HADOOP-14467. S3Guard: Improve FNFE message when opening a stream.

Contributed by Aaron Fabbri.

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/ITestS3ADelayedFNF.java

@@ -0,0 +1,55 @@
+/*
+ * 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.hadoop.fs.s3a;
+
+import org.apache.hadoop.fs.FSDataInputStream;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.contract.ContractTestUtils;
+import org.apache.hadoop.test.LambdaTestUtils;
+import org.junit.Test;
+
+import java.io.FileNotFoundException;
+
+/**
+ * Tests behavior of a FileNotFound error that happens after open(), i.e. on
+ * the first read.
+ */
+public class ITestS3ADelayedFNF extends AbstractS3ATestBase {
+
+
+  /**
+   * See debugging documentation
+   * <a href="https://cwiki.apache.org/confluence/display/HADOOP/S3A%3A+FileNotFound+Exception+on+Read">here</a>.
+   * @throws Exception
+   */
+  @Test
+  public void testNotFoundFirstRead() throws Exception {
+    FileSystem fs = getFileSystem();
+    Path p = path("some-file");
+    ContractTestUtils.createFile(fs, p, false, new byte[] {20, 21, 22});
+
+    FSDataInputStream in = fs.open(p);
+    assertDeleted(p, false);
+
+    // This should fail since we deleted after the open.
+    LambdaTestUtils.intercept(FileNotFoundException.class, () -> in.read());
+  }
+
+}

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/S3ATestUtils.java

@@ -330,7 +330,7 @@ public final class S3ATestUtils {
   }
 
   /**
-   * Assume testing S3Guard is not enabled.
+   * Test assumption that S3Guard is/is not enabled.
    */
   public static void assumeS3GuardState(boolean shouldBeEnabled,
       Configuration originalConf) throws URISyntaxException {