ConcurrentModificationException using new Startable.dependsOn(startable)

I ran into an error in one of my TravisCI builds using the new dependsOn mechanism:

    13780 ERROR 🐳 [postgres:9.6.12]  - Could not start container
    java.util.ConcurrentModificationException
    	at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1660)
    	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
    	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
    	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:550)
    	at java.base/java.util.stream.AbstractPipeline.evaluateToArrayNode(AbstractPipeline.java:260)
    	at java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:517)
    	at org.testcontainers.containers.GenericContainer.applyConfiguration(GenericContainer.java:510)
    	at org.testcontainers.containers.GenericContainer.tryStart(GenericContainer.java:301)
    	at org.testcontainers.containers.GenericContainer.lambda$doStart$0(GenericContainer.java:285)
    	at org.rnorth.ducttape.unreliables.Unreliables.retryUntilSuccess(Unreliables.java:81)
    	at org.testcontainers.containers.GenericContainer.doStart(GenericContainer.java:283)
    	at org.testcontainers.containers.GenericContainer.start(GenericContainer.java:272)
    	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
    	at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1654)
    	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
    	at java.base/java.util.stream.ForEachOps$ForEachTask.compute(ForEachOps.java:290)
    	at java.base/java.util.concurrent.CountedCompleter.exec(CountedCompleter.java:746)
    	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
    	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
    	at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
    	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
    	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:177)

My containers are defined like this:

	@Container
	public static PostgreSQLContainer<?> postgres = new PostgreSQLContainer<>()
					.withNetworkAliases("testpostgres")
					.withDatabaseName("testdb");
	
    @Container
    public static MicroProfileApplication<?> app = new MicroProfileApplication<>()
                    .withEnv("POSTGRES_HOSTNAME", "testpostgres")
                    .withEnv("POSTGRES_PORT", "5432")
                    .withAppContextRoot("/myservice")
                    .dependsOn(postgres);

Using the latest version of testcontainers (1.12.0), the exception lines up with this bit of code:

    private void applyConfiguration(CreateContainerCmd createCommand) {
        HostConfig hostConfig = buildHostConfig();
        createCommand.withHostConfig(hostConfig);

        // Set up exposed ports (where there are no host port bindings defined)
        ExposedPort[] portArray = exposedPorts.stream()
                .map(ExposedPort::new)
                .toArray(ExposedPort[]::new);  // << --- CONCURRENT MOD EX HERE

It should also be noted that I am starting my containers in parallel like this:

containersToStart.parallelStream().forEach(GenericContainer::start);

which should be OK, since I believe the main value of dependsOn is that it allows us to do parallel container start without needing to worry about dependencies.

Inizia in GenericContainer.applyConfiguration, nello stream exposedPorts, quindi segui i percorsi dependsOn e GenericContainer.start paralleli mostrati nel report. Riproduci la configurazione PostgreSQL/applicazione con containersToStart.parallelStream().forEach(GenericContainer::start) e considera l’issue completata quando i container dipendenti si avviano senza ConcurrentModificationException.