Hey Alan,
I do think "let user decide" is actually very relevant and important in this
context.
Some users (e.g us), like to keep the entire set (Core + Plugins + Config) as
one unit and deploy/manage them together.
While it may not be flexible enough to be able to update a plugin at a time,
there are several benefits to this approach (for e.g integration tests, we have
plugins that are owned by multiple partner teams and we simply don't want to
update those plugins individually without ensuring each version of it gels well
with the rest of the bundle).
But, we could on the other hand want some plugins that we own directly,
reloadable. And the fact that static variables didn't work anymore took us by
surprise mainly because we weren't aware of it (totally our fault). Now that we
understand that it is somewhat of an expected/intended behavior, we'd make
necessary adjustments (e,g updating the plugin) if we want to use the reload
feature.
So, it's not necessarily about whether the user is qualified to make a
decision, rather a matter of organizational structure and policy for how ATS is
operated. We could clearly document the behavior and provide recommendations to
the users.
Does it make sense?
Thanks!
Sudheer
On Thursday, May 7, 2020, 07:12:40 PM PDT, Alan Carroll
<[email protected]> wrote:
Leif;
If the plugin can be global or remap but not both, I don't see why (2) limits
anything. The entire issue is irrelevant for such plugins, because the
situation of reloading the remap DSO but not the global cannot occur, In fact,
option (3) or (4) would enable detecting this and issuing a warning.
Approach (1) was my first thought, but I think the problem there is whether the
plugin can work as a global and a reloadable remap is a property of the plugin
implementation, not any particular remap rule. That is, for a specific plugin,
there's really no choice about whether to use "@plugin" or "@global" - the
configuration must get it right or the plugin crashes. Every time. Every rule.
It is for this reason I disagree with Leif's view the user should decide. The
user's opinion is irrelevant - the plugin works in this mode, or it doesn't.
And as our friends at LinkedIn discovered, some rather basic C++ decisions
(such as using static variables) will prevent a plugin from working in this
mode. On the other hand, if the plugin uses the "User Args" feature then it can
work, in which case what's the point of disabling the DSO reload? Unless the
plugin implementor is concerned about code skew between the global and remap
versions, which again the user is not qualified to decide.
My personal preference is (3), but I suspect after mysterious crashes with
plugins, we will have been happier with (4).
On Thu, May 7, 2020 at 7:42 PM Sudheer Vinukonda <[email protected]>
wrote:
+1 on the general idea to make the reloadability customizable per plugin.
However, I think it'd be more simple, cleaner and intuitive to not tie it to
whether or not a plugin is used both as a global and remap plugin.
In other words, approach (1) below but, instead of calling it "@global", we
could add a param which says "@reloadable=false" (the default value for
"@reloadable" can be "true").
The same param can then be used, when we eventually add relodability to global
plugins as well.
Thoughts?
On Thursday, May 7, 2020, 05:24:09 PM PDT, Alan Carroll
<[email protected]> wrote:
As part of the ATS 9 upgrade, a feature was added so that remap plugins could
have their DSO reloaded. This means not just the configuration, but the
implementation itself. While very useful, this has some unfortunate side
effects with plugins that are used in both a global and remap context. To
alleviate this, a configuration variable as added to disable the feature.
Although reasonable, this is a rather heavy handed way to deal with the
problem. What would be better is the ability to reload the DSO or not on a per
remap plugin basis. I have a few ways this could be done:
1) Add the keyword "@global" to "remap.config". This would behave exactly as
"@plugin" except it would prohibit reloading of the DSO for that plugin.
2) Have the remap reload configuration check to see if the plugin is also a
global plugin and disable remap DSO reload for that plugin.
3) Add a flag to the global plugin registry information which can be set during
TSPluginInit which disables DSO reloading for that plugin, should it occur in
"remap.config". This is similar to (2) but requires a plugin to prohibit DSO
reloading. The call woud be TSPluginDSOReloadEnable(flag) and would only be
valid when called from TSPluginInit.
4) As (3), except the flag is set by default and must be cleared to enable DSO
reloading in "remap.config".
I'm willing to see if I can make this work, but I would like to have some
feedback on the preferred approach first.
