[LIVY-658] RSCDriver should catch exception if cancel job failed duri…

…ng shutdown

## What changes were proposed in this pull request?

Currently, if startup meet exception, exception will trigger spark to shutdown, then trigger cancel job, but cancel job will throw another exception due to spark is not initialized. The new exception will swallow the old exception.

https://issues.apache.org/jira/browse/LIVY-658

Before changes:
![cancel job exception](https://user-images.githubusercontent.com/7855100/64118287-f0961900-cdc9-11e9-9b72-d051fb4bdbdf.jpg)

After changes:
![cancel job exception after fix](https://user-images.githubusercontent.com/7855100/64118295-f4c23680-cdc9-11e9-9a2d-38efa0770a99.jpg)

## How was this patch tested?

Tested manually， and  add unit test.

Please review https://livy.incubator.apache.org/community/ before opening a pull request.

Author: Jeffrey(Xilang) Yan <[email protected]>

Closes apache#223 from yantzu/initialize_exception_swallow_by_shutdown_exception.

rsc/src/main/java/org/apache/livy/rsc/driver/RSCDriver.java

@@ -124,7 +124,11 @@ private synchronized void shutdown() {
 
     // Cancel any pending jobs.
     for (JobWrapper<?> job : activeJobs.values()) {
-      job.cancel();
+      try {
+        job.cancel();
+      } catch (Exception e) {
+        LOG.warn("Error during cancel job.", e);
+      }
     }
 
     try {

rsc/src/test/java/org/apache/livy/rsc/driver/TestRSCDriver.java

@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.livy.rsc.driver;
+
+import org.apache.spark.SparkConf;
+import org.junit.Test;
+
+import org.apache.livy.rsc.BaseProtocol;
+import org.apache.livy.rsc.RSCConf;
+
+public class TestRSCDriver {
+  @Test(expected = IllegalArgumentException.class)
+  public void testCancelJobAfterInitializeFailed()
+      throws Exception {
+    //use empty Conf to trigger initialize throw IllegalArgumentException
+    RSCDriver rscDriver = new RSCDriver(new SparkConf(), new RSCConf());
+    //add asynchronous dummy job request to trigger cancel job failure
+    rscDriver.handle(null, new BaseProtocol.BypassJobRequest("RequestId", null, null, false));
+    rscDriver.run();
+  }
+}