Refactor urlprefix tags

[magiconair]

Related open issues: #1, #42, #44, #56, #75, #80, #105, #110, #129, #164
Related closed issues: #35, #45, #53, #87, #90, #93, #107

fabio currently uses the urlprefix- tag prefix to identify routes. The format is limited to specifying a host/path prefix which makes it difficult to allow optional features for a given route. Issue #42 mentions an alternative syntax which provides more options but is still primarily focussed on prefixes.

consul issue 1107 mentions a revamp of the API to provide generic KV support for services but doesn't provide a timeline. However, one suggestion is something like RFC 1464 which is used to store arbitrary k/v data in DNS TXT records.

fabio could use this as follows which would provide a generic key/value config mechanism which can also be moved to something else later. Note that RFC 1464 uses the backtick for escaping the =, and the backtick itself.

This would allow a generic mechanism to add options to routes and protocols other than HTTP like TCP to be configured properly.

fabio key=value key=value key=value

e.g.
fabio uri=host/path
fabio uri=host/path proto=http,https
fabio uri=host/path log=true cors=true strip=/path
fabio addr=1.2.3.4:6789 proto=tcp

Several design questions come to mind:

• Should multiple prefixes be specified as a multiple uri attributes in a single tag or as multiple tags?

The challenge here would be a length restriction in the tags but we could allow both multiple tags and multiple uri attributes to work around this.

• Should the protocol be specified separately or as part of the URL?

As part of the URL has the benefit of being familiar but will require duplication if a path should be exposed via HTTP and HTTPS but not WS. Therefore, uri=host/path proto=http,https might be more compact.

Another approach would be to use JSON but the quoting makes this more difficult.

[far-blue]

Each service in Consul is a single ip/port combination so this is really a 1-2-many mapping problem. This one ip/port could be routed differently (in theory) for http, https, wss and tcp. Clearly not all combinations of these make sense but you get the idea.

So I suggest 1 tag per protocol with each tag starting with the protocol and then providing the protocol-specific details. For http this would be the hostname/path to be routed, for tcp I assume it would just be the listening port, then followed by generic details such as weighting and logging etc.

So you'd have something like:

fabio-http foo.com/wibble
fabio-wss foo.com/api strip=/path
fabio-tcp 6789 log=true

you could also support mixed protocols such as:
fabio-http-https foo.com/wibble

If tags can't contain spaces then still best to avoid commas because of how Registrator works. Maybe use something like:
fabio-http=foo.com/wibble;log=true

[far-blue]

you could use fabio-proxy to refer to http & https & wss all at once.

[magiconair]

Another approach is to leave the urlprefix-host/path unchanged and allow for urlprefix-host/path key=val key=val ... This would provide the same flexibility will full backwards compatibility.

[MilesBehind]

Fantastic work on the project @magiconair!
When do you think, this key=val key=val may be implemented? Since spring-cloud-consul supports only this configuration in an application.yml file:

spring:
  cloud:
    consul:
      discovery:
        tags: foo=bar, baz=foobar

it would be nice if these key=val key=val expressions would be supported.

[magiconair]

OK, here is what I am going to do:

Step 1

Add support for key=val options to the existing urlprefix- tags. This keeps them backwards compatible and won't break any existing setups. The first option after the tag prefix is the route target. This should also work for a TCP or UDP proxy although it reads a bit awkward.

urlprefix-host/path
urlprefix-host/path proto=https strip=/path
urlprefix-1.2.3.4:5555 proto=tcp

Step 2

Add support for multiple tag prefixes to allow migration from urlprefix- to something more generic like fabio and add support for a route= option as an alias for the route target so that the previous example reads as:

fabio route=host/path
fabio route=host/path proto=https strip=/path
fabio route=1.2.3.4:5555 proto=tcp

which is equivalent to

fabio host/path
fabio host/path proto=https strip=/path
fabio 1.2.3.4:5555 proto=tcp

which is equivalent to

urlprefix-host/path
urlprefix-host/path proto=https strip=/path
urlprefix-1.2.3.4:5555 proto=tcp

Maybe step 2 won't be needed but I'd like to add step 1 ASAP to support additional use cases without breaking existing setups.

[magiconair]

Merged new route parser to master

[magiconair]

The new route parser is in use. Closing.