GH-139: [Flight] Stop return null from MetadataAdapter.getAll(String) and getAllByte(String)

Author: axreldable

flight/flight-core/src/main/java/org/apache/arrow/flight/CallHeaders.java

@@ -26,10 +26,20 @@ public interface CallHeaders {
   /** Get the value of a metadata key. If multiple values are present, then get the last one. */
   byte[] getByte(String key);
 
-  /** Get all values present for the given metadata key. */
+  /**
+   * Get all values present for the given metadata key.
+   *
+   * @param key the metadata key
+   * @return an iterable of all values for the key. Returns an empty iterable if no value to return.
+   */
   Iterable<String> getAll(String key);
 
-  /** Get all values present for the given metadata key. */
+  /**
+   * Get all values present for the given metadata key.
+   *
+   * @param key the metadata key
+   * @return an iterable of all values for the key. Returns an empty iterable if no value to return.
+   */
   Iterable<byte[]> getAllByte(String key);
 
   /**

flight/flight-core/src/main/java/org/apache/arrow/flight/ServerSessionMiddleware.java

@@ -80,20 +80,18 @@ public ServerSessionMiddleware onCallStarted(
       String sessionId = null;
 
       final Iterable<String> it = incomingHeaders.getAll("cookie");
-      if (it != null) {
-        findIdCookie:
-        for (final String headerValue : it) {
-          for (final String cookie : headerValue.split(" ;")) {
-            final String[] cookiePair = cookie.split("=");
-            if (cookiePair.length != 2) {
-              // Soft failure:  Ignore invalid cookie list field
-              break;
-            }
-
-            if (sessionCookieName.equals(cookiePair[0]) && cookiePair[1].length() > 0) {
-              sessionId = cookiePair[1];
-              break findIdCookie;
-            }
+      findIdCookie:
+      for (final String headerValue : it) {
+        for (final String cookie : headerValue.split(" ;")) {
+          final String[] cookiePair = cookie.split("=");
+          if (cookiePair.length != 2) {
+            // Soft failure:  Ignore invalid cookie list field
+            break;
+          }
+
+          if (sessionCookieName.equals(cookiePair[0]) && cookiePair[1].length() > 0) {
+            sessionId = cookiePair[1];
+            break findIdCookie;
           }
         }
       }

flight/flight-core/src/main/java/org/apache/arrow/flight/client/ClientCookieMiddleware.java

@@ -100,10 +100,7 @@ public void onBeforeSendingHeaders(CallHeaders outgoingHeaders) {
 
   @Override
   public void onHeadersReceived(CallHeaders incomingHeaders) {
-    final Iterable<String> setCookieHeaders = incomingHeaders.getAll(SET_COOKIE_HEADER);
-    if (setCookieHeaders != null) {
-      factory.updateCookies(setCookieHeaders);
-    }
+    factory.updateCookies(incomingHeaders.getAll(SET_COOKIE_HEADER));
   }
 
   @Override

flight/flight-core/src/main/java/org/apache/arrow/flight/grpc/MetadataAdapter.java

@@ -18,6 +18,7 @@
 
 import io.grpc.Metadata;
 import java.nio.charset.StandardCharsets;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.stream.Collectors;
@@ -53,13 +54,15 @@ public byte[] getByte(String key) {
 
   @Override
   public Iterable<String> getAll(String key) {
-    return this.metadata.getAll(Metadata.Key.of(key, Metadata.ASCII_STRING_MARSHALLER));
+    final Iterable<String> all = this.metadata.getAll(Metadata.Key.of(key, Metadata.ASCII_STRING_MARSHALLER));
+    return all != null ? all : Collections.emptyList();
   }
 
   @Override
   public Iterable<byte[]> getAllByte(String key) {
     if (key.endsWith(Metadata.BINARY_HEADER_SUFFIX)) {
-      return this.metadata.getAll(Metadata.Key.of(key, Metadata.BINARY_BYTE_MARSHALLER));
+      final Iterable<byte[]> all = this.metadata.getAll(Metadata.Key.of(key, Metadata.BINARY_BYTE_MARSHALLER));
+      return all != null ? all : Collections.emptyList();
     }
     return StreamSupport.stream(getAll(key).spliterator(), false)
         .map(String::getBytes)

flight/flight-core/src/test/java/org/apache/arrow/flight/TestCallOptions.java

@@ -21,6 +21,7 @@
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
 
@@ -110,6 +111,16 @@ public void mixedProperties() {
     testHeaders(headers);
   }
 
+  @Test
+  public void getAllReturnsEmptyIterableForMissingKey() {
+    FlightCallHeaders headers = new FlightCallHeaders();
+
+    assertNotNull(headers.getAll("missing"));
+    assertFalse(headers.getAll("missing").iterator().hasNext());
+    assertNotNull(headers.getAllByte("missing-bin"));
+    assertFalse(headers.getAllByte("missing-bin").iterator().hasNext());
+  }
+
   private void testHeaders(CallHeaders headers) {
     try (BufferAllocator a = new RootAllocator(Long.MAX_VALUE);
         HeaderProducer producer = new HeaderProducer();

flight/flight-core/src/test/java/org/apache/arrow/flight/TestErrorMetadata.java

@@ -20,6 +20,7 @@
 import static org.apache.arrow.flight.Location.forGrpcInsecure;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
@@ -119,6 +120,16 @@ public void testFlightMetadata() throws Exception {
     }
   }
 
+  @Test
+  public void getAllReturnsEmptyIterableForMissingKey() {
+    ErrorFlightMetadata metadata = new ErrorFlightMetadata();
+
+    assertNotNull(metadata.getAll("missing"));
+    assertFalse(metadata.getAll("missing").iterator().hasNext());
+    assertNotNull(metadata.getAllByte("missing-bin"));
+    assertFalse(metadata.getAllByte("missing-bin").iterator().hasNext());
+  }
+
   private static class StatusRuntimeExceptionProducer extends NoOpFlightProducer {
     private final PerfOuterClass.Perf perf;
 

flight/flight-core/src/test/java/org/apache/arrow/flight/grpc/TestMetadataAdapter.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.arrow.flight.grpc;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import io.grpc.Metadata;
+import org.junit.jupiter.api.Test;
+
+public class TestMetadataAdapter {
+
+  @Test
+  public void getAllReturnsEmptyIterableForMissingKey() {
+    MetadataAdapter headers = new MetadataAdapter(new Metadata());
+
+    assertNotNull(headers.getAll("missing"));
+    assertFalse(headers.getAll("missing").iterator().hasNext());
+    assertNotNull(headers.getAllByte("missing-bin"));
+    assertFalse(headers.getAllByte("missing-bin").iterator().hasNext());
+  }
+}