TL;DR : How to switch elastic search hosts at runtime using spring-data-elasticsearch?
We have a spring boot application (v : 2.5.2) using spring data elasticsearch (v: 4.2.2).
I am using java configurations to initialize ES connection as mentioned in High Level Rest Client section of spring's documentation.
We have a requirement where we need to change the elasticsearch hosts at runtime and not manually restart our servers.
I tried restarting spring IOC on hostname config change using something similar to spring actuator's RestartEndpoint. But this seems to work only in spring's embedded tomcat and not with the external tomcat that we use.
Is there an alternate way to do this?
[This is required in case there is a disaster and we need to switch to backup]
Nothing out of the box.
One idea (I did not try it out): You'd need to create your own implementation of the ElasticsearchOperations interface, lets call it MyOperations and return that from the AbstractElasticsearchConfiguration#elasticsearchOperations() method which your configuration inherits. In this MyOperations implementation (which is a singleton Spring bean), you'd create a delegate ElasticsearchOperations with the same code like in the configuration class that is connected to normal cluster. Every method in your implementation then delegates to the corresponding method of the delegate.
In the failure case, your implementation would create a new delegate that now connects to the secondary cluster and replace the first one with it. Or create both and implement a toggle feature to switch between the two.