30 Nov
2017
30 Nov
'17
2:26 p.m.
"Fabio M. Di Nitto" <fdinitto(a)redhat.com> writes:
Certainly not, but it begs the question that when these ABI versions can
be different. Actually, never. So why store it in each model instead
of simply compiling it into the module loader routine?
I have tried to write it into a module symbol, but there was a remapping
issue that had to be done per module.
This one works across the board without per module changes.
It´s a minor technicality IMHO.
You made me curious. Let me try to implement it...
OK, I rebased and squashed my branch somewhat. I'm pushing it as
modules2, we had some very similar ideas and some different ones!
--
Regards,
Feri
On 11/29/2017 2:52 PM, Ferenc Wágner wrote:
Consider the plugin packages as well:
libknet-1-crypto-nss ships /usr/lib/kronosnet-1/crypto_nss.so (ABI 1)
libknet-2-crypto-nss ships /usr/lib/kronosnet-2/crypto_nss.so (ABI 2)
libknet1_x has internal ABI 1, recommends libknet-1-crypto-nss
libknet1_y has internal ABI 2, recommends libknet-2-crypto-nss
Running application depends on libknet1, loads libknet.so.1.x into
memory. Upgrade libknet1 to version y, it pulls in the new package
libknet-2-crypto-nss. Running application can still load its ABI 1 NSS
module, because libknet-1-crypto-nss is still installed. One restarted,
it loads the new libknet.so.1.y, which can load the ABI 2 NSS module.
It's all seamless from the user PoV if libknet-1-crypto-nss isn't
removed too early.
The risky part is that libknet1_y may not pull libknet-2-crypto-nss
strongly enough. Debian installs recommended packages by default, but
not suggested ones. So suggested plugins may be lost during a minor
upgrade of libknet1, which doesn't sound very kind... I haven't thought
about metapackages yet.
All this complication does not arise if we just fail cleanly based on
version checks. Which may be good enough for corosync, but hypothetic
other cases may trigger module loading based on foreign network traffic,
if I understood correctly. Anyway, I can't see problems adding
directory versioning later if needed.
"Fabio M. Di Nitto"
<fabbione(a)fabbione.net> writes:
libknet1-1.0-x has internal API 1
libknet1-1.0-y has internal API 2
on update, the old dir would go away no matter what, unless you want to
do metapackages similar to kernel and keep them around.
IMHO, not worth it. On 11/29/2017 8:50 AM, Fabio M. Di Nitto wrote:
I think module directory versioning would be better, as it allows
coexistence of different module ABIs. That can help in your upgrade
scenario, if the (already loaded and running) core library is upgraded
and the modules with the old ABI version are left installed. On 11/28/2017 4:15 PM, Fabio M. Di Nitto wrote:
> 2) we need to define something like #define KNET_INTERNAL_CRYPTO_API_VER
> so that we can use that either to identify the path on disk where
> to load the modules (ex: pkglibdir/crypto/$VER/ or $VER/crypto) or
> checked at load time (or both). this should address point 4 below.
For now I added an internal API version check. I am not sure yet we need
to add also versioning on disk. It might be overkilling. What do you think? Speaking about
the version check: is it necessary to store the version
in the model description? It's a generic constant after all.
It is the easiest way to compare them and it´s only a uint8_t. Hardly a
resource issue ;) I tested doing build with version 1, copy the modules,
do a version 2
build, overwrite the modules, etc.. each module needs to know its own
version.
Sure, it's compiled into each module as well. My point is that all
models come from a single build of libknet.so, while the modules may
come from different builds.
>> 3) log_msg should not be exported in the
public API. This is a no-no
>> from me ;) Either pass the pointer to the function to the init of a
>> given module, or let´s find another way to report errors back from
>> the modules to main libknet.
>
> this is done in the current module branch.
Similarly to the above, is the function pointer worth storing in every
handle? I understand it's handy, because it's being passed around
anyway. My idea was writing it into another module symbol at load time
and defining the logging macros to use that when compiling modules.
Probably doesn't matter much, though.