seen a real example of that? I have not. This scenario
is extremely unlikely and should not define the default behavior. Again, if
a user is so advanced to come up with such a sophisticated deployment, then
the same user should be able to set different default behaviors for
different clusters.

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