[PATCH] add documentation about backend naming for VMOD authors
phk at phk.freebsd.dk
Mon Nov 2 13:37:23 CET 2015
In message <CABoVN9Ch55NOui_23_10x0Sr4Swm_cSi91xiO9aYGLx7ppBM6g at mail.gmail.com>, Dridi Bouke
>> * All "struct director" (= VCL_BACKEND) have a "vcl_name" which can
>> be queried from VCL. VMODs are responsible for doing something
>> sensible here.
>> * struct director without a struct backend do not appear in CLI/VSM
>> unless the VMOD implements all the stuff for this.
>Sounds good, though I don't know how to implement it.
It would have to be a very magical case before it *should* be
>> * struct director with a struct backend, defined in VCL is always
>> in CLI/VSM, and the vcl_name is the name from the VCL namespace.
>Sounds good, and for static backends defined in plain native vcl,
>backend.display_name == vcl.loaded_name + "." + director.vcl_name
*All* backend names has the from "$VCL.something"
>> * struct director with a struct backend, created by VMOD, may or
>> may not be in CLI/VSM, at the VMODs discretion.
>They are currently always in the CLI/VSM, and this is controlled by
>the VCL temperature changes. But I think a struct director with a
>struct backend should always show up in the CLI/VSM.
It probably should *almost* always show up, but there are valid
schenarios where a struct backend is good for a single request
and I can see why you wouldn't want to clutter CLI/VSM with that.
>> * If it is in CLI/VSM, the VRT() used to register it there may
>> modify the vcl_name to make sure it is globally unique.
>> (In practice: vcl-unique, because the namespace is $VCL.$BACKEND)
>Since the CLI/VSM only show backends (not director) that would be the
>backend's display_name. That is the part I'm not comfortable with, for
I understand that, but I think the alternative, failing backend creation
unpredictably (as seen from the VMOD) is worse.
>> * If the VMOD ensures there are no duplicate vcl_names in the
>> first place, the vcl_name will not be touched.
>The VMOD can enforce proper uniqueness, but can't prevent against name
>collisions from other VMODs.
... which is why the VRT function will have to step in.
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