Different plugins depend on the same plugin, Will the common plugin Init repeatedly? and how to avoid that?

[shuaizhilin]

Here is a question：

- Different plugins depend on the same plugin, Will the common plugin Init repeatedly？

I try it with a new test case like this:

func TestMultiPluginsDepsSamePlugin(t *testing.T) {
	RegisterTestingT(t)
	CommonPlugin := TestPlugin{
		PluginName:         "CommonPlugin",
	}
	plugin1 := PluginOneDep{
		PluginName:         "Plugin1",
		Plugin1: MissignCloseMethod{},
		Plugin2: CommonPlugin,
	}
	plugin2 := PluginTwoLevelDeps{
		PluginName:         "Plugin2",
		PluginTwoLevelDep1: plugin1,
		PluginTwoLevelDep2: CommonPlugin,
	}
	a := agent.NewAgent(agent.AllPlugins(&plugin1, &plugin2))
	Expect(a).ToNot(BeNil())
	Expect(a.Options()).ToNot(BeNil())
	Expect(a.Options().Plugins).ToNot(BeNil())
	logrus.DefaultLogger().Info(len(a.Options().Plugins))
	for _, plugin := range a.Options().Plugins {
		logrus.DefaultLogger().Info(plugin.String())
	}
}

The result show the agent.opts.Plugins has 10 plugins and has repeat CommonPlugin

Then I review the code of Start(), there isn't any code to avoid calling plugin.Init() repeatly. Is it necessary to avoid repeat
initialization?

[ondrej-fabry]

You should use pointers for the plugin instances. That way the plugin lookup will be able to recognize that it's same instance:

Also try using single parameter in AllPlugins. You can use dummy base plugin that will contain other top-level plugins as fields.

// ...
plugin1 := &PluginOneDep{ /* ... */ }
plugin2 := &PluginTwoDep{ /* ... */ }
base := struct {
	Plugin1 *PluginOneDep
	Plugin2 *PluginTwoDep
} {
    plugin1, plugin2,
}
a := agent.NewAgent(agent.AllPlugins(base))
// ...

I have to agree that this is not very clear behaviour and I will label this as a bug to be fixed. Thanks for reporting it @shuaizhilin