[Deprecate] RepositoryData.MIN_VERSION for removal in next major rele…

…ase (#4729)

This field is only used for old snapshot generations and needs to be removed in
the next major version. This commit sets up the removal for backwards
compatibility support.

Signed-off-by: Nicholas Walter Knize <nknize@apache.org>

CHANGELOG.md

@@ -78,6 +78,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Deprecated
 
 ### Removed
+- Remove RepositoryData.MIN_VERSION support for next major release ([4729](https://github.com/opensearch-project/OpenSearch/pull/4729))
 
 ### Fixed
 - PR reference to checkout code for changelog verifier ([#4296](https://github.com/opensearch-project/OpenSearch/pull/4296))

server/src/main/java/org/opensearch/repositories/RepositoryData.java

@@ -600,9 +600,11 @@ public XContentBuilder snapshotsToXContent(final XContentBuilder builder, final
         }
         builder.endObject();
         if (shouldWriteIndexGens) {
-            builder.field(MIN_VERSION, SnapshotsService.INDEX_GEN_IN_REPO_DATA_VERSION.toString());
+            if (repoMetaVersion.before(Version.V_2_4_0)) {
+                builder.field(MIN_VERSION, SnapshotsService.INDEX_GEN_IN_REPO_DATA_VERSION.toString());
+            }
             builder.field(INDEX_METADATA_IDENTIFIERS, indexMetaDataGenerations.identifiers);
-        } else if (shouldWriteShardGens) {
+        } else if (shouldWriteShardGens && repoMetaVersion.before(Version.V_2_4_0)) {
             // Add min version field to make it impossible for older OpenSearch versions to deserialize this object
             builder.field(MIN_VERSION, SnapshotsService.SHARD_GEN_IN_REPO_DATA_VERSION.toString());
         }
@@ -645,10 +647,14 @@ public static RepositoryData snapshotsFromXContent(XContentParser parser, long g
                     XContentParserUtils.ensureExpectedToken(XContentParser.Token.START_OBJECT, parser.nextToken(), parser);
                     indexMetaIdentifiers = parser.mapStrings();
                     break;
-                case MIN_VERSION:
-                    XContentParserUtils.ensureExpectedToken(XContentParser.Token.VALUE_STRING, parser.nextToken(), parser);
-                    final Version version = Version.fromString(parser.text());
-                    assert SnapshotsService.useShardGenerations(version);
+                case MIN_VERSION: // todo: remove in 3.0
+                    if (Version.CURRENT.major < 3) {
+                        XContentParserUtils.ensureExpectedToken(XContentParser.Token.VALUE_STRING, parser.nextToken(), parser);
+                        final Version version = Version.fromString(parser.text());
+                        assert SnapshotsService.useShardGenerations(version);
+                    } else {
+                        throw new OpenSearchParseException("Field [{}] was removed in version 2.4.0 and no longer supported.", MIN_VERSION);
+                    }
                     break;
                 default:
                     XContentParserUtils.throwUnknownField(field, parser.getTokenLocation());