fix(server): tx leak when stopping the graph server

[hahahahbenny]

Purpose of the PR

• fix [Bug] tx leak when stopping server #2310

Main Changes

• I added two lines of code under the restoreTasks

        this.graph.graphTransaction().commit();
        this.graph.closeTx();

• added a concurrent set in the TinkerPopTransaction class to show which threads have not closed the transaction

  private final ConcurrentHashMap.KeySetView<String, Boolean> openedThreads =
                ConcurrentHashMap.newKeySet();

• insert key when open tx and remove key when close tx

       private void setOpened() {
            // The backend tx may be reused, here just set a flag
            assert !this.opened.get();
            this.opened.set(true);
            this.transactions.get().openedTime(DateUtil.now().getTime());
            this.openedThreads.add(Thread.currentThread().getName());
            this.refs.incrementAndGet();
        }

        private void setClosed() {
            // Just set flag opened=false to reuse the backend tx
            if (this.opened.get()) {
                this.opened.set(false);
                this.openedThreads.remove(Thread.currentThread().getName());
                this.refs.decrementAndGet();
            }
        }

• show threads have not close tx before E.checkState

        if(!this.tx.closed()){
            for (String key : this.tx.openedThreads) {
                LOG.warn("thread [{}] did not close transaction", key);
            }
        }
        E.checkState(this.tx.closed(),
                     "Ensure tx closed in all threads when closing graph '%s'",
                     this.name);

    }

Verifying these changes

• Trivial rework / code cleanup without any test coverage. (No Need)
• Already covered by existing tests, such as (please modify tests here).
• Need tests and can be verified as follows:
• add closetx under the restoreTasks , the shutdown log , did not warn Ensure tx closed in all threads when closing graph 'hugegraph'

2025-06-09 20:32:49 [gremlin-server-shutdown] [INFO] o.a.t.g.s.GremlinServer - Shutting down OpProcessor[]
2025-06-09 20:32:49 [gremlin-server-shutdown] [INFO] o.a.t.g.s.GremlinServer - Shutting down OpProcessor[cypher]
2025-06-09 20:32:49 [hugegraph-server-shutdown] [INFO] o.a.h.d.HugeGraphServer - HugeGraphServer stopping
2025-06-09 20:32:49 [gremlin-server-shutdown] [INFO] o.a.t.g.s.GremlinServer - Shutting down OpProcessor[session]
2025-06-09 20:32:49 [hugegraph-server-shutdown] [INFO] o.a.h.d.MemoryMonitor - Memory monitoring stopped.
2025-06-09 20:32:49 [gremlin-server-shutdown] [INFO] o.a.t.g.s.GremlinServer - Shutting down OpProcessor[traversal]
2025-06-09 20:32:49 [gremlin-server-shutdown] [INFO] o.a.t.g.s.GremlinServer - Shutting down thread pools.
2025-06-09 20:32:49 [gremlin-server-stop] [INFO] o.a.t.g.s.GremlinServer - Executing shutdown LifeCycleHook
2025-06-09 20:32:49 [gremlin-server-stop] [INFO] o.a.t.g.s.GremlinServer - Executed once at shutdown of Gremlin Server.
2025-06-09 20:32:51 [gremlin-server-stop] [INFO] o.a.h.StandardHugeGraph - Close graph standardhugegraph[hugegraph]
2025-06-09 20:32:51 [gremlin-server-stop] [INFO] o.a.h.t.ServerInfoManager - Remove server info: server-1
2025-06-09 20:32:51 [gremlin-server-stop] [INFO] o.a.t.g.s.GremlinServer - Closed Graph instance [hugegraph]
2025-06-09 20:32:51 [gremlin-server-stop] [INFO] o.a.t.g.s.GremlinServer - Gremlin Server - shutdown complete
2025-06-09 20:32:51 [hugegraph-server-shutdown] [INFO] o.a.h.d.HugeGraphServer - HugeGremlinServer stopped
2025-06-09 20:32:51 [hugegraph-server-shutdown] [INFO] o.a.h.d.HugeGraphServer - HugeRestServer stopped
2025-06-09 20:32:51 [hugegraph-server-shutdown] [INFO] o.a.h.HugeFactory - HugeFactory shutdown
2025-06-09 20:32:51 [hugegraph-server-shutdown] [INFO] o.a.h.d.HugeGraphServer - HugeGraph stopped
2025-06-09 20:32:51 [hugegraph-server-shutdown] [INFO] o.a.h.d.HugeGraphServer - HugeGraphServer stopped

• log show which thread have not closed tx

025-06-09 20:30:43 [gremlin-server-stop] [INFO] o.a.h.t.ServerInfoManager - Remove server info: server-1
2025-06-09 20:30:43 [gremlin-server-stop] [WARN] o.a.h.StandardHugeGraph - thread [main] did not close transaction
2025-06-09 20:30:43 [gremlin-server-stop] [WARN] o.a.t.g.s.GremlinServer - Exception while closing Graph instance [hugegraph]
java.lang.IllegalStateException: Ensure tx closed in all threads when closing graph 'hugegraph'
	at com.google.common.base.Preconditions.checkState(Preconditions.java:534) ~[guava-31.0.1-android.jar:?]
	at org.apache.hugegraph.util.E.checkState(E.java:64) ~[classes/:?]
	at org.apache.hugegraph.StandardHugeGraph.close(StandardHugeGraph.java:1011) ~[classes/:?]
	at org.apache.tinkerpop.gremlin.server.GremlinServer.lambda$null$7(GremlinServer.java:307) ~[gremlin-server-3.5.1.jar:3.5.1]
	at java.util.concurrent.ConcurrentHashMap$KeySetView.forEach(ConcurrentHashMap.java:4696) ~[?:?]
	at org.apache.tinkerpop.gremlin.server.GremlinServer.lambda$stop$8(GremlinServer.java:304) ~[gremlin-server-3.5.1.jar:3.5.1]
	at java.lang.Thread.run(Thread.java:829) [?:?]

Does this PR potentially affect the following parts?

• Dependencies (add/update license info & regenerate_known_dependencies.sh)
• Modify configurations
• The public API
• Other affects (standardHugeGraph)
• Nope

Documentation Status

• Doc - TODO
• Doc - Done
• Doc - No Need

[Copilot]

Pull Request Overview

This PR addresses a transaction leak by ensuring graph transactions are committed and closed after task restoration, tracking open threads, and warning if any threads leave transactions open at shutdown.

• Commit and close the graph transaction in restoreTasks to prevent TX leaks.
• Add a concurrent set to track threads that open transactions in TinkerPopTransaction.
• Log any threads with unclosed transactions before enforcing closure in StandardHugeGraph.close().

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
StandardTaskScheduler.java	Added calls to commit and close the transaction after restoring tasks.
StandardHugeGraph.java	Introduced openedThreads tracking, warning logs for unclosed threads, and a stricter check on TX closure.

Comments suppressed due to low confidence (2)

hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/task/StandardTaskScheduler.java:158

• Add unit or integration tests for restoreTasks to verify that transactions are correctly committed and closed, including failure scenarios during commit.

this.graph.graphTransaction().commit();

hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/StandardHugeGraph.java:1007

• [nitpick] The loop variable key is ambiguous; consider renaming it to threadName to clarify that it represents a thread identifier.

for (String key : this.tx.openedThreads) {

[imbajin]

THX