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,
