Motiviation:
Linux provides the TCP_NOTSENT_LOWAT socket option. This can be used to control how much unsent data is queued in the tcp kernel buffers. This can be important when application level protocols (SPDY, HTTP/2) have their own priority mechanism and don't want data queued in the kernel.
Modifications:
- The epoll module will have an additional socket option TCP_NOTSENT_LOWAT
- There will be JNI methods to control the underlying linux socket option mechanism
Result:
Linux EPOLL module exposes the TCP_NOTSENT_LOWAT socket option.
Motivation:
As we plan to have other native transports soon (like a kqueue transport) we should move unix classes/interfaces out of the epoll package so we
introduce other implementations without breaking stuff before the next stable release.
Modifications:
Create a new io.netty.channel.unix package and move stuff over there.
Result:
Possible to introduce other native impls beside epoll.
Motivation:
Using Unix Domain Sockets can be very useful when communication should take place on the same host and has less overhead then using loopback. We should support this with the native epoll transport.
Modifications:
- Add support for Unix Domain Sockets.
- Adjust testsuite to be able to reuse tests.
Result:
Unix Domain Sockets are now support when using native epoll transport.
Motivation:
So far, we relied on the domain name resolution mechanism provided by
JDK. It served its purpose very well, but had the following
shortcomings:
- Domain name resolution is performed in a blocking manner.
This becomes a problem when a user has to connect to thousands of
different hosts. e.g. web crawlers
- It is impossible to employ an alternative cache/retry policy.
e.g. lower/upper bound in TTL, round-robin
- It is impossible to employ an alternative name resolution mechanism.
e.g. Zookeeper-based name resolver
Modification:
- Add the resolver API in the new module: netty-resolver
- Implement the DNS-based resolver: netty-resolver-dns
.. which uses netty-codec-dns
- Make ChannelFactory reusable because it's now used by
io.netty.bootstrap, io.netty.resolver.dns, and potentially by other
modules in the future
- Move ChannelFactory from io.netty.bootstrap to io.netty.channel
- Deprecate the old ChannelFactory
- Add ReflectiveChannelFactory
Result:
It is trivial to resolve a large number of domain names asynchronously.
Motivation:
There is currently no epoll based DatagramChannel. We should add one to make the set of provided channels complete and also to be able to offer better performance compared to the NioDatagramChannel once SO_REUSEPORT is implemented.
Modifications:
Add implementation of DatagramChannel which uses epoll. This implementation does currently not support multicast yet which will me implemented later on. As most users will not use multicast anyway I think it is fair to just add the EpollDatagramChannel without the support for now. We shipped NioDatagramChannel without support earlier too ...
Result:
Be able to use EpollDatagramChannel for max. performance on linux
Motivation:
In linux kernel 3.9 a new featured named SO_REUSEPORT was introduced which allows to have multiple sockets bind to the same port and so handle the accept() of new connections with multiple threads. This can greatly improve the performance when you not to accept a lot of connections.
Modifications:
Implement SO_REUSEPORT via JNI
Result:
Be able to use the SO_REUSEPORT feature when using the EpollServerSocketChannel
Motivation:
The epoll testsuite tests the epoll transport only against itself (i.e. epoll x epoll only). We should test the epoll transport also against the well-tested NIO transport, too.
Modifications:
- Make SocketTestPermutation extensible and reusable so that the epoll testsuite can take advantage of it.
- Rename EpollTestUtils to EpollSocketTestPermutation and make it extend SocketTestPermutation.
- Overall clean-up of SocketTestPermutation
- Use Arrays.asList() for simplicity
- Add combo() method to remove code duplication
Result:
The epoll transport is now also tested against the NIO transport. SocketTestPermutation got cleaner.
