[FLINK-30371] Fixed a Problem in the Exception Handling of the Close Method.

This Problem leads to Connection Leaks if some problem occurs.

Author: KevDi

flink-connector-jdbc/src/main/java/org/apache/flink/connector/jdbc/internal/JdbcOutputFormat.java

@@ -262,7 +262,7 @@ public synchronized void close() {
                     flush();
                 } catch (Exception e) {
                     LOG.warn("Writing records to JDBC failed.", e);
-                    throw new RuntimeException("Writing records to JDBC failed.", e);
+                    flushException = e;
                 }
             }
 

flink-connector-jdbc/src/test/java/org/apache/flink/connector/jdbc/JdbcTestFixture.java

@@ -44,6 +44,7 @@ public class JdbcTestFixture implements DerbyTestBase {
     public static final String OUTPUT_TABLE = "newbooks";
     public static final String OUTPUT_TABLE_2 = "newbooks2";
     public static final String OUTPUT_TABLE_3 = "newbooks3";
+    public static final String OUTPUT_TABLE_4 = "newbooks4";
     public static final String WORDS_TABLE = "words";
     public static final String SELECT_ALL_BOOKS = "select * from " + INPUT_TABLE;
     public static final String SELECT_ID_BOOKS = "select id from " + INPUT_TABLE;
@@ -189,6 +190,7 @@ public static void initSchema(DatabaseMetadata metadata) throws SQLException {
             createTable(conn, OUTPUT_TABLE);
             createTable(conn, OUTPUT_TABLE_2);
             createTable(conn, OUTPUT_TABLE_3);
+            createTable(conn, OUTPUT_TABLE_4);
             createWordsTable(conn);
         }
     }
@@ -232,6 +234,7 @@ public static void cleanUpDatabasesStatic(DatabaseMetadata dbMetadata) throws SQ
             stat.executeUpdate("DROP TABLE " + OUTPUT_TABLE);
             stat.executeUpdate("DROP TABLE " + OUTPUT_TABLE_2);
             stat.executeUpdate("DROP TABLE " + OUTPUT_TABLE_3);
+            stat.executeUpdate("DROP TABLE " + OUTPUT_TABLE_4);
             stat.executeUpdate("DROP TABLE " + WORDS_TABLE);
         }
     }

flink-connector-jdbc/src/test/java/org/apache/flink/connector/jdbc/internal/JdbcTableOutputFormatTest.java

@@ -23,6 +23,7 @@
 import org.apache.flink.api.java.tuple.Tuple2;
 import org.apache.flink.connector.jdbc.JdbcDataTestBase;
 import org.apache.flink.connector.jdbc.JdbcExecutionOptions;
+import org.apache.flink.connector.jdbc.JdbcRowOutputFormat;
 import org.apache.flink.connector.jdbc.internal.connection.SimpleJdbcConnectionProvider;
 import org.apache.flink.connector.jdbc.internal.executor.JdbcBatchStatementExecutor;
 import org.apache.flink.connector.jdbc.internal.options.InternalJdbcConnectionOptions;
@@ -34,6 +35,7 @@
 import org.junit.jupiter.api.Test;
 import org.mockito.Mockito;
 
+import java.io.IOException;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.PreparedStatement;
@@ -44,9 +46,7 @@
 import java.util.Arrays;
 import java.util.List;
 
-import static org.apache.flink.connector.jdbc.JdbcTestFixture.OUTPUT_TABLE;
-import static org.apache.flink.connector.jdbc.JdbcTestFixture.TEST_DATA;
-import static org.apache.flink.connector.jdbc.JdbcTestFixture.TestEntry;
+import static org.apache.flink.connector.jdbc.JdbcTestFixture.*;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.doReturn;
 
@@ -221,6 +221,30 @@ void testJdbcOutputFormat() throws Exception {
         check(expected);
     }
 
+    @Test
+    public void testExceptionOnFlush() {
+        JdbcRowOutputFormat jdbcOutputFormat =
+                JdbcRowOutputFormat.buildJdbcOutputFormat()
+                        .setDrivername(getMetadata().getDriverClass())
+                        .setDBUrl(getMetadata().getJdbcUrl())
+                        .setQuery(String.format(INSERT_TEMPLATE, OUTPUT_TABLE_4))
+                        .setBatchSize(2)
+                        .finish();
+        setRuntimeContext(jdbcOutputFormat, true);
+        try {
+            jdbcOutputFormat.open(0, 1);
+
+            jdbcOutputFormat.writeRecord(toRow(TEST_DATA[1]));
+            jdbcOutputFormat.writeRecord(toRow(TEST_DATA[1]));
+        } catch (IOException e) {
+            try {
+                jdbcOutputFormat.close();
+            } catch (Exception e1) {
+                assertThat(jdbcOutputFormat.getConnection()).isEqualTo(null);
+            }
+        }
+    }
+
     private void check(Row[] rows) throws SQLException {
         check(rows, getMetadata().getJdbcUrl(), OUTPUT_TABLE, fieldNames);
     }