[PATCH] add documentation about backend naming for VMOD authors

[Geoff Simmons]

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On 11/01/2015 07:01 PM, Dridi Boukelmoune wrote:
> 
> We had sort-of started a discussion on IRC at some point about
> that, but there's no way AFAIK to enforce namespaces. This is why
> in this doc I suggest to back backends with a VMOD object, in order
> to get a vcl_name from the compiler and reuse it.

I should have pointed out that the doc-patch mentions the function
VCL_HasBackend(), which would come from another patch earlier in the
thread. So that part of the new docs should come if and when the code
patch is also added. VCL_HasBackend() tells you if a backend name is
already in use by a VCL.

The one object/one backend solution can help you with that as well,
but it depends on what you want your VMOD to do. I have a VMOD in the
works for creating new backends at runtime, and that won't work by
creating new objects for every backend, since objects can only be
created in vcl_init.

But it does have something similar to what you said, Dridi -- the VMOD
uses PRIV_VCL arguments to keep track of the backends that it created,
and then you can get the backends back (for req.backend_hint etc.)
with a function by_name("backend_name") that returns VCL_BACKEND.


Best,
Geoff
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