Flux API: replace json_object with string

[garlick]

json_object appears in the Flux API, which creates a dependency on json-c for users.

Consider revising the API so that strings are passed instead of json_object. This may include revising RFC 3 so that FLUX_MSGFLAG_JSON is replaced with FLUX_MSGFLAG_STRING.

[garlick]

Issue #76 proposes replacing JSON with opaque data in the KVS.

[grondo]

To clarify (sorry if this is obvious) but you'd be replacing json_object with a valid JSON string (In which case FLUX_MSGFLAG_JSON actually still applies), or is the proposal to replace json_object with arbitrary, unformatted string?

[grondo]

Just throwing another idea out there, maybe this is what you had in mind anyway, but if there is already generic get/set_payload message methods, can we just drop the json specific calls from the public APIs (keeping them perhaps as internal convenience functions) and note the payload format in msgflags?

This may be a gross oversimplification of the problem because I haven't traversed the entire API in awhile...

[garlick]

@grondo: you're probably right on both counts.

[garlick]

I kept the get/set_payload message methods in in PR #189 as it seemed like it was appropriate to have the validation that payload has terminating NULL, etc., testing message flags, etc., down there in the low level code.

[garlick]

PR #215 gets rid of json_object from libflux-core.so.

Since #76 is tracking the removal of json_object from the KVS interface, and libkvs.so is a separate library from the core, I think we can close this one.