Contribute Custom Erlang Network Protocol to CouchDB

[jiahuili430]

Overview

Enable Custom Erlang Network Protocol for CouchDB Classic.

• Add the couch_dist.erl app with tests.
• Update the vm.args config lines with documentation.
• Updateremsh.tls script, configure for development, and release script remsh

Testing recommendations

make eunit apps=couch_dist suites=couch_dist_tests

Related Issues or Pull Requests

Checklist

• Code is written and works correctly
• Changes are covered by tests
• Any new configurable parameters are documented in rel/overlay/etc/default.ini
• A PR for documentation changes has been made in https://github.com/apache/couchdb-documentation

[wohali]

@jiahuili430 Did you mean to close this? It seems promising!

[jiahuili430]

I will reopen this PR, and try to finish it next week.

[nickva]

Do we recall the reason we couldn't use the Erlang provided tls_dist as described here: http://www1.erlang.org/doc/apps/ssl/ssl_distribution.html and use a custom module?

Also currently it seems this module won't be used anywhere it's not referenced from any place in the code (even in comments)

[nickva]

It still seems we are just proxy-ing the callbacks directly to the Erlang/OTP provided inet_tls module? So our module is not doing anything differently than the legacy behavior as described in https://erlang.org/doc/apps/ssl/ssl_distribution.html. There is even a newer way of specifying just a single conf file, which seems nice -proto_dist inet_tls -ssl_dist_optfile "/path/to/tls.conf" but perhaps we can just refer to those docs in the vm.arg or docs files.

[jiahuili430]

@nickva

It still seems we are just proxy-ing the callbacks directly to the Erlang/OTP provided inet_tls module? So our module is not doing anything differently than the legacy behavior as described in https://erlang.org/doc/apps/ssl/ssl_distribution.html. There is even a newer way of specifying just a single conf file, which seems nice -proto_dist inet_tls -ssl_dist_optfile "/path/to/tls.conf" but perhaps we can just refer to those docs in the vm.arg or docs files.

I haven't finished yet, still working on it. Just add TCP.
Thanks for the review

[nickva]

@jiahuili430

I haven't finished yet, still working on it. Just add TCP.

ah, that makes sense

[jiahuili430]

Thanks to everyone who helped me complete this PR, especially @nickva, @iilyak, and @rnewson.

@nickva found the bug in listen/2, we cannot use node() to return node info. Because when setting up CouchDB, node() cannot return the name of the node because it is not connected to CouchDB yet.
@iilyak, he helped the software design part to make the application more scalable and extensible.
Thank you, @rnewson. Without your code, we cannot figure out how to enable custom erlang network protocol for CouchDB.

[nickva]

+1 Nice work!

[nickva]

We'd want documentation PR as well probably. It could probably re-iterate some of the comments in the vm.args file

[jiahuili430]

We'd want documentation PR as well probably. It could probably re-iterate some of the comments in the vm.args file

Add documentation: apache/couchdb-documentation#673

[nickva]

Well done, @jiahuili430. Merging to 3.x