Unable to start index from backup if the state was not restored before

[sarthakn7]

This results in an error like this:

Apr 06, 2021 3:33:40 PM com.yelp.nrtsearch.server.grpc.LuceneServer$LuceneServerImpl startIndex
WARNING: error while trying to start index test_idx
java.lang.IllegalArgumentException: index test_idx was not saved or commited
	at com.yelp.nrtsearch.server.luceneserver.GlobalState.getIndex(GlobalState.java:240)
	at com.yelp.nrtsearch.server.grpc.LuceneServer$LuceneServerImpl.startIndex(LuceneServer.java:512)
	at com.yelp.nrtsearch.server.grpc.LuceneServerGrpc$MethodHandlers.invoke(LuceneServerGrpc.java:2781)
	at io.grpc.stub.ServerCalls$UnaryServerCallHandler$UnaryServerCallListener.onHalfClose(ServerCalls.java:172)
	at io.grpc.PartialForwardingServerCallListener.onHalfClose(PartialForwardingServerCallListener.java:35)
	at io.grpc.ForwardingServerCallListener.onHalfClose(ForwardingServerCallListener.java:23)
	at io.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.halfClosed(ServerCallImpl.java:331)
	at io.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$1HalfClosed.runInContext(ServerImpl.java:820)
	at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)
	at io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:123)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
	at java.base/java.lang.Thread.run(Thread.java:832)

The current workaround is to add the index in the state and restart nrtsearch so that the index name is present in the loaded state:

$ echo '{"test_idx":"test_idx"}' > primary_state/indices.0