Hibernate Search fallback when Elastic search not available

Is there a fallback mechanism in Hibernate Search in order to be able to perform a search even when Elastic search cluster is not available? I know that the indexes are stored in Elastic search but can Hibernate search in this case just ignore the indexes and perform a default search? Is there a way to set this up?

Solution

No. If Hibernate Search uses an Elasticsearch backend, it uses only that backend. If Elasticsearch is down, Hibernate Search is down.

If you want a "default search" (whatever that means), you will need to implement it in your own code, e.g.:

if ( elasticsearch available ) {
   // execute a query using Hibernate Search
}
else {
   // implement some "default" search, whatever that means
}

As to how you determine whether Elasticsearch is available, you could send a request to Elasticsearch using the underlying Rest client, or alternatively just run schema validation (which will necessarily fail if Elasticsearch is not available).

EDIT: Perhaps a better approach would be to try a normal search, catch exceptions and then fall back, e.g.:

try {

}
catch (SearchException e) {
   if ( e.getMessage().contains("connect") ) {
       // implement some "default" search, whatever that means
   }
   else {
      throw e;
   }
}