medusar commented on issue #2306:
URL: https://github.com/apache/rocketmq/issues/2306#issuecomment-699804034
> > Yes, the default `SelectorProvider` will choose the right `Selector`
based on the system, as for Linux, it will use `EPollSelectorProvider` if the
kernel is 2.6 or newer otherwise it will choose `PollSelectorProvider`.
> > But as the the JDK api says, users can specify their own
SelectorProvider:
> > ```
> > The first invocation of this method locates the default provider object
as follows:
> >
> > If the system property java.nio.channels.spi.SelectorProvider is defined
then it is taken to be the fully-qualified name of a concrete provider class.
The class is loaded and instantiated; if this process fails then an unspecified
error is thrown.
> >
> > If a provider class has been installed in a jar file that is visible to
the system class loader, and that jar file contains a provider-configuration
file named java.nio.channels.spi.SelectorProvider in the resource directory
META-INF/services, then the first class name specified in that file is taken.
The class is loaded and instantiated; if this process fails then an unspecified
error is thrown.
> >
> > Finally, if no provider has been specified by any of the above means
then the system-default provider class is instantiated and the result is
returned.
> >
> > Subsequent invocations of this method return the provider that was
returned by the first invocation.
> > ```
> >
> >
> > So, IMHO, if it is the purpose of RocketMQ to disable user-specified
Selector and use `EPollSelectorProvider` regardless of user configuration, use
only `Selector.open()` would not work.
>
> I agree with some of your views，but i think that,if the code Clearly
indicate the use like `if (isLinuxPlatform()) { try { final Class<?>
providerClazz = Class.forName("sun.nio.ch.EPollSelectorProvider");`
>
> i think the use like this,The user has no choice,The effect is that the
user uses EPollSelectorProvider on the linux platform,so much code can use
Selector.open() instead, and why user must use EPollSelectorProvider in linux
as the only choose ? may be they can use custom selector,so i think we need
clear some unnecessory code
I agree with you, `Selector.open()` is much simpler and clean.
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