Assertion failure in VCL_DelBackend()

[Geoff Simmons]

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On 11/16/2015 10:55 AM, Poul-Henning Kamp wrote:
> 
> One of my background-tasks is to put the "hands-off!" items in 
> clearly marked #include files.

OK

> It's monday morning. [...]

All good. I can go with what's possible at the moment. Get well.

> But what I will say, is that we have a general object-lifetime 
> issue, which so far is related to both VMOD_PRIV's and backends, 
> and it is complicated.
> 
> One example is:
> 
> if (foomod.get_me_a_new_backend() == backend_1) { // do something 
> }
> 
> How long does that backend live ?
> 
> Who decides ? - and how ?

FWIW, the VMODs I have in mind are all based around the idea that
backends are owned by VCL, which defines their lifetime, unless you
explicitly delete them before the VCL is discarded.

(Now that you mention it, though, it would be quite useful for our use
case to let them live on until the child process dies ...)

> My current thinking is what I outlined last week(?) about
> VMOD_PRIV, that VMODs will have to become explicit about this.
> 
> If we do that and make backends (ie: directors) VMOD_PRIV's, then a
> VMOD would be able to create a backend and mark it for deletion 
> when the transaction dies, and have it happen automatically.

Well OK, but is there really a use case for backends with anything
shorter than PRIV_VCL lifetime? Backends that live and die during a
task or a top request ... that sounds pretty far out to me. And I
can't even picture what PRIV_CALL for a backend would mean.


Best,
Geoff
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