Ranch 2.0 adds support for multiple connection supervisors.
Ranch 1.x had a bottleneck because it used only a single connection supervisor. This was more evident when many connections were dropped at once as the supervisor couldn't keep up and failed to accept new connections while cleaning up the old ones. Ranch 2.0 behaves much better in this scenario by default. Multiple connection supervisors also helps with concurrently accepting new connections.
Ranch 2.0 also adds experimental support for opening more than one listening socket on a single port.
Ranch 2.0 is compatible with Erlang/OTP 21.0 onward. Support for Erlang/OTP 19 and 20 has been removed.
ranch.appup file necessary for performing release upgrades. A test suite has been added to confirm release upgrades work from one tag to the next. Numerous fixes were made that will also improve error recovery. Release upgrades will only be supported from Ranch 2.0 onward.
num_conns_sups option has been added. It allows configuring the number of connection supervisors. It now defaults to
num_accceptors. The old behavior can be obtained by setting this value to 1.
logger option is no longer experimental. It now defaults to
logger instead of
ranch_server goes down. It is no longer necessary to embed
ranch_sup and the recommendation is now to just start Ranch normally when using embedded listeners.
num_listen_sockets option has been added. It allows opening more than one listening socket per listener. It can only be used alongside the Linux
SO_REUSEPORT socket option or equivalent. It allows working around a bottleneck in the kernel and maximizes resource usage, leading to increased rates for accepting new connections.
socket option was removed. A more viable solution is to define a custom transport module that returns a fresh socket when
Transport:listen/1 is called.
Transport:listen/1 and its implementations in
ranch_ssl have changed to accept a map of transport options instead of only socket options.
Transport:messages/0 return value now includes the tag used for passive messages.
Socket argument was removed from
Protocol:start_link/3. The socket must now be obtained by calling
ranch:handshake_cancel/1 can be used to perform a two steps handshake. These functions may not be supported by all transports.
NumAcceptors argument was removed from
ranch:child_spec/5 and moved to the transport options.
ranch:opts() map or only socket options as-is. Individual transport options are now validated as well. The
ranch:opts() map must be used when socket options also use a map. This applies to the
ranch:info/1,2 now returns a map containing each listener's information rather than a list of key/values. The key
num_acceptors was removed as it can be found in the transport options.
ranch:set_transport_options/2 no longer requires the listener to be suspended. Which options apply immediately, on suspend/resume or on restart has been documented. Some work has also been done to make these option changes more predictable.
ranch:accept_ack/1 has been removed in favor of
ranch:remove_connection/1 will now resume a sleeping acceptor process when applicable.
ranch:remove_connection/1 from a connection process would crash the respective connection supervisor. This has now been fixed.
stampede, a chaos monkey style testing tool. Currently includes three scenarios: normal TCP and TLS listeners and embedded TCP listener. This new test suite helped uncover a misplaced
monitor/2 call added during the development of Ranch 2.0 (we were using a similar tool,
havoc, at the time of finding that issue).
1 + ceil(math:log2(NumChildren)) to allow room for errors when they have many children.
ssl:handshake/1,2,3 instead of
ranch_ssl:ssl_opt() type has been updated to conform with Erlang/OTP 23.0.
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