Add new flag to check whether alias exists on remove (#58100)

This allows doing true CAS operations on aliases, making sure that an alias is actually properly
moved from a given source index onto a given target index. This is useful to ensure that an
alias is actually moved from a given index to another one, and not just added to another index.

docs/reference/indices/aliases.asciidoc

@@ -113,6 +113,10 @@ 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`.
 
+`must_exist`::
+(Optional, boolean)
+If `true`, the alias to remove must exist. 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/IndicesAliasesRequest.java

@@ -98,6 +98,7 @@ public static class AliasActions implements AliasesRequest, Writeable, ToXConten
  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 MUST_EXIST = new ParseField("must_exist");
 
  private static final ParseField ADD = new ParseField("add");
  private static final ParseField REMOVE = new ParseField("remove");
@@ -195,6 +196,7 @@ private static ObjectParser<AliasActions, Void> parser(String name, Supplier<Ali
  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);
+ ADD_PARSER.declareField(AliasActions::mustExist, XContentParser::booleanValue, MUST_EXIST, 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(),
@@ -234,6 +236,7 @@ private static ObjectParser<AliasActions, Void> parser(String name, Supplier<Ali
  private String searchRouting;
  private Boolean writeIndex;
  private Boolean isHidden;
+ private Boolean mustExist;
 
  public AliasActions(AliasActions.Type type) {
  this.type = type;
@@ -259,7 +262,11 @@ public AliasActions(StreamInput in) throws IOException {
  if (in.getVersion().onOrAfter(Version.V_7_0_0)) {
  originalAliases = in.readStringArray();
  }
-
+ if (in.getVersion().onOrAfter(Version.V_7_9_0)) {
+ mustExist = in.readOptionalBoolean();
+ } else {
+ mustExist = null;
+ }
  }
 
  @Override
@@ -280,6 +287,9 @@ public void writeTo(StreamOutput out) throws IOException {
  if (out.getVersion().onOrAfter(Version.V_7_0_0)) {
  out.writeStringArray(originalAliases);
  }
+ if (out.getVersion().onOrAfter(Version.V_7_9_0)) {
+ out.writeOptionalBoolean(mustExist);
+ }
  }
 
  /**
@@ -464,6 +474,18 @@ public Boolean isHidden() {
  return isHidden;
  }
 
+ public AliasActions mustExist(Boolean mustExist) {
+ if (type != Type.REMOVE) {
+ throw new IllegalArgumentException("[" + MUST_EXIST.getPreferredName() + "] is unsupported for [" + type + "]");
+ }
+ this.mustExist = mustExist;
+ return this;
+ }
+
+ public Boolean mustExist() {
+ return mustExist;
+ }
+
  @Override
  public String[] aliases() {
  return aliases;

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

@@ -130,7 +130,7 @@ protected void masterOperation(final IndicesAliasesRequest request, final Cluste
  break;
  case REMOVE:
  for (String alias : concreteAliases(action, state.metadata(), index.getName())) {
- finalActions.add(new AliasAction.Remove(index.getName(), alias));
+ finalActions.add(new AliasAction.Remove(index.getName(), alias, action.mustExist()));
  }
  break;
  case REMOVE_INDEX:

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

@@ -229,7 +229,7 @@ static List<AliasAction> rolloverAliasToNewIndex(String oldIndex, String newInde
  } else {
  return Collections.unmodifiableList(Arrays.asList(
  new AliasAction.Add(newIndex, alias, null, null, null, null, isHidden),
- new AliasAction.Remove(oldIndex, alias)));
+ new AliasAction.Remove(oldIndex, alias, null)));
  }
  }
 

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

@@ -149,16 +149,19 @@ boolean apply(NewAliasValidator aliasValidator, Metadata.Builder metadata, Index
  */
  public static class Remove extends AliasAction {
  private final String alias;
+ @Nullable
+ private final Boolean mustExist;
 
  /**
  * Build the operation.
  */
- public Remove(String index, String alias) {
+ public Remove(String index, String alias, @Nullable Boolean mustExist) {
  super(index);
  if (false == Strings.hasText(alias)) {
  throw new IllegalArgumentException("[alias] is required");
  }
  this.alias = alias;
+ this.mustExist = mustExist;
  }
 
  /**
@@ -176,6 +179,9 @@ boolean removeIndex() {
  @Override
  boolean apply(NewAliasValidator aliasValidator, Metadata.Builder metadata, IndexMetadata index) {
  if (false == index.getAliases().containsKey(alias)) {
+ if (mustExist != null && mustExist.booleanValue()) {
+ throw new IllegalArgumentException("required alias [" + alias + "] does not exist");
+ }
  return false;
  }
  metadata.put(IndexMetadata.builder(index).removeAlias(alias));

server/src/test/java/org/elasticsearch/action/admin/indices/alias/AliasActionsTests.java

@@ -108,6 +108,17 @@ public void testBadOptionsInNonIndex() {
  assertEquals("[filter] is unsupported for [" + action.actionType() + "]", e.getMessage());
  }
 
+ public void testMustExistOption() {
+ final boolean mustExist = randomBoolean();
+ AliasActions removeAliasAction = AliasActions.remove();
+ assertNull(removeAliasAction.mustExist());
+ removeAliasAction.mustExist(mustExist);
+ assertEquals(mustExist, removeAliasAction.mustExist());
+ AliasActions action = randomBoolean() ? AliasActions.add() : AliasActions.removeIndex();
+ Exception e = expectThrows(IllegalArgumentException.class, () -> action.mustExist(mustExist));
+ assertEquals("[must_exist] is unsupported for [" + action.actionType() + "]", e.getMessage());
+ }
+
  public void testParseAdd() throws IOException {
  String[] indices = generateRandomStringArray(10, 5, false, false);
  String[] aliases = generateRandomStringArray(10, 5, false, false);

server/src/test/java/org/elasticsearch/cluster/metadata/MetadataIndexAliasesServiceTests.java

@@ -85,7 +85,7 @@ public void testAddAndRemove() {
  // Remove the alias from it while adding another one
  before = after;
  after = service.applyAliasActions(before, Arrays.asList(
- new AliasAction.Remove(index, "test"),
+ new AliasAction.Remove(index, "test", null),
  new AliasAction.Add(index, "test_2", null, null, null, null, null)));
  assertNull(after.metadata().getIndicesLookup().get("test"));
  alias = after.metadata().getIndicesLookup().get("test_2");
@@ -96,12 +96,52 @@ public void testAddAndRemove() {
 
  // Now just remove on its own
  before = after;
- after = service.applyAliasActions(before, singletonList(new AliasAction.Remove(index, "test_2")));
+ after = service.applyAliasActions(before, singletonList(new AliasAction.Remove(index, "test_2", randomBoolean())));
  assertNull(after.metadata().getIndicesLookup().get("test"));
  assertNull(after.metadata().getIndicesLookup().get("test_2"));
  assertAliasesVersionIncreased(index, before, after);
  }
 
+ public void testMustExist() {
+ // Create a state with a single index
+ String index = randomAlphaOfLength(5);
+ ClusterState before = createIndex(ClusterState.builder(ClusterName.DEFAULT).build(), index);
+
+ // Add an alias to it
+ ClusterState after = service.applyAliasActions(before, singletonList(new AliasAction.Add(index, "test", null, null, null, null,
+ null)));
+ IndexAbstraction alias = after.metadata().getIndicesLookup().get("test");
+ assertNotNull(alias);
+ assertThat(alias.getType(), equalTo(IndexAbstraction.Type.ALIAS));
+ assertThat(alias.getIndices(), contains(after.metadata().index(index)));
+ assertAliasesVersionIncreased(index, before, after);
+
+ // Remove the alias from it with mustExist == true while adding another one
+ before = after;
+ after = service.applyAliasActions(before, Arrays.asList(
+ new AliasAction.Remove(index, "test", true),
+ new AliasAction.Add(index, "test_2", null, null, null, null, null)));
+ assertNull(after.metadata().getIndicesLookup().get("test"));
+ alias = after.metadata().getIndicesLookup().get("test_2");
+ assertNotNull(alias);
+ assertThat(alias.getType(), equalTo(IndexAbstraction.Type.ALIAS));
+ assertThat(alias.getIndices(), contains(after.metadata().index(index)));
+ assertAliasesVersionIncreased(index, before, after);
+
+ // Now just remove on its own
+ before = after;
+ after = service.applyAliasActions(before, singletonList(new AliasAction.Remove(index, "test_2", randomBoolean())));
+ assertNull(after.metadata().getIndicesLookup().get("test"));
+ assertNull(after.metadata().getIndicesLookup().get("test_2"));
+ assertAliasesVersionIncreased(index, before, after);
+
+ // Show that removing non-existing alias with mustExist == true fails
+ final ClusterState finalCS = after;
+ final IllegalArgumentException iae = expectThrows(IllegalArgumentException.class,
+ () -> service.applyAliasActions(finalCS, singletonList(new AliasAction.Remove(index, "test_2", true))));
+ assertThat(iae.getMessage(), containsString("required alias [test_2] does not exist"));
+ }
+
  public void testMultipleIndices() {
  final int length = randomIntBetween(2, 8);
  final Set<String> indices = new HashSet<>(length);
@@ -184,7 +224,7 @@ public void testAliasesVersionUnchangedWhenActionsAreIdempotent() {
  // now perform a remove and add for each alias which is idempotent, the resulting aliases are unchanged
  final List<AliasAction> removeAndAddActions = new ArrayList<>(2 * length);
  for (final String aliasName : aliasNames) {
- removeAndAddActions.add(new AliasAction.Remove(index, aliasName));
+ removeAndAddActions.add(new AliasAction.Remove(index, aliasName, null));
  removeAndAddActions.add(new AliasAction.Add(index, aliasName, null, null, null, null, null));
  }
  final ClusterState afterRemoveAndAddAlias = service.applyAliasActions(afterAddingAlias, removeAndAddActions);