Swallow fatal log when ignore is specified

[aeroastro]

The primary objective of this PR is to swallow fatal log in addition to exception, which has been supported since 6ae36e4.

In my humble opinion, when HTTP status code is explicitly specified with ignore option, receiving the status code is not fatal. For example, [404] fatal log invoked by checking document existence by HEAD request is not so informative nor required, I think.

After this PR is merged, hopefully, I also would like to replace Elasticsearch::API::Utils.__rescue_from_not_found with ignore option of perform_request, which is simpler and more efficient way with better maintainability.

[karmi]

Hi, thanks for the patch! It's indeed better to swallow the exception when the ignore parameter matches. I've noticed that the patch would cause "double logging" of the request/response, so I've fixed that in 8f6bb49.

Regarding replacing Elasticsearch::API::Utils.__rescue_from_not_found with ignore, here's the problem: I've deliberately designed the libraries as independent, so elasticsearch-transport handles only the connection stuff (HTTP, reloading connections, retries, etc) and elasticsearch-api handles only the Elasticsearch API related things (adding the Ruby methods for APIs, composing URLs, etc).

The reason is not academic -- I want the "API" to be independent on the client implementation in the elasticsearch-transport library, because people might want to use the Ruby API methods with a completely different client, possibly of their own. The only contract right now is the perform_request(method, path, params={}, body=nil) method, and adding the Elasticsearch-specific ignore options to the params feels to me to be cumbersome, weird, and brittle.

[aeroastro]

Sorry for the late response, and thank you so much for providing detailed review and making this patch available.

I understand the designed independence of elasticsearch-api from client implementation like elasticsearch-transport, and now I also think it is not a good idea to replace Elasticsearch::API::Utils.__rescue_from_not_found with ignore option.

After reading some codes in elasticsearch-api libraries in light of independence, I come up with another idea to improve independence. It would be very helpful if you could take a look at a PR I am going to send later.

[karmi]

@aeroastro, thanks for the understanding, please ping me on the new PR if I slip. I'm gonna be offline for the better part of the week, so I'll try to keep it in mind when I'll get to reviewing PRs next week.