A potential breaking change would be the case when Java 8 support module hasn't been registered and Jackson seems to serialize and de-serialize the objects successfully, but with a obscure JSON structure.
Jackson 2.12 introduced a solution to prevent this from happening for Java 8 date/time types. (Jackson change: https://github.com/FasterXML/jackson-databind/issues/2683) Jackson 2.12 was first used in Pulsar 2.8.0 (Jackson upgrade 2.11 -> 2.12 in https://github.com/apache/pulsar/pull/10782). If you try to use Java 8 date/time types with Jackson, you will get this exception unless the Java 8 support modules are registered: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Java 8 date/time type `java.time.Instant` not supported by default: add Module "com.fasterxml.jackson.datatype:jackson-datatype-jsr310" to enable handling An example where Jackson doesn't fail at serialization time, is the usage of java.util.Optional . However, the value doesn't get serialized at all and deserialization fails. The risk of this being a breaking change is low since there doesn't seem to be cases where serialization and de-serialization would work without the Java 8 support modules using a bad JSON structure. > Context question since I'm not familiar with functions: How does a function > author use Jackson provided by Pulsar? Why does pulsar provide Jackson to > function? The Pulsar Functions will use JSON serialization/deserialization by default. (documented in https://pulsar.apache.org/docs/2.10.x/functions-develop/#serde ). The runtime uses Jackson for this purpose. -Lari On 2023/01/17 07:01:13 Asaf Mesika wrote: > Can the scenarios of breaking changes for users be described in the PIP if > they exist? If this is a breaking change, it might be a good thing to point > it out in the PIP and in the release notes ("If you did this, then perhaps > you want to do that"). > > Context question since I'm not familiar with functions: How does a function > author use Jackson provided by Pulsar? Why does pulsar provide Jackson to > function? > > > On Mon, Jan 16, 2023 at 12:12 PM Lari Hotari <lhot...@apache.org> wrote: > > > I created PIP-243, https://github.com/apache/pulsar/issues/19243 . Since > > this is already discussed in this thread, I'll open it directly for voting. > > > > -Lari > > > > On 2023/01/09 11:05:35 Lari Hotari wrote: > > > Hi all, > > > > > > Jackson has a separate Java 8 support modules for adding support for > > proper serialization and deserialization of new classes that were added in > > Java 8 (Java 8 was released in 2014). > > > > > > These Jackson Java 8 support modules haven't been used in the Pulsar > > code base. This is a pity. This causes a lot of pain when using Java Time > > classes in Pulsar applications or Pulsar Functions. There are ways to get > > the classes working for applications, but the documentation is missing. It > > would make things easier if the Java 8 support modules for Jackson would be > > included and registered by default. > > > > > > I have created a PR to register Jackson Java 8 support modules by > > default for all Pulsar components. The PR is > > https://github.com/apache/pulsar/pull/19161 . > > > > > > Please review and provide feedback. Do we need a PIP for this change? > > > > > > -Lari > > > > > >
