TLDR: If you use a spec-compliant JSON parser, you will observe no change in Mesos 1.7.x and everything will continue to work as before.
Longer version: JSON allows strings to be encoded in several different ways. For example, "/" can be encoded directly as "/", or "\/", "\u002F", or "\u002f". A spec-compliant parser [1] must handle these and produce the same result for each. In Mesos 1.7.0, we're adopting rapidjson [2] in order to provide performance improvements to /state serving as well as all other json serving and serialization paths. Rapidjson will encode strings in a spec-compliant way, but the choices differ from the original JSON serialization code in Mesos (e.g. rapidjson encodes "/" unescaped whereas we previously encoded the escaped form "\/"). Please be sure that your JSON libraries used for parsing comply with one of the JSON specs. There are several updates to RFC 4627, but they are all equivalent from the perspective of string encoding and parser requirements for strings FWICT. There are some other topics that warrant discussion at some point, like number precision, but we're not changing anything in Mesos 1.7.0 related to this. Ben [1] https://tools.ietf.org/html/rfc8259#section-9 [2] http://rapidjson.org/