hi My Flink cluster uses S3 for storing the state backend. However, an exception occurs when the task runs for a long period of time. The content of the exception is "Timeout waiting for connection from pool". What could be the reason for this? The following is the specific error message. java.lang.Exception: Exception while creating StreamOperatorStateContext. at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:258) at org.apache.flink.streaming.api.operators.AbstractStreamOperator.initializeState(AbstractStreamOperator.java:256) at org.apache.flink.streaming.runtime.tasks.RegularOperatorChain.initializeStateAndOpenOperators(RegularOperatorChain.java:106) at org.apache.flink.streaming.runtime.tasks.StreamTask.restoreGates(StreamTask.java:753) at org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$1.call(StreamTaskActionExecutor.java:55) at org.apache.flink.streaming.runtime.tasks.StreamTask.restoreInternal(StreamTask.java:728) at org.apache.flink.streaming.runtime.tasks.StreamTask.restore(StreamTask.java:693) at org.apache.flink.runtime.taskmanager.Task.runWithSystemExitMonitoring(Task.java:953) at org.apache.flink.runtime.taskmanager.Task.restoreAndInvoke(Task.java:922) at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:746) at org.apache.flink.runtime.taskmanager.Task.run(Task.java:562) at java.base/java.lang.Thread.run(Thread.java:829) Caused by: org.apache.flink.util.FlinkException: Could not restore keyed state backend for KeyedProcessOperator_c82105323f1a61713019c6d1da10336c_(1/1) from any of the 1 provided restore options. at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:160) at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.keyedStatedBackend(StreamTaskStateInitializerImpl.java:355) at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:166) ... 11 more Caused by: org.apache.flink.runtime.state.BackendBuildingException: Caught unexpected exception. at org.apache.flink.contrib.streaming.state.RocksDBKeyedStateBackendBuilder.build(RocksDBKeyedStateBackendBuilder.java:407) at org.apache.flink.contrib.streaming.state.EmbeddedRocksDBStateBackend.createKeyedStateBackend(EmbeddedRocksDBStateBackend.java:513) at org.apache.flink.contrib.streaming.state.EmbeddedRocksDBStateBackend.createKeyedStateBackend(EmbeddedRocksDBStateBackend.java:100) at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.lambda$keyedStatedBackend$1(StreamTaskStateInitializerImpl.java:338) at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.attemptCreateAndRestore(BackendRestorerProcedure.java:168) at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:135) ... 13 more Caused by: java.io.IOException: com.amazonaws.SdkClientException: Unable to execute HTTP request: Timeout waiting for connection from pool at org.apache.flink.contrib.streaming.state.RocksDBStateDownloader.downloadDataForStateHandle(RocksDBStateDownloader.java:156) at org.apache.flink.contrib.streaming.state.RocksDBStateDownloader.lambda$null$0(RocksDBStateDownloader.java:115) at org.apache.flink.util.function.ThrowingRunnable.lambda$unchecked$0(ThrowingRunnable.java:49) at java.base/java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1736) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) ... 1 more Caused by: com.amazonaws.SdkClientException: Unable to execute HTTP request: Timeout waiting for connection from pool at com.amazonaws.http.AmazonHttpClient$RequestExecutor.handleRetryableException(AmazonHttpClient.java:1219) at com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeHelper(AmazonHttpClient.java:1165) at com.amazonaws.http.AmazonHttpClient$RequestExecutor.doExecute(AmazonHttpClient.java:814) at com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeWithTimer(AmazonHttpClient.java:781) at com.amazonaws.http.AmazonHttpClient$RequestExecutor.execute(AmazonHttpClient.java:755) at com.amazonaws.http.AmazonHttpClient$RequestExecutor.access$500(AmazonHttpClient.java:715) at com.amazonaws.http.AmazonHttpClient$RequestExecutionBuilderImpl.execute(AmazonHttpClient.java:697) at com.amazonaws.http.AmazonHttpClient.execute(AmazonHttpClient.java:561) at com.amazonaws.http.AmazonHttpClient.execute(AmazonHttpClient.java:541) at com.amazonaws.services.s3.AmazonS3Client.invoke(AmazonS3Client.java:5456) at com.amazonaws.services.s3.AmazonS3Client.invoke(AmazonS3Client.java:5403) at com.amazonaws.services.s3.AmazonS3Client.getObject(AmazonS3Client.java:1524) at com.facebook.presto.hive.s3.PrestoS3FileSystem$PrestoS3InputStream.lambda$openStream$2(PrestoS3FileSystem.java:1102) at com.facebook.presto.hive.RetryDriver.run(RetryDriver.java:139) at com.facebook.presto.hive.s3.PrestoS3FileSystem$PrestoS3InputStream.openStream(PrestoS3FileSystem.java:1099) at com.facebook.presto.hive.s3.PrestoS3FileSystem$PrestoS3InputStream.openStream(PrestoS3FileSystem.java:1084) at com.facebook.presto.hive.s3.PrestoS3FileSystem$PrestoS3InputStream.seekStream(PrestoS3FileSystem.java:1077) at com.facebook.presto.hive.s3.PrestoS3FileSystem$PrestoS3InputStream.lambda$read$1(PrestoS3FileSystem.java:1021) at com.facebook.presto.hive.RetryDriver.run(RetryDriver.java:139) at com.facebook.presto.hive.s3.PrestoS3FileSystem$PrestoS3InputStream.read(PrestoS3FileSystem.java:1020) at java.base/java.io.BufferedInputStream.read1(BufferedInputStream.java:290) at java.base/java.io.BufferedInputStream.read(BufferedInputStream.java:351) at java.base/java.io.DataInputStream.read(DataInputStream.java:149) at org.apache.flink.fs.s3presto.common.HadoopDataInputStream.read(HadoopDataInputStream.java:96) at java.base/java.io.InputStream.read(InputStream.java:205) at org.apache.flink.contrib.streaming.state.RocksDBStateDownloader.downloadDataForStateHandle(RocksDBStateDownloader.java:144) ... 6 more Suppressed: com.amazonaws.SdkClientException: Unable to execute HTTP request: Timeout waiting for connection from pool ... 32 more Caused by: org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.leaseConnection(PoolingHttpClientConnectionManager.java:316) at org.apache.http.impl.conn.PoolingHttpClientConnectionManager$1.get(PoolingHttpClientConnectionManager.java:282) at jdk.internal.reflect.GeneratedMethodAccessor58.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at com.amazonaws.http.conn.ClientConnectionRequestFactory$Handler.invoke(ClientConnectionRequestFactory.java:70) at com.amazonaws.http.conn.$Proxy30.get(Unknown Source) at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:190) at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186) at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185) at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83) at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) at com.amazonaws.http.apache.client.impl.SdkHttpClient.execute(SdkHttpClient.java:72) at com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeOneRequest(AmazonHttpClient.java:1346) at com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeHelper(AmazonHttpClient.java:1157) ... 30 more Suppressed: com.amazonaws.SdkClientException: Unable to execute HTTP request: Timeout waiting for connection from pool ... 32 more Caused by: org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.leaseConnection(PoolingHttpClientConnectionManager.java:316) at org.apache.http.impl.conn.PoolingHttpClientConnectionManager$1.get(PoolingHttpClientConnectionManager.java:282) at jdk.internal.reflect.GeneratedMethodAccessor58.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at com.amazonaws.http.conn.ClientConnectionRequestFactory$Handler.invoke(ClientConnectionRequestFactory.java:70) at com.amazonaws.http.conn.$Proxy30.get(Unknown Source) at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:190) at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186) at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185) at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83) at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) at com.amazonaws.http.apache.client.impl.SdkHttpClient.execute(SdkHttpClient.java:72) at com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeOneRequest(AmazonHttpClient.java:1346) at com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeHelper(AmazonHttpClient.java:1157) ... 30 more Suppressed: com.amazonaws.SdkClientException: Unable to execute HTTP request: Timeout waiting for connection from pool ... 32 more Caused by: org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.leaseConnection(PoolingHttpClientConnectionManager.java:316) at org.apache.http.impl.conn.PoolingHttpClientConnectionManager$1.get(PoolingHttpClientConnectionManager.java:282) at jdk.internal.reflect.GeneratedMethodAccessor58.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.M
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