Sorry but I'm afraid I'm not understanding well the scenario... What's
the point on keeping a reference of the serialized class if
AVRO/Protobuf are using schemas?
I mean, I've understood that AVRO and Protobuf follow schemas in order
to serialize/deserialize an object in a binary way. So I'd expect to
have following things saved into the checkpoint:
- AVRO/Protobuf schema of the serialized object stored in JSON or
using Java serialization mechanism
- Object binary serialized according to the schema
So, then, when the checkpoint is going to be restored, it checks if new
generated schema, from object to be restored, is compatible with the
old one, and, if it is compatible, then just read its schema+binary
data saved into the checkpoint restoring the object.
Is not like that?
Also I don't understand when you said that a reference to the Beam
Coder is saved into the checkpoint, because the error I'm getting is
referencing the java model class ("Caused by:
java.io.InvalidClassException: internal.model.dimension.POJOModel;
local class incompatible: stream classdesc serialVersionUID =
-223148029368332375, local class serialVersionUID =
4489864664852536553"), not the coder itself.
Thanks
On Thu, 2020-06-04 at 18:40 +0200, Maximilian Michels wrote:
> I was under the assumption that this should work but ProtoCoder keeps
> a
> reference of the class used to serialize. That causes the snapshot to
> break.
>
> We can fix this by:
>
> a) writing/using coders which do not keep instances of evolving
> classes
> b) adding an interface to Beam for Coder
> serialization/deserialization
> c) adding a mode to Flink which allows to use newly supplied coders
> instead of having to load the old coder
>
> From all the options (a) is the most feasible for you. It looks like
> neither ProtoCoder nor AvroCoder fall into this category.
>
> -Max
>
> On 04.06.20 16:22, Ivan San Jose wrote:
> > I've changed my Java model in order to use ProtoCoder (with
> > @DefaultCoder(ProtoCoder.class)), but I'm getting same error when
> > tryingto restore the last taken checkpoint after adding an
> > attribute to
> > that model.
> >
> > What do you think it could happen? It seems that state saved within
> > the
> > checkpoint is still using Java serialization mechanism...
> >
> > On Thu, 2020-06-04 at 13:05 +0000, Ivan San Jose wrote:
> > > Thanks Max for your response. I'd try with AvroCoder then. But I
> > > still
> > > have a question, I guess AvroCoder is generating the AVRO schema
> > > using
> > > Java reflection, and then that generated schema is saved within
> > > the
> > > Flink checkpoint, right?
> > >
> > > On Wed, 2020-06-03 at 18:00 +0200, Maximilian Michels wrote:
> > > > Hi Ivan,
> > > >
> > > > Moving to the new type serializer snapshot interface is not
> > > > going
> > > > to
> > > > solve this problem because we cannot version the coder through
> > > > the
> > > > Beam
> > > > coder interface. That is only possible through Flink. However,
> > > > it
> > > > is
> > > > usually not trivial.
> > > >
> > > > In Beam, when you evolve your data model, the only way you can
> > > > maintain
> > > > compatible is to use a serialization format which can evolve,
> > > > e.g.
> > > > KafkaIO or Protobuf.
> > > >
> > > > Cheers,
> > > > Max
> > > >
> > > > On 03.06.20 16:47, Ivan San Jose wrote:
> > > > > Hi, we have a Beam application running with Flink runner and
> > > > > we
> > > > > are
> > > > > struggling using Flink checkpoints. Everytime we evolve the
> > > > > source
> > > > > code
> > > > > modifying a Java model, an exception is thrown when trying to
> > > > > restore
> > > > > last checkpoint taken:
> > > > >
> > > > > Caused by: java.lang.IllegalStateException: Could not Java-
> > > > > deserialize
> > > > > TypeSerializer while restoring checkpoint metadata for
> > > > > serializer
> > > > > snapshot
> > > > > 'org.apache.beam.runners.flink.translation.types.CoderTypeSer
> > > > > iali
> > > > > ze
> > > > > r$Le
> > > > > gacySnapshot'. Please update to the TypeSerializerSnapshot
> > > > > interface
> > > > > that removes Java Serialization to avoid this problem in the
> > > > > future.
> > > > > at
> > > > > org.apache.flink.api.common.typeutils.TypeSerializerConfigSna
> > > > > psho
> > > > > t.
> > > > > rest
> > > > > oreSerializer(TypeSerializerConfigSnapshot.java:138)
> > > > > at
> > > > > org.apache.flink.runtime.state.StateSerializerProvider.previo
> > > > > usSc
> > > > > he
> > > > > maSe
> > > > > rializer(StateSerializerProvider.java:189)
> > > > > at
> > > > > org.apache.flink.runtime.state.StateSerializerProvider.curren
> > > > > tSch
> > > > > em
> > > > > aSer
> > > > > ializer(StateSerializerProvider.java:164)
> > > > > at
> > > > > org.apache.flink.runtime.state.RegisteredOperatorStateBackend
> > > > > Meta
> > > > > In
> > > > > fo.g
> > > > > etPartitionStateSerializer(RegisteredOperatorStateBackendMeta
> > > > > Info
> > > > > .j
> > > > > ava:
> > > > > 113)
> > > > > at
> > > > > org.apache.flink.runtime.state.OperatorStateRestoreOperation.
> > > > > rest
> > > > > or
> > > > > e(Op
> > > > > eratorStateRestoreOperation.java:94)
> > > > > at
> > > > > org.apache.flink.runtime.state.DefaultOperatorStateBackendBui
> > > > > lder
> > > > > .b
> > > > > uild
> > > > > (DefaultOperatorStateBackendBuilder.java:83)
> > > > > ... 12 more
> > > > > Caused by: java.io.InvalidClassException:
> > > > > internal.model.dimension.Dimension; local class incompatible:
> > > > > stream
> > > > > classdesc serialVersionUID = -223148029368332375, local class
> > > > > serialVersionUID = 4489864664852536553
> > > > >
> > > > > As you can see the exception is complaining about class was
> > > > > evolved
> > > > > and
> > > > > they are not compatible any more.
> > > > >
> > > > > After checking some documentation and Beam source code...
> > > > > https://flink.apache.org/ecosystem/2020/02/22/apache-beam-how-beam-runs-on-top-of-flink.html
> > > > > (Serializers
> > > > > vs
> > > > > Coders)
> > > > > https://github.com/apache/beam/blob/785609f22d013411b7973bbf9e2d15c3c8171fb2/runners/flink/1.8/src/main/java/org/apache/beam/runners/flink/translation/types/CoderTypeSerializer.java
> > > > >
> > > > > It seems that Beam coders are wrapped into Flink's
> > > > > TypeSerializers,
> > > > > and, at the end, Beam coders are the ones in charge of
> > > > > serialize/deserialize objects.
> > > > >
> > > > > Also reading
> > > > > https://ci.apache.org/projects/flink/flink-docs-release-1.10/dev/stream/state/custom_serialization.html#migrating-from-deprecated-serializer-snapshot-apis-before-flink-17
> > > > > , and seeing CoderTyperSerializer implementation it seems
> > > > > Beam is
> > > > > implementing a deprecated interface and should be moved to
> > > > > new
> > > > > TypeSerializerSnapshot one. To be honest I don't know if that
> > > > > would
> > > > > solve my problem, but the exception is clearly saying "Please
> > > > > update to
> > > > > the TypeSerializerSnapshot interface that removes Java
> > > > > Serialization to
> > > > > avoid this problem in the future.", so I gues would solve it.
> > > > >
> > > > > Can someone help me here? I could try to update the
> > > > > implementation
> > > > > if
> > > > > someone give me some hints, because right now I'm a little
> > > > > bit
> > > > > lost.
> > > > >
> > > > > Thanks
> > > > >
> > > > >
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