Also, as for the backwards compatibility discussion, I don't believe non-portable jobs will be able to be upgraded to portable jobs and hence may be a good time to make upgrade incompatible coder changes at that point in time.
On Fri, Apr 5, 2019 at 1:44 PM Lukasz Cwik <lc...@google.com> wrote: > Robert, I filed https://issues.apache.org/jira/browse/BEAM-7015 for > removing the Python SDK copy of standard_coders.yaml and assigned it to you. > > On Fri, Apr 5, 2019 at 9:24 AM Kenneth Knowles <k...@apache.org> wrote: > >> Nested and unnested contexts are two different encodings. Can we just >> give them different URNs? We can even just express the length-prefixed >> UTF-8 as a composition of the length-prefix URN and the UTF-8 URN. >> >> On Fri, Apr 5, 2019 at 12:38 AM Robert Bradshaw <rober...@google.com> >> wrote: >> >>> On Fri, Apr 5, 2019 at 12:50 AM Heejong Lee <heej...@google.com> wrote: >>> > >>> > Robert, does nested/unnested context work properly for Java? >>> >>> I believe so. It is similar to the bytes coder, that prefixes vs. not >>> based on the context. >>> >>> > I can see that the Context is fixed to NESTED[1] and the encode method >>> with the Context parameter is marked as deprecated[2]. >>> > >>> > [1]: >>> https://github.com/apache/beam/blob/0868e7544fd1e96db67ff5b9e70a67802c0f0c8e/sdks/java/core/src/main/java/org/apache/beam/sdk/coders/StringUtf8Coder.java#L68 >>> > [2]: >>> https://github.com/apache/beam/blob/0868e7544fd1e96db67ff5b9e70a67802c0f0c8e/sdks/java/core/src/main/java/org/apache/beam/sdk/coders/Coder.java#L132 >>> >>> That doesn't mean it's unused, e.g. >>> >>> >>> https://github.com/apache/beam/blob/release-2.12.0/sdks/java/core/src/main/java/org/apache/beam/sdk/util/CoderUtils.java#L160 >>> >>> https://github.com/apache/beam/blob/release-2.12.0/sdks/java/core/src/main/java/org/apache/beam/sdk/coders/LengthPrefixCoder.java#L64 >>> >>> (and I'm sure there's others). >>> >>> > On Thu, Apr 4, 2019 at 3:25 PM Robert Bradshaw <rober...@google.com> >>> wrote: >>> >> >>> >> I don't know why there are two separate copies of >>> >> standard_coders.yaml--originally there was just one (though it did >>> >> live in the Python directory). I'm guessing a copy was made rather >>> >> than just pointing both to the new location, but that completely >>> >> defeats the point. I can't seem to access JIRA right now; could >>> >> someone file an issue to resolve this? >>> >> >>> >> I also think the spec should be next to the definition of the URN, >>> >> that's one of the reason the URNs were originally in a markdown file >>> >> (to encourage good documentation, literate programming style). Many >>> >> coders already have their specs there. >>> >> >>> >> Regarding backwards compatibility, we can't change existing coders, >>> >> and making new coders won't help with inference ('cause changing that >>> >> would also be backwards incompatible). Fortunately, I think we're >>> >> already doing the consistent thing here: In both Python and Java the >>> >> raw UTF-8 encoded bytes are encoded when used in an *unnested* context >>> >> and the length-prefixed UTF-8 encoded bytes are used when the coder is >>> >> used in a *nested* context. >>> >> >>> >> I'd really like to see the whole nested/unnested context go away, but >>> >> that'll probably require Beam 3.0; it causes way more confusion than >>> >> the couple of bytes it saves in a couple of places. >>> >> >>> >> - Robert >>> >> >>> >> On Thu, Apr 4, 2019 at 10:55 PM Robert Burke <rob...@frantil.com> >>> wrote: >>> >> > >>> >> > My 2cents is that the "Textual description" should be part of the >>> documentation of the URNs on the Proto messages, since that's the common >>> place. I've added a short description for the varints for example, and we >>> already have lenghthier format & protocol descriptions there for iterables >>> and similar. >>> >> > >>> >> > The proto [1] *can be* the spec if we want it to be. >>> >> > >>> >> > [1]: >>> https://github.com/apache/beam/blob/069fc3de95bd96f34c363308ad9ba988ab58502d/model/pipeline/src/main/proto/beam_runner_api.proto#L557 >>> >> > >>> >> > On Thu, 4 Apr 2019 at 13:51, Kenneth Knowles <k...@apache.org> >>> wrote: >>> >> >> >>> >> >> >>> >> >> >>> >> >> On Thu, Apr 4, 2019 at 1:49 PM Robert Burke <rob...@frantil.com> >>> wrote: >>> >> >>> >>> >> >>> We should probably move the "java" version of the yaml file [1] >>> to a common location rather than deep in the java hierarchy, or copying it >>> for Go and Python, but that can be a separate task. It's probably >>> non-trivial since it looks like it's part of a java resources structure. >>> >> >> >>> >> >> >>> >> >> Seems like /model is a good place for this if we don't want to >>> invent a new language-independent hierarchy. >>> >> >> >>> >> >> Kenn >>> >> >> >>> >> >> >>> >> >>> >>> >> >>> Luke, the Go SDK doesn't currently do this validation, but it >>> shouldn't be difficult, given pointers to the Java and Python variants of >>> the tests to crib from [2]. Care would need to be taken so that Beam Go SDK >>> users (such as they are) aren't forced to run them, and not have the yaml >>> file to read. I'd suggest putting it with the integration tests [3]. >>> >> >>> >>> >> >>> I've filed a JIRA (BEAM-7009) for tracking this Go SDK side work. >>> [4] >>> >> >>> >>> >> >>> 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/search?q=standard_coders.yaml&unscoped_q=standard_coders.yaml >>> >> >>> 3: https://github.com/apache/beam/tree/master/sdks/go/test >>> >> >>> 4: https://issues.apache.org/jira/browse/BEAM-7009 >>> >> >>> >>> >> >>> >>> >> >>> On Thu, 4 Apr 2019 at 13:28, Lukasz Cwik <lc...@google.com> >>> wrote: >>> >> >>>> >>> >> >>>> >>> >> >>>> >>> >> >>>> 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, >>> >>
