Added HadoopUtils for building the proper core-site.xml configured Ha…

…doopConfiguration.

src/main/java/org/apache/iceberg/rest/HadoopUtils.java

@@ -0,0 +1,91 @@
+/*
+ * 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.iceberg.rest;
+
+import java.io.File;
+
+import org.apache.hadoop.conf.Configuration;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Utility class to work with Apache Hadoop MapRed classes.
+ */
+public final class HadoopUtils {
+    private static final Logger LOG = LoggerFactory.getLogger(RESTCatalogServer.class);
+
+    /**
+     * Returns a new Hadoop Configuration object using the path to the hadoop conf configured
+     * in the main configuration (flink-conf.yaml).
+     * This method is public because its being used in the HadoopDataSource.
+     */
+    public static org.apache.hadoop.conf.Configuration getCoreSiteConfiguration() {
+        Configuration retConf = new org.apache.hadoop.conf.Configuration();
+
+        // We need to load both core-site.xml to determine the default fs path
+        // Approach environment variables
+        if (LOG.isDebugEnabled()) {
+            LOG.debug(
+                    "Building possible paths to core-site.xml for hadoop configuration");
+        }
+        String[] possibleHadoopConfPaths = new String[3];
+        possibleHadoopConfPaths[0] = System.getenv("HADOOP_CONF_DIR");
+
+        if (System.getenv("HADOOP_HOME") != null) {
+            possibleHadoopConfPaths[1] = System.getenv("HADOOP_HOME") + "/conf";
+            possibleHadoopConfPaths[2] = System.getenv("HADOOP_HOME") + "/etc/hadoop"; // hadoop 2.2
+        }
+
+        for (String possibleHadoopConfPath : possibleHadoopConfPaths) {
+            if (possibleHadoopConfPath != null) {
+                if (LOG.isDebugEnabled()) {
+                    LOG.debug(
+                            "Found possibleHadoopConfPath entry: " + possibleHadoopConfPath);
+                }
+                if (new File(possibleHadoopConfPath).exists()) {
+                    if (LOG.isDebugEnabled()) {
+                        LOG.debug(
+                                "possibleHadoopConfPath entry (" + possibleHadoopConfPath + ") exists.");
+                    }
+                    if (new File(possibleHadoopConfPath + "/core-site.xml").exists()) {
+                        if (LOG.isDebugEnabled()) {
+                            LOG.debug(
+                                    "Core Site config (" + possibleHadoopConfPath + "/core-site.xml) exists.");
+                        }
+                        retConf.addResource(
+                                new org.apache.hadoop.fs.Path(possibleHadoopConfPath + "/core-site.xml"));
+
+                        if (LOG.isDebugEnabled()) {
+                            LOG.debug(
+                                    "Adding " + possibleHadoopConfPath + "/core-site.xml to hadoop configuration");
+                        }
+                    }
+                }
+            }
+        }
+        return retConf;
+    }
+
+    /**
+     * Private constructor to prevent instantiation.
+     */
+    private HadoopUtils() {
+        throw new RuntimeException();
+    }
+}