BlockingProcessStreamReader stalls when a subprocess is waiting on user input

[jainsahab]

After analysing googleapis/java-datastore#302 , we have a scenario where in some cases user can run commands which requires user input (manual intervention) and in those cases BlockingProcessStreamReader blocks on the following line waiting for the user input to happen, We do not flush the logs until an error happens, due to this user will never know what happened and there is no way they can pass the user input.

https://github.com/googleapis/google-cloud-java/blob/b72fe9d68c5892b587a5be36ba12b33165a71be9/java-core/google-cloud-core/src/main/java/com/google/cloud/testing/BlockingProcessStreamReader.java#L59

We probably have to put a timeout while starting a subprocess and dump all the startup logs incase the timeout happens, so that user gets the correct feedback.

[suztomo]

java-core is sdk-platform-java. Transferred the issue.

[blakeli0]

This is a very niche use case of local emulator testing, and the parent issue is not a priority at this moment. Closing as not planned for now, please re-open the issue if the parent issue becomes a priority again.