This PR will add a possibility to add labels to a node in ringpop. Labels set on a node will be gossiped around the network in the same fashion as updates to the status of a node do and therefore will converge so all members of the membership will have the same labels for all nodes during normal operation where the membership is converged.

Labels can be used to annotate nodes with extra information. In the examples an application is provided where a role for a node is set on its labels. Other members of the membership can then query ringpop for all nodes that fulfill a specific role.

• [x] Add test to make sure setting private labels from public interface returns error (from: #172)
• [x] Revisit locking to prevent races

• Works on a local OSX machine with a fresh $GOPATH.
• Works on travis-ci.
• Does not work on a fresh Docker golang:1.6 instance due to possibly different thrift version (not verified). However, the dev branch doesn't work too, so it's a separate problem.

To make sure that applications can't interfere with ringpop internals on labels we reserve all labels prefixed with __ (double lodash) for ringpop. Applications will receive an error when they try to set a label that starts with this prefix.

This patch just adds very basic proxy functionality (I am actually in the process of writing some integration test which Jeff pointed so that I can actually validate the handling of the proxy request, etc.) I am just putting it out there for others to see.

TODO:

• Add more tests to properly test this functionality
• Fixup the proxy request handling after getting an actual proxy going
• Increase code coverage (go test --cover gives only 74.2% now)

Since labels are gossiped around for all members it can cause gossip bloat when used irresponsibly. This will add enforceable limits on labels to prevent the such bloat from happening. Labels will be ignored when the application tries to set a label or multiple labels that would violate the allowed budget for the labels.

With this refactor we keep an explicit copy of what the local state of a member is and reincarnate from there if we receive a gossip that would overwrite the state of our node in the network.

It is analogous to https://github.com/uber/ringpop-node/pull/291

Using cram to execute and verify instructions in the following files:

• examples/ping-json/README.md
• examples/ping-thrift-gen/README.md
• examples/ping-thrift/README.md

Currently, all of the tests are failing due to incomplete instructions in the README, but opening the pull request anyway to set the path forward to fixing them.

Previously the lookup stat was emitted from the event-handler inside of ringpop.go when a LookupEvent was emitted. However, the lookup-event is emitted on ringpop itself so it's internal event-handler isn't triggered.

In preparation for automated perf. tests we want to be able to emit stats to a file/network from testpop.

This PR adds a new flag to testpop to control where the stats should go; if the flag is omitted, no stats are emitted.

Two things going on:

• maxP should never be lower than 15, considering the math used to adjust it.
• after bootstrap, the initial value for maxP doesn't reflect the ring size.

Restructure ping-reqs and put them into a indirectPing -> (reached bool, errs []errors) function The test is said to be inconclusive if all nodes that should ping the target are unreachable.

Add tests for all seven possible ping-req scenarios.

Add a ListenerFunc type to the swim/events.go that turns a function into a object that implements EventListener.

Hi, I am trying to use ringpop with http.Server. The server's handler receives requests and uses ringpop to handle or forward the requests to other servers on the ring. But I am unable to find any docs or guides or examples. Can someone please share a link to relevant examples? Thanks.

Every exported function in a program should have a doc comment. The first sentence should be a summary that starts with the name being declared. From effective go.

I generated this with CodeLingo and I'm keen to get some feedback, but this is automated so feel free to close it and just say "opt out" to opt out of future CodeLingo outreach PRs.

Could we please get some more info about what this means? Should people avoid looking at ringpop as it's a discontinued project that uber is moving on from, or is it because you consider it feature complete and in maintenance mode?

service Foo {
   string ping()
}

service Bar extends Foo {
}

The generated code fails with this error:

cannot use adapter (type *RingpopBarAdapter) as type TChanBar in return argument:
	*RingpopBarAdapter does not implement TChanBar (missing Ping method)

Examples of how tchannel-go thrift gen template handles it https://github.com/uber/tchannel-go/blob/dev/thrift/thrift-gen/tchannel-template.go#L55 https://github.com/uber/tchannel-go/blob/dev/thrift/thrift-gen/tchannel-template.go#L45

This fixes two leaking goroutines from the ringpop timers. There is still one more leaking goroutine that I'm aware of in rcrowley/go-metrics:

https://github.com/rcrowley/go-metrics/blob/master/meter.go#L218-L225

That's a ticker that would also require a stop channel.