On Thu, 16 Jan 2020, 18:59 Zoltan Farkas, <zolyfar...@yahoo.com> wrote:
> answers inline > > On Jan 16, 2020, at 5:51 AM, roger peppe <rogpe...@gmail.com> wrote: > > On Wed, 15 Jan 2020 at 18:51, Zoltan Farkas <zolyfar...@yahoo.com> wrote: > >> What I mean with timestamp-micros, is that it is currently restricted to >> being bound to long, >> I see no reason why it should not be allowed to be bound to string as >> well. (the change should be simple to implement) >> > > Wouldn't have the implication of changing the binary representation too, > which is not necessarily desirable (it's bulkier, slower to decode and has > more potential error cases) ? > > > yes, it would, but this is how logical types work, and I see no good way > to change this. (this is what i meant by paying the readability cost in > place where it is irrelevant) > So you think that the JSON representation should always match the underlying type and ignore the logical type? I can understand the reasoning behind that, but it doesn't feel very user friendly in some cases (thinking of decimal and duration in particular). Given their privileged place in the specification, I was thinking that some logical types could gain privilege here. Aside: I'm a bit concerned about the potential for data corruption from interchange between timestamp-micros and timestamp-millis, which, as far as understand the spec, look like they'll be treated as compatible with each other. > > >> regarding the media type, something like: application/avro.2+json would >> be fine. >> > > Attaching the ".2" to "avro" rather than "json" seems to be implying a new > Avro version, rather than a new JSON-encoding version? Or is the idea that > the version number here is implying both the JSON-encoding version *and* the > underlying Avro version? The MIME standard seems to be silent on this > AFAICS. > > > the reason why I would use +json at the end is because it would be a > subtype sufix: https://en.wikipedia.org/wiki/Media_type#Suffix and most > browsers will recognize it as json, and potentially format it... > Ah, nice, I wasn't aware of RFC 6838. > > >> Other then that the proposal looks good. can you start a PR with the spec >> update? >> > > I can do, but I don't hold out much hope of it getting merged. I started a > PR with a much more minor change <https://github.com/apache/avro/pull/738> > almost 2 months ago and haven't seen any response yet. > > > Send out a email on the dev mailing list, the committers seem more > responsive lately... > I'll give it a go :) cheers, rog. > > > cheers, > rog. > >> >> —Z >> >> On Jan 15, 2020, at 12:30 PM, roger peppe <rogpe...@gmail.com> wrote: >> >> On Wed, 15 Jan 2020 at 16:27, Zoltan Farkas <zolyfar...@yahoo.com> wrote: >> >>> See comments in-line below: >>> >>> On Jan 15, 2020, at 3:42 AM, roger peppe <rogpe...@gmail.com> wrote: >>> >>> Oops, I left arrays out! Two other thoughts: >>> >>> >>> - I wonder if it might be worth hedging bets about logical types. It >>> would be nice if (for example) a `timestamp-micros` value could be >>> encoded >>> as an RFC3339 string, so perhaps that should be allowed for, but maybe >>> that's a step too far. >>> >>> I think logical types should should stay above the encoding/decoding… >>> With timestamp-micros we could extend it to make it applicable to string >>> and implement the converters, and then in json you would have something >>> readable, but you would then have the same in binary and pay the >>> readability cost there as well. >>> >> >> I'm not sure what you mean there. I wouldn't expect the Avro binary >> format to be readable at all. >> >> I implemented special handling for decimal logical type in my >>> encoder/decoder, but the best implementation I could do still feels like a >>> hack... >>> >>> >>> - I wonder if there should be some indication of version so that you >>> know which JSON encoding version you're reading. Perhaps the Avro schema >>> could include a version field (maybe as part of a definition) so you know >>> which version of the spec to use when encoding/decoding. Then bet-hedging >>> wouldn't be quite as important. >>> >>> I think Schema needs to stay decoupled from the encoding. The same >>> schema can be encoded in various ways (I have a csv encoder/decoder for >>> example, https://demo.spf4j.org/example/records?_Accept=text/csv ). >>> I think the right abstraction for what you are looking for is the Media >>> Type(https://en.wikipedia.org/wiki/Media_type ), >>> It would be helpful to “standardize” the media types for the avro >>> encodings: >>> >> >> Yes, on reflection, I agree, even though not every possible medium has a >> media type. For example, what if we're storing JSON data in a file? I guess >> it would be up to us to store the type along with the data, as the registry >> message wire format >> <https://docs.confluent.io/current/schema-registry/serializer-formatter.html#wire-format> >> does, for example by wrapping the entire value in another JSON object. >> >> >>> Here is what I mean, (with some examples where the same schema is served >>> with different encodings): >>> >>> 1) Binary: “application/avro” >>> https://demo.spf4j.org/example/records?_Accept=application/avro >>> 2) Current Json: “application/avro+json" >>> https://demo.spf4j.org/example/records?_Accept=application/avro-x%2Bjson >>> <https://demo.spf4j.org/example/records?_Accept=application/avro+json> >>> 3) New Json: “application/avro-x+json” ? >>> https://demo.spf4j.org/example/records?_Accept=application/avro-x%2Bjson >>> <https://demo.spf4j.org/example/records?_Accept=application/avro+json> >>> >> >> ISTM that "x" isn't a hugely descriptive qualifier there. How about >> "application/avro+json.v2" ? Then it's clear what to do if we want to make >> another version. >> >> >> >>> The media type including the avro schema (like you can see in the >>> response ContentType in the headers above) can provide complete type >>> information to be able to read a avro object from a byte stream. >>> >>> >>> application/avro-x+json;avsc="{\"type\":\"array\",\"items\":{\"$ref\":\"org.spf4j.demo:jaxrs-spf4j-demo-schema:0.8:b\"}}” >>> >>> In HTTP context this fits well with content negotiation, and a client >>> can ask for a previous version like: >>> >>> >>> https://demo.spf4j.org/example/records/1?_Accept=application/json;avsc=%22{\%22$ref\%22:\%22org.spf4j.demo:jaxrs-spf4j-demo-schema:0.4:b\%22}%22 >>> <https://demo.spf4j.org/example/records/1?_Accept=application/json;avsc=%22%7B%5C%22$ref%5C%22:%5C%22org.spf4j.demo:jaxrs-spf4j-demo-schema:0.4:b%5C%22%7D%22> >>> >>> >> >>> Note on $ref, it is an extension to avsc I use to reference schemas >>> from maven repos. (see >>> https://github.com/zolyfarkas/jaxrs-spf4j-demo/wiki/AvroReferences if >>> interested in more detail) >>> >> >> Interesting stuff. I like the idea of being able to get the server to >> check the desired client encoding, although I'm somewhat wary of the >> potential security implications of $ref with arbitrary URLs. >> >> Apart from the issues you raised, does my description of the proposed >> semantics seem reasonable? It could be slightly cleverer and avoid >> type-name wrapping in more situations, but this seemed like a nice balance >> between easy-to-explain and idiomatic-in-most-situations. >> >> cheers, >> rog. >> >> >> >
