Unique Bus ID When Deployed To Kubernetes

[ryanjbaxter]

When we deploy an app to Kubernetes we should try to come up with an ID to use that is unique to the container

[spencergibb]

See

spring-cloud-bus/spring-cloud-bus/src/main/java/org/springframework/cloud/bus/BusEnvironmentPostProcessor.java

Lines 51 to 56 in 2440fad

	// TODO: move this to commons
	// @checkstyle:off
	private String getDefaultServiceId(ConfigurableEnvironment environment) {
	return "${vcap.application.name:${spring.application.name:application}}:${vcap.application.instance_index:${spring.application.index:${local.server.port:${server.port:0}}}}:${vcap.application.instance_id:${random.value}}";
	}
	// @checkstyle:on

I wonder if we take this opportunity to move that to commons

[ryanjbaxter]

Probably a good idea to move to commons

[ryanjbaxter]

@spencergibb I was looking into this a bit....

1. After googling a bit I didn't see an obvious way to get a container id when running in a pod

2. I took a step back and thought if we just had a better way of generating a unique id (as opposed to it including a random number) it wouldn't really matter if we could access something like a container id in a pod

So I was poking around commons and found this code which is quite similar to what we have in bus already

https://github.com/spring-cloud/spring-cloud-commons/blob/master/spring-cloud-commons/src/main/java/org/springframework/cloud/commons/util/IdUtils.java#L37-L56

It uses spring.application.instance_id which we dont use in bus, could this possible solve the problem? Would that id be the same after context refreshes? I suppose I could just test it out, but wondering if you know off the top of your head. I also just read in an old blog post that spring.application.instance_id would only be set when running in Cloud Foundry 😠

[spencergibb]

yeah, instance_id is gonna have the same problem.

My thought was a new random property source that, given a key, cached the random value.

cloudrandom.app.long would only ever generate 1 random long for the app key.

[ryanjbaxter]

This was implemented in spring-cloud/spring-cloud-commons#719