support opensearch 2.x

Author: unautre

janusgraph-es/src/main/java/org/janusgraph/diskstorage/es/ElasticMajorVersion.java

@@ -14,6 +14,7 @@
 
 package org.janusgraph.diskstorage.es;
 
+import java.util.Map;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -39,7 +40,14 @@ public int getValue() {
         return value;
     }
 
-    public static ElasticMajorVersion parse(final String value) {
+    public static ElasticMajorVersion parse(Map<String, Object> version) {
+        // opensearch is mostly compatible with ElasticSearch 7.10
+        if (version != null && "opensearch".equals(version.get("distribution")))
+            return ElasticMajorVersion.SEVEN;
+        return parse(version != null ? (String) version.get("number") : null);
+    }
+    
+    static ElasticMajorVersion parse(final String value) {
         final Matcher m = value != null ? PATTERN.matcher(value) : null;
         switch (m != null && m.find() ? Integer.parseInt(m.group(1)) : -1) {
             case 6:

janusgraph-es/src/main/java/org/janusgraph/diskstorage/es/rest/RestElasticSearchClient.java

@@ -166,9 +166,9 @@ public ElasticMajorVersion getMajorVersion() {
             final Response response = delegate.performRequest(INFO_REQUEST);
             try (final InputStream inputStream = response.getEntity().getContent()) {
                 final ClusterInfo info = mapper.readValue(inputStream, ClusterInfo.class);
-                majorVersion = ElasticMajorVersion.parse(info.getVersion() != null ? (String) info.getVersion().get("number") : null);
+                majorVersion = ElasticMajorVersion.parse(info.getVersion());
             }
-        } catch (final IOException e) {
+        } catch (final IOException|IllegalArgumentException e) {
             log.warn("Unable to determine Elasticsearch server version. Default to {}.", majorVersion, e);
         }
 
@@ -751,7 +751,7 @@ private Response performRequest(Request request, byte[] requestData) throws IOEx
     }
 
     @JsonIgnoreProperties(ignoreUnknown=true)
-    private static final class ClusterInfo {
+    public static final class ClusterInfo {
 
         private Map<String,Object> version;