Add a deprecation notice to shadow replicas (#22647)

Relates to #22024

On top of documentation, the PR adds deprecation loggers and deals with the resulting warning headers.

The yaml test is set exclude versions up to 6.0. This is need to make sure bwc tests pass until this is backported to 5.2.0 . Once that's done, I will change the yaml test version limits

core/src/main/java/org/elasticsearch/cluster/metadata/IndexMetaData.java

@@ -190,11 +190,11 @@ static Setting<Integer> buildNumberOfShardsSetting() {
         Setting.intSetting(SETTING_NUMBER_OF_REPLICAS, 1, 0, Property.Dynamic, Property.IndexScope);
     public static final String SETTING_SHADOW_REPLICAS = "index.shadow_replicas";
     public static final Setting<Boolean> INDEX_SHADOW_REPLICAS_SETTING =
-        Setting.boolSetting(SETTING_SHADOW_REPLICAS, false, Property.IndexScope);
+        Setting.boolSetting(SETTING_SHADOW_REPLICAS, false, Property.IndexScope, Property.Deprecated);
 
     public static final String SETTING_SHARED_FILESYSTEM = "index.shared_filesystem";
     public static final Setting<Boolean> INDEX_SHARED_FILESYSTEM_SETTING =
-        Setting.boolSetting(SETTING_SHARED_FILESYSTEM, false, Property.IndexScope);
+        Setting.boolSetting(SETTING_SHARED_FILESYSTEM, INDEX_SHADOW_REPLICAS_SETTING, Property.IndexScope, Property.Deprecated);
 
     public static final String SETTING_AUTO_EXPAND_REPLICAS = "index.auto_expand_replicas";
     public static final Setting<AutoExpandReplicas> INDEX_AUTO_EXPAND_REPLICAS_SETTING = AutoExpandReplicas.SETTING;
@@ -235,7 +235,8 @@ static Setting<Integer> buildNumberOfShardsSetting() {
         new Setting<>(SETTING_DATA_PATH, "", Function.identity(), Property.IndexScope);
     public static final String SETTING_SHARED_FS_ALLOW_RECOVERY_ON_ANY_NODE = "index.shared_filesystem.recover_on_any_node";
     public static final Setting<Boolean> INDEX_SHARED_FS_ALLOW_RECOVERY_ON_ANY_NODE_SETTING =
-        Setting.boolSetting(SETTING_SHARED_FS_ALLOW_RECOVERY_ON_ANY_NODE, false, Property.Dynamic, Property.IndexScope);
+        Setting.boolSetting(SETTING_SHARED_FS_ALLOW_RECOVERY_ON_ANY_NODE, false,
+            Property.Dynamic, Property.IndexScope, Property.Deprecated);
     public static final String INDEX_UUID_NA_VALUE = "_na_";
 
     public static final String INDEX_ROUTING_REQUIRE_GROUP_PREFIX = "index.routing.allocation.require";
@@ -1217,6 +1218,7 @@ public static IndexMetaData fromXContent(XContentParser parser) throws IOExcepti
      * {@link #isIndexUsingShadowReplicas(org.elasticsearch.common.settings.Settings)}.
      */
     public static boolean isOnSharedFilesystem(Settings settings) {
+        // don't use the setting directly, not to trigger verbose deprecation logging
         return settings.getAsBoolean(SETTING_SHARED_FILESYSTEM, isIndexUsingShadowReplicas(settings));
     }
 
@@ -1226,6 +1228,7 @@ public static boolean isOnSharedFilesystem(Settings settings) {
      * setting for this is <code>false</code>.
      */
     public static boolean isIndexUsingShadowReplicas(Settings settings) {
+        // don't use the setting directly, not to trigger verbose deprecation logging
         return settings.getAsBoolean(SETTING_SHADOW_REPLICAS, false);
     }
 

core/src/main/java/org/elasticsearch/gateway/PrimaryShardAllocator.java

@@ -476,8 +476,10 @@ static NodeShardsResult buildVersionBasedNodeShardsResult(ShardRouting shard, bo
      * recovered on any node
      */
     private boolean recoverOnAnyNode(IndexMetaData metaData) {
+        // don't use the setting directly, not to trigger verbose deprecation logging
         return (IndexMetaData.isOnSharedFilesystem(metaData.getSettings()) || IndexMetaData.isOnSharedFilesystem(this.settings))
-            && IndexMetaData.INDEX_SHARED_FS_ALLOW_RECOVERY_ON_ANY_NODE_SETTING.get(metaData.getSettings(), this.settings);
+            && (metaData.getSettings().getAsBoolean(IndexMetaData.SETTING_SHARED_FS_ALLOW_RECOVERY_ON_ANY_NODE, false) ||
+                this.settings.getAsBoolean(IndexMetaData.SETTING_SHARED_FS_ALLOW_RECOVERY_ON_ANY_NODE, false));
     }
 
     protected abstract FetchResult<NodeGatewayStartedShards> fetchData(ShardRouting shard, RoutingAllocation allocation);

core/src/test/java/org/elasticsearch/gateway/PrimaryShardAllocatorTests.java

@@ -76,6 +76,16 @@ public class PrimaryShardAllocatorTests extends ESAllocationTestCase {
     private final DiscoveryNode node3 = newNode("node3");
     private TestAllocator testAllocator;
 
+
+    /**
+     * needed due to random usage of {@link IndexMetaData#INDEX_SHARED_FS_ALLOW_RECOVERY_ON_ANY_NODE_SETTING}. removed once
+     * shadow replicas are removed.
+     */
+    @Override
+    protected boolean enableWarningsCheck() {
+        return false;
+    }
+
     @Before
     public void buildTestAllocator() {
         this.testAllocator = new TestAllocator();

core/src/test/java/org/elasticsearch/indices/cluster/IndicesClusterStateServiceRandomUpdatesTests.java

@@ -76,6 +76,15 @@ public class IndicesClusterStateServiceRandomUpdatesTests extends AbstractIndice
 
     private final ClusterStateChanges cluster = new ClusterStateChanges(xContentRegistry());
 
+    /**
+     * needed due to random usage of {@link IndexMetaData#INDEX_SHADOW_REPLICAS_SETTING}. removed once
+     * shadow replicas are removed.
+     */
+    @Override
+    protected boolean enableWarningsCheck() {
+        return false;
+    }
+
     public void testRandomClusterStateUpdates() {
         // we have an IndicesClusterStateService per node in the cluster
         final Map<DiscoveryNode, IndicesClusterStateService> clusterStateServiceMap = new HashMap<>();

docs/reference/indices/shadow-replicas.asciidoc

@@ -1,7 +1,7 @@
 [[indices-shadow-replicas]]
 == Shadow replica indices
 
-experimental[]
+deprecated[5.2.0, Shadow replicas don't see much usage and we are planning to remove them]
 
 If you would like to use a shared filesystem, you can use the shadow replicas
 settings to choose where on disk the data for an index should be kept, as well

docs/reference/migration/migrate_5_2.asciidoc

@@ -61,4 +61,8 @@ Please use the non-`source` methods instead (like `settings` and `type`).
 [float]
 ==== Timestamp meta-data field type for ingest processors has changed
 
-The type of the "timestamp" meta-data field for ingest processors has changed from `java.lang.String` to `java.util.Date`.
+The type of the "timestamp" meta-data field for ingest processors has changed from `java.lang.String` to `java.util.Date`.
+
+=== Shadow Replicas are deprecated
+
+<<indices-shadow-replicas,Shadow Replicas>> don't see much usage and we are planning to remove them.

rest-api-spec/src/main/resources/rest-api-spec/test/cat.shards/10_basic.yaml

@@ -165,6 +165,13 @@
       $body: |
                /^(index2 \s+ \d \s+ (p|r) \s+ ((STARTED|INITIALIZING|RELOCATING) \s+ (\d \s+ (\d+|\d+[.]\d+)(kb|b) \s+)? \d{1,3}.\d{1,3}.\d{1,3}.\d{1,3} \s+ .+|UNASSIGNED \s+) \n?){5}$/
 
+---
+"Test cat shards with shadow replicas":
+  - skip:
+      version: " - 6.99.99"
+      reason: deprecation was added in 5.2.0 (but this is disable now due to a bug in ThreadContext, Boaz is on it)
+      features: "warnings"
+
   - do:
       indices.create:
         index: index3
@@ -174,6 +181,9 @@
             number_of_replicas: "1"
             shadow_replicas: true
             shared_filesystem: false
+      warnings:
+        - "[index.shadow_replicas] setting was deprecated in Elasticsearch and it will be removed in a future release! See the breaking changes lists in the documentation for details"
+        - "[index.shared_filesystem] setting was deprecated in Elasticsearch and it will be removed in a future release! See the breaking changes lists in the documentation for details"
 
   - do:
       cat.shards: