Thebas opened a new issue, #2406:
URL: https://github.com/apache/incubator-kie-issues/issues/2406
### Component
Drools
### Versions
- Drools: 10.2.0
- Java: 21 runtime (locally 21.0.2); Maven compilation target 17
- Spring Boot: 3.5.16
- Maven: 3.9.16 (locally installed)
### Problem
`PhreakFromNode.doLeftDeletes` removes the staged left tuple from the from
node's
left tuple memory unconditionally:
```java
for (TupleImpl leftTuple = srcLeftTuples.getDeleteFirst(); leftTuple !=
null; ) {
TupleImpl next = leftTuple.getStagedNext();
ltm.remove(leftTuple);
```
When the tuple is not in that memory — it was staged and never actually
added, or
it was already removed — org.drools.base.util.LinkedList.remove() misses
both the
firstNode and lastNode branches, falls into the middle-node branch and
dereferences a null previous:
java.lang.NullPointerException: Cannot invoke
"org.drools.core.util.DoubleLinkedEntry.setNext(org.drools.core.util.SingleLinkedEntry)"
because the return value of
"org.drools.core.util.DoubleLinkedEntry.getPrevious()" is null
at org.drools.core.util.LinkedList.remove(LinkedList.java:178)
at org.drools.core.util.index.TupleList.remove(TupleList.java:51)
at
org.drools.core.phreak.PhreakFromNode.doLeftDeletes(PhreakFromNode.java:207)
at org.drools.core.phreak.PhreakFromNode.doNode(PhreakFromNode.java:64)
at
org.drools.core.phreak.RuleNetworkEvaluatorImpl.evaluateNonBetaNonTerminalNode(RuleNetworkEvaluatorImpl.java:405)
at
org.drools.core.phreak.RuleNetworkEvaluatorImpl.evaluateNonTerminalNode(RuleNetworkEvaluatorImpl.java:385)
at
org.drools.core.phreak.RuleNetworkEvaluatorImpl.innerEval(RuleNetworkEvaluatorImpl.java:318)
at
org.drools.core.phreak.RuleNetworkEvaluatorImpl.outerEval(RuleNetworkEvaluatorImpl.java:250)
at
org.drools.core.phreak.RuleNetworkEvaluatorImpl.evaluateNetwork(RuleNetworkEvaluatorImpl.java:142)
at
org.drools.core.phreak.RuleExecutor.evaluateNetwork(RuleExecutor.java:225)
at
org.drools.core.phreak.RuleExecutor.evaluateNetworkIfDirty(RuleExecutor.java:236)
at
org.drools.core.phreak.RuleExecutor.evaluateNetworkAndFire(RuleExecutor.java:85)
at
org.drools.core.concurrent.AbstractGroupEvaluator.evaluateAndFire(AbstractGroupEvaluator.java:53)
at
org.drools.kiesession.agenda.DefaultAgenda.fireLoop(DefaultAgenda.java:616)
at
org.drools.kiesession.agenda.DefaultAgenda.internalFireAllRules(DefaultAgenda.java:569)
at
org.drools.kiesession.agenda.DefaultAgenda.fireAllRules(DefaultAgenda.java:561)
at
org.drools.kiesession.session.StatefulKnowledgeSessionImpl.internalFireAllRules(StatefulKnowledgeSessionImpl.java:1110)
at
org.drools.kiesession.session.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1101)
Seen in production on a stateful KieSession driving fireAllRules() from a
Kafka
listener, with rules using from. The session is serialised behind a write
lock, so
the insert/fire path is single threaded.
PhreakFromNode is the only Phreak node that does not guard this call. Every
other
one does, with the same comment:
┌───────────────────────────────────┐
│ Node │
Guard │
├───────────────────────────────────┤
│ PhreakJoinNode:409 │ if
(leftTuple.getMemory() != null) │
├───────────────────────────────────┤
│ PhreakNotNode:446 │ if
(leftTuple.getMemory() != null) │
├───────────────────────────────────┤
│ PhreakExistsNode:432 │ if
(leftTuple.getMemory() != null) │
├───────────────────────────────────┤
│ PhreakAccumulateNode:556 │ if (leftTuple.getMemory() !=
null) │
├───────────────────────────────────┤
│ PhreakSubnetworkNotExistsNode:193 │ if (leftTuple.getMemory() != null) │
├───────────────────────────────────┤
│ PhreakNodeOperations:219, 240 │ if (leftTuple.getMemory() !=
null) │
├───────────────────────────────────┤
│ PhreakFromNode:207 │ missing
│
└───────────────────────────────────┘
PhreakReactiveFromNode extends PhreakFromNode and does not override
doLeftDeletes, so it has the same gap.
Expected behaviour
Deleting a left tuple that is not in the from node's left tuple memory is a
no-op, as
it is on every other Phreak node — not an NPE that aborts fireAllRules() and
leaves
the session in an undefined state.
Related
RuleExecutorDormantTupleTest / issue #6422 is the same failure mode
(LinkedList.remove on a tuple that is already unlinked) in RuleExecutor.
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