[DISCUSS] Run plugins according to the configuration order instead of priority

[Ming Wen <we...@apache.org>]

hello, dev,

Now each plug-in of Apache APISIX has a priority attribute. If multiple
plug-ins are configured on an API, in a certain phase (rewrite/log and
other nginx phases), these will be executed in the order of priorities.

This design brings two problems:
1. Developers always need to set priority when adding new plug-ins,
otherwise it will conflict with existing plug-ins.
2. When multiple plug-ins are set, it is difficult to distinguish the order
in which these plug-ins are executed, which brings some troubles to
debugging. It is impossible for developers to remember the priority
attributes of all plugins.

So, can we not use the priority, but the configuration order of the
plug-ins (the earliest execution at the top of the plug-in list) to execute
sequentially?

In this way, developers will no longer have any doubts about the run order.

Of course, there is no perfect technical solution, it will also bring a
problem:
if the developer configures the wrong order, it will bring some risks. For
example, a developer want to run kafka plugin for send log first, then run
request rewrite plugin to change http header. This is impossible.

However, this risk is controllable, and we can add two judgments:
1. Make stage judgments in the Admin API, for example, it is not allowed to
execute plug-ins in the rewrite stage after the plug-ins in the log stage;
2. Make obvious interactive prompts and tests on the dashboard.

What do you think?

Thanks,
Ming Wen, Apache APISIX PMC Chair
Twitter: _WenMing

Re: [DISCUSS] Run plugins according to the configuration order instead of priority

[wei jin <kv...@apache.org>]

I think neither priority nor order can give users an intuitive
understanding of the execution order of plugins, because of the concept of
nginx phase.

For developers, we need to list a table in the document to publicize the
execution order after the combination of the priority of the plug-in and
the plug-in phase , so that it is convenient for developers and team review.

For users, we need to use some API feedback to inform users of the
execution order of plugins bound to a route, or how many routes a plugin is
bound to.

Chao Zhang <to...@apache.org> 于2021年2月27日周六 下午12:18写道：

> Currently the plugin is embedded as an object inside route, we may also
> support the array type. When the plugin is object, just use the priority
> way; when it’s an array, running them from top to bottom (it’s not
> absolutely right since the concept of phase).
>
> Also, mention the changes in FAQs and Docs, what’s more, the dashboard UI
> needs some friendly prompts to mention the order.
>
> Ming Wen <we...@apache.org>于2021年2月27日 周六11:50写道：
>
> > hello, dev,
> >
> > Now each plug-in of Apache APISIX has a priority attribute. If multiple
> > plug-ins are configured on an API, in a certain phase (rewrite/log and
> > other nginx phases), these will be executed in the order of priorities.
> >
> > This design brings two problems:
> > 1. Developers always need to set priority when adding new plug-ins,
> > otherwise it will conflict with existing plug-ins.
> > 2. When multiple plug-ins are set, it is difficult to distinguish the
> order
> > in which these plug-ins are executed, which brings some troubles to
> > debugging. It is impossible for developers to remember the priority
> > attributes of all plugins.
> >
> > So, can we not use the priority, but the configuration order of the
> > plug-ins (the earliest execution at the top of the plug-in list) to
> execute
> > sequentially?
> >
> > In this way, developers will no longer have any doubts about the run
> order.
> >
> > Of course, there is no perfect technical solution, it will also bring a
> > problem:
> > if the developer configures the wrong order, it will bring some risks.
> For
> > example, a developer want to run kafka plugin for send log first, then
> run
> > request rewrite plugin to change http header. This is impossible.
> >
> > However, this risk is controllable, and we can add two judgments:
> > 1. Make stage judgments in the Admin API, for example, it is not allowed
> to
> > execute plug-ins in the rewrite stage after the plug-ins in the log
> stage;
> > 2. Make obvious interactive prompts and tests on the dashboard.
> >
> > What do you think?
> >
> > Thanks,
> > Ming Wen, Apache APISIX PMC Chair
> > Twitter: _WenMing
> >
>

Re: [DISCUSS] Run plugins according to the configuration order instead of priority

[Chao Zhang <to...@apache.org>]

Currently the plugin is embedded as an object inside route, we may also
support the array type. When the plugin is object, just use the priority
way; when it’s an array, running them from top to bottom (it’s not
absolutely right since the concept of phase).

Also, mention the changes in FAQs and Docs, what’s more, the dashboard UI
needs some friendly prompts to mention the order.

Ming Wen <we...@apache.org>于2021年2月27日 周六11:50写道：

> hello, dev,
>
> Now each plug-in of Apache APISIX has a priority attribute. If multiple
> plug-ins are configured on an API, in a certain phase (rewrite/log and
> other nginx phases), these will be executed in the order of priorities.
>
> This design brings two problems:
> 1. Developers always need to set priority when adding new plug-ins,
> otherwise it will conflict with existing plug-ins.
> 2. When multiple plug-ins are set, it is difficult to distinguish the order
> in which these plug-ins are executed, which brings some troubles to
> debugging. It is impossible for developers to remember the priority
> attributes of all plugins.
>
> So, can we not use the priority, but the configuration order of the
> plug-ins (the earliest execution at the top of the plug-in list) to execute
> sequentially?
>
> In this way, developers will no longer have any doubts about the run order.
>
> Of course, there is no perfect technical solution, it will also bring a
> problem:
> if the developer configures the wrong order, it will bring some risks. For
> example, a developer want to run kafka plugin for send log first, then run
> request rewrite plugin to change http header. This is impossible.
>
> However, this risk is controllable, and we can add two judgments:
> 1. Make stage judgments in the Admin API, for example, it is not allowed to
> execute plug-ins in the rewrite stage after the plug-ins in the log stage;
> 2. Make obvious interactive prompts and tests on the dashboard.
>
> What do you think?
>
> Thanks,
> Ming Wen, Apache APISIX PMC Chair
> Twitter: _WenMing
>