Exception handling on "API down for maintenance"

リンクされた Promregator issue、CAPI release notes、full-error.txt から始め、JSON ではないメンテナンス応答と、それによって発生する CorruptedFrameException を理解してください。issue ではリポジトリのファイルやテストが指定されていません。作業は、プロジェクトがこの失敗をどこで扱うべきかを決定し、想定される例外処理を定義して初めて完了します。

Documented in the case of https://github.com/promregator/promregator/issues/96#issuecomment-490585118, Promregator (a consumer of cf-java-client) encountered the situation that the CF Cloud Controller did not respond with a proper response, but only returned the ASCII string

API down for maintenance

instead of the corresponding JSON.
I stumbled over https://github.com/cloudfoundry/capi-release/releases/tag/1.77.0, where the second line in the highlights suggests that this is a standard behavior of the platform (and also might have reported that error without providing the appropriate HTTP status code of 503).

Based on the logs, it seems that cf-java-client today reacts to just forward an exception of type io.netty.handler.codec.CorruptedFrameException. It is clear that the corresponding request cannot be fulfilled and some sort of error reporting/exception handling must take place in this case.

What is unclear to me is who should be in charge of handling such a kind of exception. I doubt that a consumer application should catch exceptions raised by netty due to a decoding issue. Moreover, the situation appears to be (perhaps not a desired situation, but still) a response that may happen from time to time. One may also argue whether this is covered by the contract.

What is your opinion about all this? Should the consumer of cf-java-client handle this kind of failure by catching io.netty.handler.codec.CorruptedFrameException?