[elasticsearch] require path.home in embedded mode

Today when running the Elasticsearch binding in embedded mode, a
temporary directory is used. This can be confusing for running usual
load-then-run style workflows because the temporary directory will not
be the same between runs. Instead, we should just require a directory
when running in embedded mode and this commit makes this the case.

elasticsearch/src/main/java/com/yahoo/ycsb/db/ElasticsearchClient.java

@@ -82,20 +82,29 @@ public class ElasticsearchClient extends DB {
    */
   @Override
   public void init() throws DBException {
-    Properties props = getProperties();
+    final Properties props = getProperties();
+
+    // Check if transport client needs to be used (To connect to multiple
+    // elasticsearch nodes)
+    remoteMode = Boolean.parseBoolean(props.getProperty("es.remote", "false"));
+
+    final String pathHome = props.getProperty("path.home");
+
+    // when running in embedded mode, require path.home
+    if (!remoteMode && (pathHome == null || pathHome.isEmpty())) {
+      throw new IllegalArgumentException("path.home must be specified when running in embedded mode");
+    }
+
     this.indexKey = props.getProperty("es.index.key", DEFAULT_INDEX_KEY);
 
     int numberOfShards = parseIntegerProperty(props, "es.number_of_shards", NUMBER_OF_SHARDS);
     int numberOfReplicas = parseIntegerProperty(props, "es.number_of_replicas", NUMBER_OF_REPLICAS);
 
-    // Check if transport client needs to be used (To connect to multiple
-    // elasticsearch nodes)
-    remoteMode = Boolean.parseBoolean(props.getProperty("es.remote", "false"));
     Boolean newdb = Boolean.parseBoolean(props.getProperty("es.newdb", "false"));
     Builder settings = Settings.settingsBuilder()
         .put("cluster.name", DEFAULT_CLUSTER_NAME)
         .put("node.local", Boolean.toString(!remoteMode))
-        .put("path.home", System.getProperty("java.io.tmpdir"));
+        .put("path.home", pathHome);
 
     // if properties file contains elasticsearch user defined properties
     // add it to the settings file (will overwrite the defaults).

elasticsearch/src/test/java/com/yahoo/ycsb/db/ElasticsearchClientTest.java

@@ -29,9 +29,13 @@ import org.junit.After;
 import org.junit.AfterClass;
 import org.junit.Before;
 import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
 
 import java.util.HashMap;
+import java.util.Properties;
 import java.util.Set;
 import java.util.Vector;
 
@@ -39,6 +43,7 @@ import static org.junit.Assert.assertEquals;
 
 public class ElasticsearchClientTest {
 
+    @ClassRule public final static TemporaryFolder temp = new TemporaryFolder();
     protected final static ElasticsearchClient instance = new ElasticsearchClient();
     protected final static HashMap<String, ByteIterator> MOCK_DATA;
     protected final static String MOCK_TABLE = "MOCK_TABLE";
@@ -55,6 +60,9 @@ public class ElasticsearchClientTest {
 
     @BeforeClass
     public static void setUpClass() throws DBException {
+        final Properties props = new Properties();
+        props.put("path.home", temp.getRoot().toString());
+        instance.setProperties(props);
         instance.init();
     }