I am writing a few integration tests for a flink job where each job creates a StreamExecutionEnvironment. At the end of each test, I close the streaming environment

env.close()

However, it seems like it is not releasing the memory. I am running the tests sequentially, where the first test runs followed by the second

When the second test runs I am getting the following error

2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]     10:18:54,057 ERROR org.apache.flink.core.memory.MemorySegmentFactory            [] - Cannot allocate direct memory segment java.lang.OutOfMemoryError: Direct buffer memory. The direct out-of-memory error has occurred. This can mean two things: either job(s) require(s) a larger size of JVM direct memory or there is a direct memory leak. The direct memory can be allocated by user code or some of its dependencies. In this case 'taskmanager.memory.task.off-heap.size' configuration option should be increased. Flink framework and its dependencies also consume the direct memory, mostly for network communication. The most of network memory is managed by Flink and should not result in out-of-memory error. In certain special cases, in particular for jobs with high parallelism, the framework may require more direct memory which is not managed by Flink. In this case 'taskmanager.memory.framework.off-heap.size' configuration option should be increased. If the error persists then there is probably a direct memory leak in user code or some of its dependencies which has to be investigated and fixed. The task executor has to be shutdown...
2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]          at java.base/java.nio.Bits.retryReserveMemoryLoop(Bits.java:251)
2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]          at java.base/java.nio.Bits.reserveMemory(Bits.java:205)
2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]          at java.base/java.nio.DirectByteBuffer.<init>(DirectByteBuffer.java:118)
2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]          at java.base/java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:317)
2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.core.memory.MemorySegmentFactory.allocateDirectMemory(MemorySegmentFactory.java:137)
2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.core.memory.MemorySegmentFactory.allocateUnpooledOffHeapMemory(MemorySegmentFactory.java:125)
2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.io.network.buffer.NetworkBufferPool.<init>(NetworkBufferPool.java:128)
2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.io.network.NettyShuffleServiceFactory.createNettyShuffleEnvironment(NettyShuffleServiceFactory.java:173)
2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.io.network.NettyShuffleServiceFactory.createNettyShuffleEnvironment(NettyShuffleServiceFactory.java:128)
2024-05-05T10:18:54.057-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.io.network.NettyShuffleServiceFactory.createNettyShuffleEnvironment(NettyShuffleServiceFactory.java:97)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.io.network.NettyShuffleServiceFactory.createShuffleEnvironment(NettyShuffleServiceFactory.java:78)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.io.network.NettyShuffleServiceFactory.createShuffleEnvironment(NettyShuffleServiceFactory.java:57)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.taskexecutor.TaskManagerServices.createShuffleEnvironment(TaskManagerServices.java:446)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.taskexecutor.TaskManagerServices.fromConfiguration(TaskManagerServices.java:304)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.taskexecutor.TaskManagerRunner.startTaskManager(TaskManagerRunner.java:631)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.minicluster.MiniCluster.startTaskManager(MiniCluster.java:755)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.minicluster.MiniCluster.startTaskManagers(MiniCluster.java:736)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.runtime.minicluster.MiniCluster.start(MiniCluster.java:457)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.client.program.PerJobMiniClusterFactory.submitJob(PerJobMiniClusterFactory.java:77)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.client.deployment.executors.LocalExecutor.execute(LocalExecutor.java:85)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.executeAsync(StreamExecutionEnvironment.java:2206)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.execute(StreamExecutionEnvironment.java:2093)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.streaming.api.environment.LocalStreamEnvironment.execute(LocalStreamEnvironment.java:68)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.execute(StreamExecutionEnvironment.java:2067)
2024-05-05T10:18:54.058-0700 [DEBUG] [TestEventLogger]          at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.execute(StreamExecutionEnvironment.java:2045)
2024-05-05T10:18:54.059-0700 [DEBUG] [TestEventLogger]          at com.Application.lambda$testExecution$3(Application.java:410)
2024-05-05T10:18:54.059-0700 [DEBUG] [TestEventLogger]          at java.base/java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1736)
2024-05-05T10:18:54.059-0700 [DEBUG] [TestEventLogger]          at java.base/java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1728)
2024-05-05T10:18:54.059-0700 [DEBUG] [TestEventLogger]          at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
2024-05-05T10:18:54.059-0700 [DEBUG] [TestEventLogger]          at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
2024-05-05T10:18:54.059-0700 [DEBUG] [TestEventLogger]          at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
2024-05-05T10:18:54.059-0700 [DEBUG] [TestEventLogger]          at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
2024-05-05T10:18:54.059-0700 [DEBUG] [TestEventLogger]          at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)

I don’t see those exceptions when I run them individually. So it seems like the first test is not releasing the direct memory allocated. How can I make sure that the tests release all the memory?