Unix Sockets for HTTP Replication

[realtyem]

I need some help with the Typing, then this should be pretty much good to use.

• Fixes Support UNIX sockets for HTTP interfaces #4975

Unix socket support for federation and client Listeners has existed now for a little while(since 1.81.0), but there was one last hold out before it could be complete: HTTP Replication communication. This should finish it up. The Listeners would have always worked, but would have had no way to be talked to/at.

Instructions are the same as on the original Pull Request, but instead of setting client or federation, use replication instead. Otherwise, to make sure they match up properly, on the instance_map for any given worker that you wish to use with a Unix socket, swap out host and port with path(it's like there's a pattern or something).

As an example of before and after:

Before

homeserver.yaml/shared.yaml

listeners:
  - port: 8008
    bind_addresses: ['0.0.0.0']
    type: http
    tls: false
    x_forwarded: true
    resources:
      names: [client, federation]
  - port: 9093
    type: http
    resource:
      names: [replication]

instance_map:
  main:
    host: 127.0.0.1
    port: 9093
  worker1:
    host: 127.0.0.1
    port: 18010

worker1.yaml

worker_listeners:
  - port: 13000
    bind_address: 0.0.0.0
    type: http
    tls: false
    x_forwarded: true
    resources:
      - names: [client, federation]
  - port: 18010
    type: http
    tls: false
    x_forwarded: false
    resources:
      - names: [replication]

After

homeserver.yaml/shared.yaml

listeners:
  - path: /var/run/mainpublic.socket
    type: http
    resources:
      names: [client, federation]
  - path: /var/run/mainprivate.socket
    type: http
    resource:
      names: [replication]

instance_map:
  main:
    path: /var/run/mainprivate.socket
  worker1:
    path: /var/run/worker1-private.socket

worker1.yaml

worker_listeners:
  - path: /var/run/worker1-public.socket
    type: http
    resources:
      - names: [client, federation]
  - path: /var/run/worker1-private.socket
    type: http
    resources:
      - names: [replication]

P.S. Coming soon:

• Docs,
• Complement command line experiment hook up,
• [ ] and (maybe)fall over connections this might be separate, I need an Opinion.

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file.
• Pull request includes a sign off
• Code style is correct
  (run the linters)

Signed-off-by: Jason Little realtyem@gmail.com

[MadLittleMods]

TODO

[MadLittleMods]

If this is reverted back to Type[Model], the following lints are thrown:

synapse/config/workers.py:284: error: Argument 2 to "parse_and_validate_mapping" has incompatible type "<typing special form>"; expected "Union[Type[InstanceTCPLocationConfig], Type[InstanceUNIXLocationConfig]]"  [arg-type]

[realtyem]

Which is why I need help with the Typing. I was hoping @DMRobertson would be kind enough to lend a hand with that, as he had before.

[MadLittleMods]

@realtyem It seems like a couple of us have at least had a cursory try at addressing this with no success. Probably best to add # type: ignore[arg-type] with our best explanation on what might be going on. And if we're lucky cross-referencing a relevant mypy bug: https://github.com/python/mypy/issues

[realtyem]

For full disclosure(and to help with how extensive my confusion is), here is the full set of mypy readouts if you remove all the # type: ignore around this.

synapse/config/_util.py:89: error: Variable "model_type" is not valid as a type  [valid-type]
synapse/config/_util.py:89: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
synapse/config/workers.py:284: error: Argument 2 to "parse_and_validate_mapping" has incompatible type "<typing special form>"; expected "Union[Type[InstanceTcpLocationConfig], Type[InstanceUnixLocationConfig]]"  [arg-type]

I was hoping this would be a more useful generic function that could process other 'maps' as they are migrated to Pydantic. The website mentioned in the error message was where I got the TypeAlias from. I'm not sure it's a bug, really.

[MadLittleMods]

Thanks for the contribution @realtyem, being patient while I onboard to everything here, and being so attentive to make this as smooth as possible! 🐯