When CachingGadgetsMacroMetadataProvider#getByMacroNameAndId method is called, it always does http request to load the feed. This is the case even for completely unrelated macro types. This problem causes Confluence to do http request every time every macro is loaded.
This can lead to saturation of the HTTP connection pool and result in Confluence being intermittently inaccessible.
The right fix would be to do http requests only for gadget macros, not for arbitrary ones.
In the short term, the offending gadget feed may be temporarily removed from: Confluence Admin > External Gadgets in order to avoid further outages. If you are unsure of the problematic feed, remove all of them. This will not remove the gadgets from the pages, it will just show an error in their place until you resolve the issue and add the gadget feed back in.
The long term fix is to upgrade to a fixed version.