Question: Support for Consul v0.7.3 Node tags

[gamefundas]

Is there a plan to support Node tags which was recently added to Consul 0.7.3?

The real requirement for me is to be able able to route my calls to individual nodes in my service cluster. For example if Service-A has Node 1, 2, 3 then I would like to access them directly (non-loadbalanced way) via

http://fabio.host:port/service-A/node1
http://fabio.host:port/service-A/node2
http://fabio.host:port/service-A/node3

Even if the node names are numerical sequence it should be fine. We just need the ability to access the nodes via the fabio proxy.

I tried implementing this using consul-template + Nginx but came across fabio which seems to be doing most of the work for me in a simple plug and play manner. Would love to know if this feature can be implemented in some way.

[magiconair]

I'm wondering whether this is related to #101 (sticky load balancing).

[gamefundas]

I don't think this is related to #101 or sticky sessions. Perhaps my explanation is misleading.

In my scenario, fabio is able to create a load balanced route http://fabio.host:port/service-A
and accessing that lands me in one of the nodes. But what I need is the ability to hit Node-1, Node-2 and Node-3 independently.

[magiconair]

I already have variable expansion for the ${DC} variable which contains the consul data center. It is a trivial fix to also include the node meta data and lets say the node name and the address for example. However, since your services only have handlers for /service-A you would need to add the node name to the front and then use path stripping to get rid of it again, e.g. urlprefix-/${node}/foo strip=/${node} (note that this doesn't work yet since there is no expansion on the options) However, I don't know how this would affect your URLs.

The strip operator is really a strip prefix operator right now. I'd need to extend the syntax to do suffix stripping or general omission, e.g. strip=/${node}^ for suffix and strip=*/${node}/* or something similar. Another option could be to just say how many elements of the URL should be stripped since we know we're dealing with URLs.

# strip 1 element from the front of the URI '/foo'
urlprefix-/foo/bar strip=1

# strip 1 element from the back of the URI '/bar'
urlprefix-/foo/bar strip=-1

I think this is very much sticky load balancing since in essence you want all your requests for a specific route to go to the same server except that the LB shouldn't make the initial routing decision. You want to pick the host yourself. If fabio would honor a cookie or a header you can set you could achieve the same thing.

I haven't settled on an approach yet since I'm trying to figure out how to square this. Can you explain your specific use case?

[gamefundas]

Mine is not really a load balancing use case. Its merely routing calls to specific nodes. We have maintenance service endpoints on each nodes that requires us to reach the specific faulty node to either restart or perform basic support operations like purge cache etc. A load balancer would randomly route the call. We would like to target the faulty nodes and be able to hit the specific host.

Instead of numerical sequence, host names will also work.

[magiconair]

Why don't you just announce a unique route for that host, e.g. urlprefix-/admin/$HOSTNAME?

[gamefundas]

This might work. Didn't think that I could very much control how to create my route path.
Thanks.

Closing this one.

[magiconair]

You would need to have a handler for that on the upstream server though