JpaSagaStore in conjunction with Jackson unable to properly store state - axon

Question

In a SpringBoot application, I have the following configuration:
axon:
axonserver:
servers: "${AXON_SERVER:localhost}"
serializer:
general: jackson
messages: jackson
events: jackson
logging.level:
org.axonframework.modelling.saga: debug
Downsizing the scenario to bare minimum, the relevant portion of Saga class:
#Slf4j
#Saga
#ProcessingGroup("AuctionEventManager")
public class AuctionEventManagerSaga {
#Autowired
private transient EventScheduler eventScheduler;
private ScheduleToken scheduleToken;
private Instant auctionTimerStart;
#StartSaga
#SagaEventHandler(associationProperty = "auctionEventId")
protected void on(final AuctionEventScheduled event) {
this.auctionTimerStart = event.getTimerStart();
// Cancel any pre-existing previous job, since the scheduling thread might be lost upon a crash/restart of JVM.
if (this.scheduleToken != null) {
this.eventScheduler.cancelSchedule(this.scheduleToken);
}
this.scheduleToken = this.eventScheduler.schedule(
this.auctionTimerStart,
AuctionEventStarted.builder()
.auctionEventId(event.getAuctionEventId())
.build()
);
}
#EndSaga
#SagaEventHandler(associationProperty = "auctionEventId")
protected void on(final AuctionEventStarted event) {
log.info(
"[AuctionEventManagerSaga] Current state: {scheduleToken={}, auctionTimerStart={}}",
this.scheduleToken,
this.auctionTimerStart
);
}
}
In the final compiled class, we will end up having 4 properties: log (from #Slf4j), eventScheduler (transient, #Autowired), scheduleToken and auctionTimerStart.
For reference information, here is a sample of the general approach I've been using for both Command and Event classes:
#Value
#Builder
#JsonDeserialize(builder = AuctionEventStarted.AuctionEventStartedBuilder.class)
public class AuctionEventStarted {
AuctionEventId auctionEventId;
#JsonPOJOBuilder(withPrefix = "")
public static final class AuctionEventStartedBuilder {}
}
When executing the code, you get the following output:
2020-05-12 15:40:01.180 DEBUG 1 --- [mandProcessor-4] o.a.m.saga.repository.jpa.JpaSagaStore : Updating saga id c8aff7f7-d47f-4616-8a96-a40044cb7e3b as {}
As soon as the general serializer is changed to xstream, the content is serialized properly, but I face another issue during deserialization, since I have private static final class Builder classes using Lombok.
So is there a way for Axon to handle these scenarios:
1- Axon to safely manage Jackson to ignore #Autowired, transient and static properties from #Saga classes? I've attempted to manually define #JsonIgnore at non-state properties and it still didn't work.
2- Axon to safely configure XStream to ignore inner classes (mostly Builder classes implemented as private static final)?
Thanks in advance,
EDIT: I'm pursuing a resolution using my preferred serializer: JSON. I attempted to modify the saga class and extend JsonSerializer<AuctionEventManagerSaga>. For that I implemented the methods:
#Override
public Class<AuctionEventManagerSaga> handledType() {
return AuctionEventManagerSaga.class;
}
#Override
public void serialize(
final AuctionEventManagerSaga value,
final JsonGenerator gen,
final SerializerProvider serializers
) throws IOException {
gen.writeStartObject();
gen.writeObjectField("scheduleToken", value.eventScheduler);
gen.writeObjectField("auctionTimerStart", value.auctionTimerStart);
gen.writeEndObject();
}
Right now, I have something being serialized, but it has nothing to do with the properties I've defined:
2020-05-12 16:20:01.322 DEBUG 1 --- [mandProcessor-0] o.a.m.saga.repository.jpa.JpaSagaStore : Storing saga id c4b5d94c-7251-40a5-accf-332768b1cacd as {"delegatee":null,"unwrappingSerializer":false}
EDIT 2 Decided to add more insight into the issue I experience when I switch general to use XStream (even though it's somewhat unrelated to the main issue described in the title).
Here is the issue it complains to me:
2020-05-12 17:08:06.495 DEBUG 1 --- [ault-executor-0] o.a.a.c.command.AxonServerCommandBus : Received command response [message_identifier: "79631ffb-9a87-4224-bed3-a957730dced7"
error_code: "AXONIQ-4002"
error_message {
message: "No converter available\n---- Debugging information ----\nmessage : No converter available\ntype : jdk.internal.misc.InnocuousThread\nconverter : com.thoughtworks.xstream.converters.reflection.ReflectionConverter\nmessage[1] : Unable to make field private static final jdk.internal.misc.Unsafe jdk.internal.misc.InnocuousThread.UNSAFE accessible: module java.base does not \"opens jdk.internal.misc\" to unnamed module #7728643a\n-------------------------------"
location: "1#600b5b87a922"
details: "No converter available\n---- Debugging information ----\nmessage : No converter available\ntype : jdk.internal.misc.InnocuousThread\nconverter : com.thoughtworks.xstream.converters.reflection.ReflectionConverter\nmessage[1] : Unable to make field private static final jdk.internal.misc.Unsafe jdk.internal.misc.InnocuousThread.UNSAFE accessible: module java.base does not \"opens jdk.internal.misc\" to unnamed module #7728643a\n-------------------------------"
}
request_identifier: "2f7020b1-f655-4649-bbe0-d6f458b3c2f3"
]
2020-05-12 17:08:06.505 WARN 1 --- [ault-executor-0] o.a.c.gateway.DefaultCommandGateway : Command 'ACommandClassDispatchedFromSaga' resulted in org.axonframework.commandhandling.CommandExecutionException(No converter available
---- Debugging information ----
message : No converter available
type : jdk.internal.misc.InnocuousThread
converter : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
message[1] : Unable to make field private static final jdk.internal.misc.Unsafe jdk.internal.misc.InnocuousThread.UNSAFE accessible: module java.base does not "opens jdk.internal.misc" to unnamed module #7728643a
-------------------------------)
Still no luck on resolving this...

Answer 1

I've worked on Axon systems where the only used Serializer implementation was the JacksonSerializer too. Mind you though, this is not what the Axon team recommends. For messages (i.e. commands, events and queries) it makes perfect sense to use JSON as the serialized format. But switching the general Serializer to jackson means you have to litter your domain logic (e.g. your Saga) with Jackson specifics "to make it work".
Regardless, backtracking to my successful use case of jackson-serialized-sagas. In this case we used the correct match of JSON annotations on the fields we desired to take into account (the actual state) and to ignore the one's we didn't want deserialized (with either transient or #JsonIgnore). Why both do not seem to work in your scenario is not entirely clear at this stage.
What I do recall is that the referenced project's team very clearly decided against Lombok due to "overall weirdnes" when it comes to de-/serialization. As a trial it thus might be worth to not use any Lombok annotations/logic in the Saga class and see if you can de-/serialize it correctly in such a state.
If it does work at that moment, I think you have found your culprit for diving in further search.
I know this isn't an exact answer, but I hope it helps you regardless!
Might be worthwhile to share the repository where this problems occurs in; might make the problem clearer for others too.

Answer 2

I was able to resolve the issue #2 when using XStream as general serializer.
One of the Sagas had an #Autowired dependency property that was not transient.
XStream was throwing some cryptic message, but we managed to track the problem and address it.
As for JSON support, we had no luck. We ended up switched everything to XStream for now, as the company only uses Java and it would be ok to decode the events using XStream.
Not the greatest solution, as we really wanted (and hoped) JSON would be supported properly out of the box. Mind you, this is in conjunction with using Lombok which caused for the nuisance in this case.