CachingParanamer breaks java.io.Serializable

[cresny]

using v 2.7.2, trying to serialize an ObjectReader instance (used in a Flink serialized function), I get this error:

com.fasterxml.jackson.module.paranamer.shaded.CachingParanamer
java.io.NotSerializableException: com.fasterxml.jackson.module.paranamer.shaded.CachingParanamer

I have verified that the ObjectReader instance does serialize correctly id the DefaultScalaModule is not registered. Is there a workaround for this?

[cowtowncoder]

Probably won't make much difference, but the latest is 2.7.4, so might make sense to try it just to make sure.

As to problem itself, this would be Paranamer class, just shaded, which we can not do much about, at least directly. It would be necessary to know call/dependency graph. It looks like paranamer module uses CachingParanamer, so fix should probably go in there. I'll file a bug for the project, to see if it can be isolated and hopefully fixed.

Generally however it is often better to try to avoid getting Jackson's object mapper, reader or writer from getting in transitive closure that is serialized. If at all possible. It's still quite a bit of stuff to transfer, without much value (as long as it can be re-created by workers).

[cresny]

Thanks, I caught this at the end of the day, too brain-dead to realize it's an easy workaround in scala using @transient lazy val. So there's no urgency at least for me.

[cowtowncoder]

For what that is worth, it is fixed for paranamer module for next releases, (2.7.6 / 2.8.0) since mapper/reader/writer ought to remain serializable.