Api versioning

At first I recommend you to get more familiar with NATS because it's just a simple pub/sub system. In hemera every service is located by his topic name and the topic in NATS is the subject of the subscriber. If you want to version your service you can represent it in the topic name.

On service level

hemera.add({
  topic: 'math:v1.0'
})

or with wildcards. For more informations see Nats protocol.

hemera.add({
  topic: 'math:v1.*'
})

On application level

You can version your service by a different pattern so that your service is always accessible with the same topic. In this way you have the most flexbility because both services can co-exist.

hemera.add({
  topic: 'math',
  cmd: ' add',
  version: '1'
})

or with regex:

hemera.add({
  topic: 'math',
  cmd: ' add',
  version: /1\.[0-9]/
})

On server level

Imagine a region eu-west should only have access to a specific api version. You can connect the clients with a different NATS server which exposed a restricted set of services. After a certain period of time you can combine both server to a cluster. This use case is very special but possible. You have three options.