webapi: listen on multiple interfaces/ports

[swillden]

The primary use case is to allow a node to be accessed via either HTTP or HTTPS. Other uses might be for a multihomed host to listen on different ports on each interface, or to listen on a subset of the available interfaces (but more than one), etc.

[warner]

As discussed in email, let's use a comma-separated list of strports specifications in web.port=, since I think commas are not normally a part of strports strings.

Shawn pointed out that it's not clear what to do with the BASEDIR/node.url file that is written out at node startup when there are multiple web ports. I'd suggest only writing out the URL for the first web.port specification, and documenting the config value to encourage folks to put the cheapest locally-reachable port (e.g. non-encrypted localhost HTTP) as the first value.

[swillden]

I've attached a very simple patch that implements multi-port listening. It still needs unit tests, but as I indicated on the mailing list I'm not sure where to implement those. If someone who knows the test infrastructure could give me some guidance, I'd be glad to write some tests.

[swillden]

Very simple multi-listener patch

[warner]

the patch looks good. testing it is a challenge.. the most obvious approach would be to start a client listening on two separate ports, then make sure that you can hit the welcome page over both of them. But we don't want to use statically-assigned port numbers, because that may collide with some other service running on the same host as the unit tests, or with another instance of the unit tests being run at the same time (out of a different source tree).

I guess what I'd suggest is to have the unit test use web.port=tcp:0,tcp:0. That will cause the client to start listening on two (separate) kernel-allocated ports. The first will get written into node.url, where the unit test can read it and verify that it can hit the welcome page. Then, use the following code to reach into the WebishServer and locate the listeners, so we can get both their port numbers, and check that the welcome page is reachable from both (for a total of three separate GETs):

 c = client
 ws = c.getServiceNamed("webish")
 for s in ws:
   # this iterates over all Service children of the WebishServer
   if isinstance(s, twisted.application.internet.TCPServer):
     yield s._port.getHost().port

I'd put the test in test_web.Grid, and take advantage of the client_config_hooks argument to set_up_grid to change the web.port= argument on the first client (see test/no_network.py around line 191).