Implement hidden aliases (elastic#52547)

This commit introduces hidden aliases. These are similar to hidden
indices, in that they are not visible by default, unless explicitly
specified by name or by indicating that hidden indices/aliases are
desired.

The new alias property, `is_hidden` is implemented similarly to
`is_write_index`, except that it must be consistent across all indices
with a given alias - that is, all indices with a given alias must
specify the alias as either hidden, or all specify it as non-hidden,
either explicitly or by omitting the `is_hidden` property.

docs/reference/indices/aliases.asciidoc

@@ -106,6 +106,13 @@ include::{docdir}/rest-api/common-parms.asciidoc[tag=index-alias-filter]
 +
 See <<filtered>> for an example.
 
+`is_hidden`::
+(Optional, boolean)
+If `true`, the alias will be excluded from wildcard expressions by default,
+unless overriden in the request using the `expand_wildcards` parameter,
+similar to <<index-hidden,hidden indices>>. This property must be set to the
+same value on all indices that share an alias. Defaults to `false`.
+
 `is_write_index`::
 (Optional, boolean)
 If `true`, assigns the index as an alias's write index.

server/src/main/java/org/elasticsearch/action/admin/indices/alias/Alias.java

@@ -50,6 +50,7 @@ public class Alias implements Writeable, ToXContentFragment {
     private static final ParseField INDEX_ROUTING = new ParseField("index_routing", "indexRouting", "index-routing");
     private static final ParseField SEARCH_ROUTING = new ParseField("search_routing", "searchRouting", "search-routing");
     private static final ParseField IS_WRITE_INDEX = new ParseField("is_write_index");
+    private static final ParseField IS_HIDDEN = new ParseField("is_hidden");
 
     private String name;
 
@@ -65,6 +66,9 @@ public class Alias implements Writeable, ToXContentFragment {
     @Nullable
     private Boolean writeIndex;
 
+    @Nullable
+    private Boolean isHidden;
+
     public Alias(StreamInput in) throws IOException {
         name = in.readString();
         filter = in.readOptionalString();
@@ -75,6 +79,10 @@ public Alias(StreamInput in) throws IOException {
         } else {
             writeIndex = null;
         }
+        writeIndex = in.readOptionalBoolean();
+        if (in.getVersion().onOrAfter(Version.V_7_7_0)) {
+            isHidden = in.readOptionalBoolean();
+        }
     }
 
     public Alias(String name) {
@@ -194,6 +202,21 @@ public Alias writeIndex(@Nullable Boolean writeIndex) {
         return this;
     }
 
+    /**
+     * @return whether this alias is hidden or not
+     */
+    public Boolean isHidden() {
+        return isHidden;
+    }
+
+    /**
+     * Sets whether this alias is hidden
+     */
+    public Alias isHidden(@Nullable Boolean isHidden) {
+        this.isHidden = isHidden;
+        return this;
+    }
+
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeString(name);
@@ -203,6 +226,10 @@ public void writeTo(StreamOutput out) throws IOException {
         if (out.getVersion().onOrAfter(Version.V_6_4_0)) {
             out.writeOptionalBoolean(writeIndex);
         }
+        out.writeOptionalBoolean(writeIndex);
+        if (out.getVersion().onOrAfter(Version.V_7_7_0)) {
+            out.writeOptionalBoolean(isHidden);
+        }
     }
 
     /**
@@ -235,6 +262,8 @@ public static Alias fromXContent(XContentParser parser) throws IOException {
             } else if (token == XContentParser.Token.VALUE_BOOLEAN) {
                 if (IS_WRITE_INDEX.match(currentFieldName, parser.getDeprecationHandler())) {
                     alias.writeIndex(parser.booleanValue());
+                } else if (IS_HIDDEN.match(currentFieldName, parser.getDeprecationHandler())) {
+                    alias.isHidden(parser.booleanValue());
                 }
             }
         }
@@ -264,6 +293,10 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
 
         builder.field(IS_WRITE_INDEX.getPreferredName(), writeIndex);
 
+        if (isHidden != null) {
+            builder.field(IS_HIDDEN.getPreferredName(), isHidden);
+        }
+
         builder.endObject();
         return builder;
     }

server/src/main/java/org/elasticsearch/action/admin/indices/alias/IndicesAliasesRequest.java

@@ -97,6 +97,7 @@ public static class AliasActions implements AliasesRequest, Writeable, ToXConten
         private static final ParseField INDEX_ROUTING = new ParseField("index_routing", "indexRouting", "index-routing");
         private static final ParseField SEARCH_ROUTING = new ParseField("search_routing", "searchRouting", "search-routing");
         private static final ParseField IS_WRITE_INDEX = new ParseField("is_write_index");
+        private static final ParseField IS_HIDDEN = new ParseField("is_hidden");
 
         private static final ParseField ADD = new ParseField("add");
         private static final ParseField REMOVE = new ParseField("remove");
@@ -193,6 +194,7 @@ private static ObjectParser<AliasActions, Void> parser(String name, Supplier<Ali
             ADD_PARSER.declareField(AliasActions::indexRouting, XContentParser::text, INDEX_ROUTING, ValueType.INT);
             ADD_PARSER.declareField(AliasActions::searchRouting, XContentParser::text, SEARCH_ROUTING, ValueType.INT);
             ADD_PARSER.declareField(AliasActions::writeIndex, XContentParser::booleanValue, IS_WRITE_INDEX, ValueType.BOOLEAN);
+            ADD_PARSER.declareField(AliasActions::isHidden, XContentParser::booleanValue, IS_HIDDEN, ValueType.BOOLEAN);
         }
         private static final ObjectParser<AliasActions, Void> REMOVE_PARSER = parser(REMOVE.getPreferredName(), AliasActions::remove);
         private static final ObjectParser<AliasActions, Void> REMOVE_INDEX_PARSER = parser(REMOVE_INDEX.getPreferredName(),
@@ -231,6 +233,7 @@ private static ObjectParser<AliasActions, Void> parser(String name, Supplier<Ali
         private String indexRouting;
         private String searchRouting;
         private Boolean writeIndex;
+        private Boolean isHidden;
 
         public AliasActions(AliasActions.Type type) {
             this.type = type;
@@ -250,9 +253,13 @@ public AliasActions(StreamInput in) throws IOException {
             if (in.getVersion().onOrAfter(Version.V_6_4_0)) {
                 writeIndex = in.readOptionalBoolean();
             }
+            if (in.getVersion().onOrAfter(Version.V_7_7_0)) { //TODO fix for backport of https://github.com/elastic/elasticsearch/pull/52547
+                isHidden = in.readOptionalBoolean();
+            }
             if (in.getVersion().onOrAfter(Version.V_7_0_0)) {
                 originalAliases = in.readStringArray();
             }
+
         }
 
         @Override
@@ -267,6 +274,9 @@ public void writeTo(StreamOutput out) throws IOException {
             if (out.getVersion().onOrAfter(Version.V_6_4_0)) {
                 out.writeOptionalBoolean(writeIndex);
             }
+            if (out.getVersion().onOrAfter(Version.V_7_7_0)) { //TODO fix for backport https://github.com/elastic/elasticsearch/pull/52547
+                out.writeOptionalBoolean(isHidden);
+            }
             if (out.getVersion().onOrAfter(Version.V_7_0_0)) {
                 out.writeStringArray(originalAliases);
             }
@@ -442,6 +452,18 @@ public Boolean writeIndex() {
             return writeIndex;
         }
 
+        public AliasActions isHidden(Boolean isHidden) {
+            if (type != AliasActions.Type.ADD) {
+                throw new IllegalArgumentException("[" + IS_HIDDEN.getPreferredName() + "] is unsupported for [" + type + "]");
+            }
+            this.isHidden = isHidden;
+            return this;
+        }
+
+        public Boolean isHidden() {
+            return isHidden;
+        }
+
         @Override
         public String[] aliases() {
             return aliases;
@@ -500,6 +522,9 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
             if (null != writeIndex) {
                 builder.field(IS_WRITE_INDEX.getPreferredName(), writeIndex);
             }
+            if (null != isHidden) {
+                builder.field(IS_HIDDEN.getPreferredName(), isHidden);
+            }
             builder.endObject();
             builder.endObject();
             return builder;

server/src/main/java/org/elasticsearch/action/admin/indices/alias/TransportIndicesAliasesAction.java

@@ -125,7 +125,7 @@ protected void masterOperation(final IndicesAliasesRequest request, final Cluste
                 case ADD:
                     for (String alias : concreteAliases(action, state.metaData(), index.getName())) {
                         finalActions.add(new AliasAction.Add(index.getName(), alias, action.filter(), action.indexRouting(),
-                            action.searchRouting(), action.writeIndex()));
+                            action.searchRouting(), action.writeIndex(), action.isHidden()));
                     }
                     break;
                 case REMOVE:

server/src/main/java/org/elasticsearch/action/admin/indices/rollover/TransportRolloverAction.java

@@ -214,11 +214,11 @@ static List<AliasAction> rolloverAliasToNewIndex(String oldIndex, String newInde
                                                      boolean explicitWriteIndex) {
         if (explicitWriteIndex) {
             return unmodifiableList(Arrays.asList(
-                new AliasAction.Add(newIndex, request.getAlias(), null, null, null, true),
-                new AliasAction.Add(oldIndex, request.getAlias(), null, null, null, false)));
+                new AliasAction.Add(newIndex, request.getAlias(), null, null, null, true, null),
+                new AliasAction.Add(oldIndex, request.getAlias(), null, null, null, false, null)));
         } else {
             return unmodifiableList(Arrays.asList(
-                new AliasAction.Add(newIndex, request.getAlias(), null, null, null, null),
+                new AliasAction.Add(newIndex, request.getAlias(), null, null, null, null, null),
                 new AliasAction.Remove(oldIndex, request.getAlias())));
         }
     }

server/src/main/java/org/elasticsearch/cluster/metadata/AliasAction.java

@@ -85,11 +85,13 @@ public static class Add extends AliasAction {
         @Nullable
         private final Boolean writeIndex;
 
+        @Nullable final Boolean isHidden;
+
         /**
          * Build the operation.
          */
-        public Add(String index, String alias, @Nullable String filter, @Nullable String indexRouting,
-                   @Nullable String searchRouting, @Nullable Boolean writeIndex) {
+        public Add(String index, String alias, @Nullable String filter, @Nullable String indexRouting, @Nullable String searchRouting,
+                   @Nullable Boolean writeIndex, @Nullable Boolean isHidden) {
             super(index);
             if (false == Strings.hasText(alias)) {
                 throw new IllegalArgumentException("[alias] is required");
@@ -99,6 +101,7 @@ public Add(String index, String alias, @Nullable String filter, @Nullable String
             this.indexRouting = indexRouting;
             this.searchRouting = searchRouting;
             this.writeIndex = writeIndex;
+            this.isHidden = isHidden;
         }
 
         /**
@@ -112,6 +115,11 @@ public Boolean writeIndex() {
             return writeIndex;
         }
 
+        @Nullable
+        public Boolean isHidden() {
+            return isHidden;
+        }
+
         @Override
         boolean removeIndex() {
             return false;
@@ -122,7 +130,7 @@ boolean apply(NewAliasValidator aliasValidator, MetaData.Builder metadata, Index
             aliasValidator.validate(alias, indexRouting, filter, writeIndex);
 
             AliasMetaData newAliasMd = AliasMetaData.newAliasMetaDataBuilder(alias).filter(filter).indexRouting(indexRouting)
-                    .searchRouting(searchRouting).writeIndex(writeIndex).build();
+                    .searchRouting(searchRouting).writeIndex(writeIndex).isHidden(isHidden).build();
 
             // Check if this alias already exists
             AliasMetaData currentAliasMd = index.getAliases().get(alias);

server/src/main/java/org/elasticsearch/cluster/metadata/AliasMetaData.java

@@ -41,6 +41,7 @@
 import java.io.IOException;
 import java.util.Collections;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 
 import static java.util.Collections.emptySet;
@@ -60,7 +61,11 @@ public class AliasMetaData extends AbstractDiffable<AliasMetaData> implements To
     @Nullable
     private final Boolean writeIndex;
 
-    private AliasMetaData(String alias, CompressedXContent filter, String indexRouting, String searchRouting, Boolean writeIndex) {
+    @Nullable
+    private final Boolean isHidden;
+
+    private AliasMetaData(String alias, CompressedXContent filter, String indexRouting, String searchRouting, Boolean writeIndex,
+                          @Nullable Boolean isHidden) {
         this.alias = alias;
         this.filter = filter;
         this.indexRouting = indexRouting;
@@ -71,10 +76,12 @@ private AliasMetaData(String alias, CompressedXContent filter, String indexRouti
             searchRoutingValues = emptySet();
         }
         this.writeIndex = writeIndex;
+        this.isHidden = isHidden;
     }
 
     private AliasMetaData(AliasMetaData aliasMetaData, String alias) {
-        this(alias, aliasMetaData.filter(), aliasMetaData.indexRouting(), aliasMetaData.searchRouting(), aliasMetaData.writeIndex());
+        this(alias, aliasMetaData.filter(), aliasMetaData.indexRouting(), aliasMetaData.searchRouting(), aliasMetaData.writeIndex(),
+            aliasMetaData.isHidden);
     }
 
     public String alias() {
@@ -121,6 +128,11 @@ public Boolean writeIndex() {
         return writeIndex;
     }
 
+    @Nullable
+    public Boolean isHidden() {
+        return isHidden;
+    }
+
     public static Builder builder(String alias) {
         return new Builder(alias);
     }
@@ -143,11 +155,12 @@ public boolean equals(Object o) {
 
         final AliasMetaData that = (AliasMetaData) o;
 
-        if (alias != null ? !alias.equals(that.alias) : that.alias != null) return false;
-        if (filter != null ? !filter.equals(that.filter) : that.filter != null) return false;
-        if (indexRouting != null ? !indexRouting.equals(that.indexRouting) : that.indexRouting != null) return false;
-        if (searchRouting != null ? !searchRouting.equals(that.searchRouting) : that.searchRouting != null) return false;
-        if (writeIndex != null ? writeIndex != that.writeIndex : that.writeIndex != null) return false;
+        if (Objects.equals(alias, that.alias) == false) return false;
+        if (Objects.equals(filter, that.filter) == false) return false;
+        if (Objects.equals(indexRouting, that.indexRouting) == false) return false;
+        if (Objects.equals(searchRouting, that.searchRouting) == false) return false;
+        if (Objects.equals(writeIndex, that.writeIndex) == false) return false;
+        if (Objects.equals(isHidden, that.isHidden) == false) return false;
 
         return true;
     }
@@ -187,6 +200,10 @@ public void writeTo(StreamOutput out) throws IOException {
         if (out.getVersion().onOrAfter(Version.V_6_4_0)) {
             out.writeOptionalBoolean(writeIndex());
         }
+
+        if (out.getVersion().onOrAfter(Version.V_7_7_0)) {
+            out.writeOptionalBoolean(isHidden);
+        }
     }
 
     public AliasMetaData(StreamInput in) throws IOException {
@@ -213,6 +230,12 @@ public AliasMetaData(StreamInput in) throws IOException {
         } else {
             writeIndex = null;
         }
+
+        if (in.getVersion().onOrAfter(Version.V_7_7_0)) {
+            isHidden = in.readOptionalBoolean();
+        } else {
+            isHidden = null;
+        }
     }
 
     public static Diff<AliasMetaData> readDiffFrom(StreamInput in) throws IOException {
@@ -243,6 +266,8 @@ public static class Builder {
         @Nullable
         private Boolean writeIndex;
 
+        @Nullable
+        private Boolean isHidden;
 
         public Builder(String alias) {
             this.alias = alias;
@@ -300,8 +325,13 @@ public Builder writeIndex(@Nullable Boolean writeIndex) {
             return this;
         }
 
+        public Builder isHidden(@Nullable Boolean isHidden) {
+            this.isHidden = isHidden;
+            return this;
+        }
+
         public AliasMetaData build() {
-            return new AliasMetaData(alias, filter, indexRouting, searchRouting, writeIndex);
+            return new AliasMetaData(alias, filter, indexRouting, searchRouting, writeIndex, isHidden);
         }
 
         public static void toXContent(AliasMetaData aliasMetaData, XContentBuilder builder, ToXContent.Params params) throws IOException {
@@ -327,6 +357,10 @@ public static void toXContent(AliasMetaData aliasMetaData, XContentBuilder build
                 builder.field("is_write_index", aliasMetaData.writeIndex());
             }
 
+            if (aliasMetaData.isHidden != null) {
+                builder.field("is_hidden", aliasMetaData.isHidden());
+            }
+
             builder.endObject();
         }
 
@@ -366,6 +400,8 @@ public static AliasMetaData fromXContent(XContentParser parser) throws IOExcepti
                 } else if (token == XContentParser.Token.VALUE_BOOLEAN) {
                     if ("is_write_index".equals(currentFieldName)) {
                         builder.writeIndex(parser.booleanValue());
+                    } else if ("is_hidden".equals(currentFieldName)) {
+                        builder.isHidden(parser.booleanValue());
                     }
                 }
             }