Of one starts Hibernate Search without the Elasticsearch cluster being reachable, we get something like this:
And then we get a bootstrap failure with a similar message.
The first log mentioning that we're "continuing bootstrap" is misleading, since most of the time we will not continue bootstrap, because there's only one backend and it failed to start. Not sure we can do much about this, but maybe we should have a look.
The second exception mentioning the request and response is confusing, because it mentions a null response. We should probably format the message differently, or even remove it completely, when we failed to send the request.
The actual message that will help users fix the problem is buried in the 2nd cause. It should be more visible.