On Thu, Apr 4, 2019 at 1:15 PM Chamikara Jayalath <chamik...@google.com> wrote:
> > > On Thu, Apr 4, 2019 at 12:15 PM Lukasz Cwik <lc...@google.com> wrote: > >> standard_coders.yaml[1] is where we are currently defining these formats. >> Unfortunately the Python SDK has its own copy[2]. >> > > Ah great. Thanks for the pointer. Any idea why there's a separate copy > for Python ? I didn't see a significant difference in definitions looking > at few random coders there but I might have missed something. If there's no > reason to maintain two, we should probably unify. > Also, seems like we haven't added the definition for UTF-8 coder yet. > > Not certain as well. I did notice the timer coder definition didn't exist in the Python copy. > >> Here is an example PR[3] that adds the "beam:coder:double:v1" as tests to >> the Java and Python SDKs to ensure interoperability. >> >> Robert Burke, does the Go SDK have a test where it uses >> standard_coders.yaml and runs compatibility tests? >> >> Chamikara, creating new coder classes is a pain since the type -> coder >> mapping per SDK language would select the non-well known type if we added a >> new one to a language. If we swapped the default type->coder mapping, this >> would still break update for pipelines forcing users to update their code >> to select the non-well known type. If we don't change the default >> type->coder mapping, the well known coder will gain little usage. I think >> we should fix the Python coder to use the same encoding as Java for UTF-8 >> strings before there are too many Python SDK users. >> > > I was thinking that may be we should just change the default UTF-8 coder > for Fn API path which is experimental. Updating Python to do what's done > for Java is fine if we agree that encoding used for Java should be the > standard. > > That is a good idea to use the Fn API experiment to control which gets selected. > >> 1: >> https://github.com/apache/beam/blob/master/model/fn-execution/src/main/resources/org/apache/beam/model/fnexecution/v1/standard_coders.yaml >> 2: >> https://github.com/apache/beam/blob/master/sdks/python/apache_beam/testing/data/standard_coders.yaml >> 3: https://github.com/apache/beam/pull/8205 >> >> On Thu, Apr 4, 2019 at 11:50 AM Chamikara Jayalath <chamik...@google.com> >> wrote: >> >>> >>> >>> On Thu, Apr 4, 2019 at 11:29 AM Robert Bradshaw <rober...@google.com> >>> wrote: >>> >>>> A URN defines the encoding. >>>> >>>> There are (unfortunately) *two* encodings defined for a Coder (defined >>>> by a URN), the nested and the unnested one. IIRC, in both Java and >>>> Python, the nested one prefixes with a var-int length, and the >>>> unnested one does not. >>>> >>> >>> Could you clarify where we define the exact encoding ? I only see a URN >>> for UTF-8 [1] while if you look at the implementations Java includes length >>> in the encoding [1] while Python [1] does not. >>> >>> [1] >>> https://github.com/apache/beam/blob/069fc3de95bd96f34c363308ad9ba988ab58502d/model/pipeline/src/main/proto/beam_runner_api.proto#L563 >>> [2] >>> https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/coders/StringUtf8Coder.java#L50 >>> [3] >>> https://github.com/apache/beam/blob/master/sdks/python/apache_beam/coders/coders.py#L321 >>> >>> >>> >>>> >>>> We should define the spec clearly and have cross-language tests. >>>> >>> >>> +1 >>> >>> Regarding backwards compatibility, I agree that we should probably not >>> update existing coder classes. Probably we should just standardize the >>> correct encoding (may be as a comment near corresponding URN in the >>> beam_runner_api.proto ?) and create new coder classes as needed. >>> >>> >>>> >>>> On Thu, Apr 4, 2019 at 8:13 PM Pablo Estrada <pabl...@google.com> >>>> wrote: >>>> > >>>> > Could this be a backwards-incompatible change that would break >>>> pipelines from upgrading? If they have data in-flight in between operators, >>>> and we change the coder, they would break? >>>> > I know very little about coders, but since nobody has mentioned it, I >>>> wanted to make sure we have it in mind. >>>> > -P. >>>> > >>>> > On Wed, Apr 3, 2019 at 8:33 PM Kenneth Knowles <k...@apache.org> >>>> wrote: >>>> >> >>>> >> Agree that a coder URN defines the encoding. I see that string UTF-8 >>>> was added to the proto enum, but it needs a written spec of the encoding. >>>> Ideally some test data that different languages can use to drive compliance >>>> testing. >>>> >> >>>> >> Kenn >>>> >> >>>> >> On Wed, Apr 3, 2019 at 6:21 PM Robert Burke <rob...@frantil.com> >>>> wrote: >>>> >>> >>>> >>> String UTF8 was recently added as a "standard coder " URN in the >>>> protos, but I don't think that developed beyond Java, so adding it to >>>> Python would be reasonable in my opinion. >>>> >>> >>>> >>> The Go SDK handles Strings as "custom coders" presently which for >>>> Go are always length prefixed (and reported to the Runner as >>>> LP+CustomCoder). It would be straight forward to add the correct handling >>>> for strings, as Go natively treats strings as UTF8. >>>> >>> >>>> >>> >>>> >>> On Wed, Apr 3, 2019, 5:03 PM Heejong Lee <heej...@google.com> >>>> wrote: >>>> >>>> >>>> >>>> Hi all, >>>> >>>> >>>> >>>> It looks like UTF-8 String Coder in Java and Python SDKs uses >>>> different encoding schemes. StringUtf8Coder in Java SDK puts the varint >>>> length of the input string before actual data bytes however StrUtf8Coder in >>>> Python SDK directly encodes the input string to bytes value. For the last >>>> few weeks, I've been testing and fixing cross-language IO transforms and >>>> this discrepancy is a major blocker for me. IMO, we should unify the >>>> encoding schemes of UTF8 strings across the different SDKs and make it a >>>> standard coder. Any thoughts? >>>> >>>> >>>> >>>> Thanks, >>>> >>>
