Deployment groups work in conjunction with Service Discovery to support red/black style deployments. With red/black deployments you deploy a new version of a service while the old version of the service is still running. However, the old version is removed from Service Discovery. This way, the new version can be validated while the old version is in hot standby in case the new version fails and needs to reverted for some reason. You could even have three or more active versions with some in Discovery and some not. This can also be used to do A/B style testing.
Every instance is defined to be in one or more deployment groups via Soabase Configuration. There is always a "default" deployment group that instances are part of if not defined to be in other groups. Deployment Groups are service specific. i.e. the deployment group "v1.0" in service "cache" is different than a group with the same name in service "logging".
By default, deployment groups are active. They can be deactivated via the Admin Console or via Admin APIs.
Deployment groups are managed internally by an instance of DeploymentGroupManager. The default implementation stores deployment group active state in Dynamic Attributes. The key used is formed using this pattern (where SERVICE is the service name and GROUP is the group name):
_soabase_deployment_group_SERVICE_GROUP
The value of the attribute is "true" if the group is active or "false" if inactive. Instances that are part of an inactive deployment group will not be returned from Service Discovery.
If needed, you can use a custom DeploymentGroupManager.
To use something other than the default DeploymentGroupManager implementation, follow these steps:
DeploymentGroupFactory
Your DeploymentGroupFactory implementation is like other Dropwizard factories. It should be both configuration and a factory. Use DefaultDeploymentGroupFactory.java as an example. This class must be annotated with JsonTypeName and given a unique name. You then use this name as the value for the attributes type in your configuration file.
DeploymentGroupManager
Your implementation does the actual work of Deployment Group management. The details will depend on your implementation's needs.
ServiceLoader files
Like other Dropwizard plugins, your implementation needs Service Loader files. In the io.dropwizard.jackson.Discoverable file add a line containing: io.soabase.core.features.discovery.deployment.DeploymentGroupFactory. In the io.soabase.core.features.discovery.deployment.DeploymentGroupFactory file add a line the with fully-qualified path name of your class. E.g. com.me.my.MyDeploymentGroupManager