remove _primary and _replica shard preferences

The shard preference `_primary`, `_replica` and its variants were useful
for the asynchronous replication. However, with the current impl, they
are no longer useful and should be removed.

Closes elastic#26335

client/client-benchmark-noop-api-plugin/src/main/java/org/elasticsearch/plugin/noop/action/search/NoopSearchRequestBuilder.java

@@ -142,8 +142,8 @@ public NoopSearchRequestBuilder setRouting(String... routing) {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public NoopSearchRequestBuilder setPreference(String preference) {
         request.preference(preference);

core/src/main/java/org/elasticsearch/action/admin/cluster/shards/ClusterSearchShardsRequest.java

@@ -146,8 +146,8 @@ public ClusterSearchShardsRequest routing(String... routings) {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public ClusterSearchShardsRequest preference(String preference) {
         this.preference = preference;

core/src/main/java/org/elasticsearch/action/admin/cluster/shards/ClusterSearchShardsRequestBuilder.java

@@ -55,8 +55,8 @@ public ClusterSearchShardsRequestBuilder setRouting(String... routing) {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public ClusterSearchShardsRequestBuilder setPreference(String preference) {
         request.preference(preference);

core/src/main/java/org/elasticsearch/action/get/GetRequest.java

@@ -152,8 +152,8 @@ public GetRequest routing(String routing) {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public GetRequest preference(String preference) {
         this.preference = preference;

core/src/main/java/org/elasticsearch/action/get/GetRequestBuilder.java

@@ -76,8 +76,8 @@ public GetRequestBuilder setRouting(String routing) {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public GetRequestBuilder setPreference(String preference) {
         request.preference(preference);

core/src/main/java/org/elasticsearch/action/get/MultiGetRequest.java

@@ -284,8 +284,8 @@ public ActionRequestValidationException validate() {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public MultiGetRequest preference(String preference) {
         this.preference = preference;

core/src/main/java/org/elasticsearch/action/get/MultiGetRequestBuilder.java

@@ -58,8 +58,8 @@ public MultiGetRequestBuilder add(MultiGetRequest.Item item) {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public MultiGetRequestBuilder setPreference(String preference) {
         request.preference(preference);

core/src/main/java/org/elasticsearch/action/get/MultiGetShardRequest.java

@@ -64,8 +64,8 @@ public int shardId() {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public MultiGetShardRequest preference(String preference) {
         this.preference = preference;

core/src/main/java/org/elasticsearch/action/search/SearchRequest.java

@@ -241,8 +241,8 @@ public SearchRequest routing(String... routings) {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public SearchRequest preference(String preference) {
         this.preference = preference;

core/src/main/java/org/elasticsearch/action/search/SearchRequestBuilder.java

@@ -144,8 +144,8 @@ public SearchRequestBuilder setRouting(String... routing) {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public SearchRequestBuilder setPreference(String preference) {
         request.preference(preference);

core/src/main/java/org/elasticsearch/action/termvectors/MultiTermVectorsShardRequest.java

@@ -59,8 +59,8 @@ public int shardId() {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public MultiTermVectorsShardRequest preference(String preference) {
         this.preference = preference;

core/src/main/java/org/elasticsearch/action/termvectors/TermVectorsRequest.java

@@ -294,8 +294,7 @@ public String preference() {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across
-     * shards. Can be set to <tt>_local</tt> to prefer local shards,
-     * <tt>_primary</tt> to execute only on primary shards, or a custom value,
+     * shards. Can be set to <tt>_local</tt> to prefer local shards or a custom value,
      * which guarantees that the same order will be used across different
      * requests.
      */

core/src/main/java/org/elasticsearch/action/termvectors/TermVectorsRequestBuilder.java

@@ -99,8 +99,8 @@ public TermVectorsRequestBuilder setParent(String parent) {
 
     /**
      * Sets the preference to execute the search. Defaults to randomize across shards. Can be set to
-     * <tt>_local</tt> to prefer local shards, <tt>_primary</tt> to execute only on primary shards, or
-     * a custom value, which guarantees that the same order will be used across different requests.
+     * <tt>_local</tt> to prefer local shards or a custom value, which guarantees that the same order
+     * will be used across different requests.
      */
     public TermVectorsRequestBuilder setPreference(String preference) {
         request.preference(preference);

core/src/main/java/org/elasticsearch/cluster/routing/IndexShardRoutingTable.java

@@ -441,74 +441,6 @@ public ShardIterator primaryShardIt() {
         return new PlainShardIterator(shardId, primaryAsList);
     }
 
-    public ShardIterator primaryActiveInitializingShardIt() {
-        if (noPrimariesActive()) {
-            return new PlainShardIterator(shardId, NO_SHARDS);
-        }
-        return primaryShardIt();
-    }
-
-    public ShardIterator primaryFirstActiveInitializingShardsIt() {
-        ArrayList<ShardRouting> ordered = new ArrayList<>(activeShards.size() + allInitializingShards.size());
-        // fill it in a randomized fashion
-        for (ShardRouting shardRouting : shuffler.shuffle(activeShards)) {
-            ordered.add(shardRouting);
-            if (shardRouting.primary()) {
-                // switch, its the matching node id
-                ordered.set(ordered.size() - 1, ordered.get(0));
-                ordered.set(0, shardRouting);
-            }
-        }
-        // no need to worry about primary first here..., its temporal
-        if (!allInitializingShards.isEmpty()) {
-            ordered.addAll(allInitializingShards);
-        }
-        return new PlainShardIterator(shardId, ordered);
-    }
-
-    public ShardIterator replicaActiveInitializingShardIt() {
-        // If the primaries are unassigned, return an empty list (there aren't
-        // any replicas to query anyway)
-        if (noPrimariesActive()) {
-            return new PlainShardIterator(shardId, NO_SHARDS);
-        }
-
-        LinkedList<ShardRouting> ordered = new LinkedList<>();
-        for (ShardRouting replica : shuffler.shuffle(replicas)) {
-            if (replica.active()) {
-                ordered.addFirst(replica);
-            } else if (replica.initializing()) {
-                ordered.addLast(replica);
-            }
-        }
-        return new PlainShardIterator(shardId, ordered);
-    }
-
-    public ShardIterator replicaFirstActiveInitializingShardsIt() {
-        // If the primaries are unassigned, return an empty list (there aren't
-        // any replicas to query anyway)
-        if (noPrimariesActive()) {
-            return new PlainShardIterator(shardId, NO_SHARDS);
-        }
-
-        ArrayList<ShardRouting> ordered = new ArrayList<>(activeShards.size() + allInitializingShards.size());
-        // fill it in a randomized fashion with the active replicas
-        for (ShardRouting replica : shuffler.shuffle(replicas)) {
-            if (replica.active()) {
-                ordered.add(replica);
-            }
-        }
-
-        // Add the primary shard
-        ordered.add(primary);
-
-        // Add initializing shards last
-        if (!allInitializingShards.isEmpty()) {
-            ordered.addAll(allInitializingShards);
-        }
-        return new PlainShardIterator(shardId, ordered);
-    }
-
     public ShardIterator onlyNodeActiveInitializingShardsIt(String nodeId) {
         ArrayList<ShardRouting> ordered = new ArrayList<>(activeShards.size() + allInitializingShards.size());
         int seed = shuffler.nextSeed();

core/src/main/java/org/elasticsearch/cluster/routing/OperationRouting.java

@@ -198,14 +198,6 @@ private ShardIterator preferenceActiveShardIterator(IndexShardRoutingTable index
                     return indexShard.preferNodeActiveInitializingShardsIt(nodesIds);
                 case LOCAL:
                     return indexShard.preferNodeActiveInitializingShardsIt(Collections.singleton(localNodeId));
-                case PRIMARY:
-                    return indexShard.primaryActiveInitializingShardIt();
-                case REPLICA:
-                    return indexShard.replicaActiveInitializingShardIt();
-                case PRIMARY_FIRST:
-                    return indexShard.primaryFirstActiveInitializingShardsIt();
-                case REPLICA_FIRST:
-                    return indexShard.replicaFirstActiveInitializingShardsIt();
                 case ONLY_LOCAL:
                     return indexShard.onlyNodeActiveInitializingShardsIt(localNodeId);
                 case ONLY_NODES:

core/src/main/java/org/elasticsearch/cluster/routing/Preference.java

@@ -39,26 +39,6 @@ public enum  Preference {
      */
     LOCAL("_local"),
 
-    /**
-     * Route to primary shards
-     */
-    PRIMARY("_primary"),
-
-    /**
-     * Route to replica shards
-     */
-    REPLICA("_replica"),
-
-    /**
-     * Route to primary shards first
-     */
-    PRIMARY_FIRST("_primary_first"),
-
-    /**
-     * Route to replica shards first
-     */
-    REPLICA_FIRST("_replica_first"),
-
     /**
      * Route to the local shard only
      */
@@ -97,16 +77,6 @@ public static Preference parse(String preference) {
                 return PREFER_NODES;
             case "_local":
                 return LOCAL;
-            case "_primary":
-                return PRIMARY;
-            case "_replica":
-                return REPLICA;
-            case "_primary_first":
-            case "_primaryFirst":
-                return PRIMARY_FIRST;
-            case "_replica_first":
-            case "_replicaFirst":
-                return REPLICA_FIRST;
             case "_only_local":
             case "_onlyLocal":
                 return ONLY_LOCAL;

core/src/test/java/org/elasticsearch/cluster/structure/RoutingIteratorTests.java

@@ -50,6 +50,7 @@
 import static java.util.Collections.unmodifiableMap;
 import static org.elasticsearch.cluster.routing.ShardRoutingState.INITIALIZING;
 import static org.hamcrest.Matchers.anyOf;
+import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.not;
 import static org.hamcrest.Matchers.notNullValue;
@@ -442,57 +443,15 @@ public void testReplicaShardPreferenceIters() throws Exception {
 
         clusterState = strategy.applyStartedShards(clusterState, clusterState.getRoutingNodes().shardsWithState(INITIALIZING));
 
-        // When replicas haven't initialized, it comes back with the primary first, then initializing replicas
-        GroupShardsIterator<ShardIterator> shardIterators = operationRouting.searchShards(clusterState, new String[]{"test"}, null, "_replica_first");
-        assertThat(shardIterators.size(), equalTo(2)); // two potential shards
-        ShardIterator iter = shardIterators.iterator().next();
-        assertThat(iter.size(), equalTo(3)); // three potential candidates for the shard
-        ShardRouting routing = iter.nextOrNull();
-        assertNotNull(routing);
-        assertThat(routing.shardId().id(), anyOf(equalTo(0), equalTo(1)));
-        assertTrue(routing.primary()); // replicas haven't initialized yet, so primary is first
-        assertTrue(routing.started());
-        routing = iter.nextOrNull();
-        assertThat(routing.shardId().id(), anyOf(equalTo(0), equalTo(1)));
-        assertFalse(routing.primary());
-        assertTrue(routing.initializing());
-        routing = iter.nextOrNull();
-        assertThat(routing.shardId().id(), anyOf(equalTo(0), equalTo(1)));
-        assertFalse(routing.primary());
-        assertTrue(routing.initializing());
-
-        clusterState = strategy.applyStartedShards(clusterState, clusterState.getRoutingNodes().shardsWithState(INITIALIZING));
-
-        clusterState = strategy.applyStartedShards(clusterState, clusterState.getRoutingNodes().shardsWithState(INITIALIZING));
-
-
-        shardIterators = operationRouting.searchShards(clusterState, new String[]{"test"}, null, "_replica");
-        assertThat(shardIterators.size(), equalTo(2)); // two potential shards
-        iter = shardIterators.iterator().next();
-        assertThat(iter.size(), equalTo(2)); // two potential replicas for the shard
-        routing = iter.nextOrNull();
-        assertNotNull(routing);
-        assertThat(routing.shardId().id(), anyOf(equalTo(0), equalTo(1)));
-        assertFalse(routing.primary());
-        routing = iter.nextOrNull();
-        assertThat(routing.shardId().id(), anyOf(equalTo(0), equalTo(1)));
-        assertFalse(routing.primary());
-
-        shardIterators = operationRouting.searchShards(clusterState, new String[]{"test"}, null, "_replica_first");
-        assertThat(shardIterators.size(), equalTo(2)); // two potential shards
-        iter = shardIterators.iterator().next();
-        assertThat(iter.size(), equalTo(3)); // three potential candidates for the shard
-        routing = iter.nextOrNull();
-        assertNotNull(routing);
-        assertThat(routing.shardId().id(), anyOf(equalTo(0), equalTo(1)));
-        assertFalse(routing.primary());
-        routing = iter.nextOrNull();
-        assertThat(routing.shardId().id(), anyOf(equalTo(0), equalTo(1)));
-        assertFalse(routing.primary());
-        // finally the primary
-        routing = iter.nextOrNull();
-        assertThat(routing.shardId().id(), anyOf(equalTo(0), equalTo(1)));
-        assertTrue(routing.primary());
+        String[] removedPreferences = {"_primary", "_primary_first", "_replica", "_replica_first"};
+        for (String pref : removedPreferences) {
+            try{
+                operationRouting.searchShards(clusterState, new String[]{"test"}, null, pref);
+                fail("Should have failed because the shard preference [" + pref + "] is removed.");
+            }catch (IllegalArgumentException ex){
+                assertThat(ex.getMessage(), containsString(pref));
+            }
+        }
     }
 
 }

core/src/test/java/org/elasticsearch/index/translog/TruncateTranslogIT.java

@@ -210,7 +210,9 @@ public void testCorruptTranslogTruncation() throws Exception {
         logger.info("--> starting the replica node to test recovery");
         internalCluster().startNode();
         ensureGreen("test");
-        assertHitCount(client().prepareSearch("test").setPreference("_replica").setQuery(matchAllQuery()).get(), numDocsToKeep);
+        for(String node : internalCluster().nodesInclude("test")){
+            assertHitCount(client().prepareSearch("test").setPreference("_only_nodes:"+ node).setQuery(matchAllQuery()).get(), numDocsToKeep);
+        }
         final RecoveryResponse recoveryResponse = client().admin().indices().prepareRecoveries("test").setActiveOnly(false).get();
         final RecoveryState replicaRecoveryState = recoveryResponse.shardRecoveryStates().get("test").stream()
             .filter(recoveryState -> recoveryState.getPrimary() == false).findFirst().get();
@@ -308,7 +310,9 @@ public void testCorruptTranslogTruncationOfReplica() throws Exception {
         logger.info("--> starting the replica node to test recovery");
         internalCluster().startNode();
         ensureGreen("test");
-        assertHitCount(client().prepareSearch("test").setPreference("_replica").setQuery(matchAllQuery()).get(), totalDocs);
+        for(String node : internalCluster().nodesInclude("test")){
+            assertHitCount(client().prepareSearch("test").setPreference("_only_nodes:"+node).setQuery(matchAllQuery()).get(), totalDocs);
+        }
 
         final RecoveryResponse recoveryResponse = client().admin().indices().prepareRecoveries("test").setActiveOnly(false).get();
         final RecoveryState replicaRecoveryState = recoveryResponse.shardRecoveryStates().get("test").stream()

core/src/test/java/org/elasticsearch/indices/state/RareClusterStateIT.java

@@ -406,8 +406,7 @@ public void onFailure(Exception e) {
             }
         });
 
-        // Wait for document to be indexed on primary
-        assertBusy(() -> assertTrue(client().prepareGet("index", "type", "1").setPreference("_primary").get().isExists()));
+        assertBusy(() -> assertTrue(client().prepareGet("index", "type", "1").get().isExists()));
 
         // The mappings have not been propagated to the replica yet as a consequence the document count not be indexed
         // We wait on purpose to make sure that the document is not indexed because the shard operation is stalled