+++
date = "2019-07-18T07:00:00+01:00"
title = "Ranch 2.0 release candidate 1"

+++

Ranch `2.0.0-rc.1` has been released!

We are getting very close to releasing Ranch 2.0! As most of
the tremendous programming work was done by contributor Jan Uhlig,
I will yield the floor and let him describe what went into this
great release.

In Ranch 1.x, there is only one supervisor per Ranch listener
to start and manage connection processes. Under high load
(many clients rapidly connecting and/or disconnecting), the
message queue of this one supervisor could become congested,
leading to declining accept rates or a stalled listener.

Ranch 2.0 introduces the `num_conns_sups` option (defaulting
to the number of acceptors), which allows the message load to
be divided between the specified number of connection supervisors.
This improves accept concurrency at the same time.

Another bottleneck is a possible congestion of the syn queue of
a listening socket. The reason is located within the operating
system's TCP/IP implementation, and on Linux the `SO_REUSEPORT`
socket option was introduced to address it. What it boils down
to is that you can have more than just one socket listening on
the same port, causing the sockets to be load-balanced when
accepting connections.

Ranch 1.x always uses a single listening socket per listener,
shared between the acceptors. With a trick, starting multiple Ranch
listeners on the same port, it is already possible to make use
of the `SO_REUSEPORT` feature. But that's not ideal.

Ranch 2.0 introduces the `num_listen_sockets` option, which allows
to specify the number of listening sockets a Ranch listener should
employ, without having to use this trick. Whether you can use
`SO_REUSEPORT` at all and how to enable it depends on your
operating system, though.

Other changes include proper support for local (Unix Domain) sockets,
removing the restriction that a listener be suspended to change its
transport options and much needed improvements to embedded listeners.

In addition we have had patches merged to Erlang/OTP to add support
for active N to the `ssl` application (requires Erlang/OTP 21.3 or
above) and fix a number of smaller issues we encountered. We have
also helped detect and fix a bug in the Windows implementation of
active N that greatly reduced its performance in some cases.

To ensure that everything works correctly, new tests have been
written, and some existing tests were updated. A noteworthy addition
in this area is pitting Ranch against https://github.com/ankhers/havoc[Havoc],
a resilience testing tool that kills random processes and ports
in the system.

Cowboy users wishing to try Ranch 2.0.0-rc.1 will need to use Cowboy's
master branch at this time or wait for the upcoming Cowboy 2.7.0.
Cowboy has been made compatible with both Ranch 1 and 2.

Last but not least, aside from the changes mentioned above, we
are currently preparing a https://github.com/juhlig/prometheus_ranch[Prometheus collector]
for Ranch as well as an accompanying Grafana dashboard.

Ranch 2.0 requires Erlang/OTP 21 or above and is tested and supported
on Linux, FreeBSD, macOS and Windows.

A complete
list of changes can be found in the migration guide:
https://ninenines.eu/docs/en/ranch/2.0/guide/migrating_from_1.7/[Migrating from Ranch 1.7 to 2.0].

You can donate to this project via
https://github.com/sponsors/essen[GitHub Sponsors].
These funds are used to pay for additional servers for
testing. We will soon add two Raspberry Pi 4 in order
to have some ARM targets when testing.

As usual, feedback is appreciated, and issues or
questions should be sent via Github tickets. Thanks!
