[FLINK-9765] [sql-client] Improve CLI responsiveness when cluster is …

…not reachable

Moves the job cancellation into the final phase of the refresh thread in order to
keep the CLI responsive.

This closes apache#6265.

flink-libraries/flink-sql-client/src/main/java/org/apache/flink/table/client/cli/CliResultView.java

@@ -217,15 +217,7 @@ protected List<AttributedString> computeMainLines() {
 
 	@Override
 	protected void cleanUp() {
-		// stop retrieval
 		stopRetrieval();
-
-		// cancel table program
-		try {
-			client.getExecutor().cancelQuery(client.getContext(), resultDescriptor.getResultId());
-		} catch (SqlExecutionException e) {
-			// ignore further exceptions
-		}
 	}
 
 	// --------------------------------------------------------------------------------------------
@@ -285,6 +277,15 @@ public void run() {
 					display();
 				}
 			}
+
+			// cancel table program
+			try {
+				// the cancellation happens in the refresh thread in order to keep the main thread
+				// responsive at all times; esp. if the cluster is not available
+				client.getExecutor().cancelQuery(client.getContext(), resultDescriptor.getResultId());
+			} catch (SqlExecutionException e) {
+				// ignore further exceptions
+			}
 		}
 	}
 }

flink-libraries/flink-sql-client/src/main/java/org/apache/flink/table/client/gateway/Executor.java

@@ -83,7 +83,8 @@ public interface Executor {
 	List<Row> retrieveResultPage(String resultId, int page) throws SqlExecutionException;
 
 	/**
-	 * Cancels a table program and stops the result retrieval.
+	 * Cancels a table program and stops the result retrieval. Blocking until cancellation command has
+	 * been sent to cluster.
 	 */
 	void cancelQuery(SessionContext session, String resultId) throws SqlExecutionException;