Add column replication_factor column to sys.segments table (#14403)

Description:
Druid allows a configuration of load rules that may cause a used segment to not be loaded
on any historical. This status is not tracked in the sys.segments table on the broker, which
makes it difficult to determine if the unavailability of a segment is expected and if we should
not wait for it to be loaded on a server after ingestion has finished.

Changes:
- Track replication factor in `SegmentReplicantLookup` during evaluation of load rules
- Update API `/druid/coordinator/v1metadata/segments` to return replication factor
- Add column `replication_factor` to the sys.segments virtual table and populate it in
`MetadataSegmentView`
- If this column is 0, the segment is not assigned to any historical and will not be loaded.

docs/api-reference/api-reference.md

@@ -173,11 +173,11 @@ Returns a list of all segments for one or more specific datasources enabled in t
 
 `GET /druid/coordinator/v1/metadata/segments?includeOvershadowedStatus`
 
-Returns a list of all segments for each datasource with the full segment metadata and an extra field `overshadowed`.
+Returns a list of all segments for each datasource with the full segment metadata and extra fields `overshadowed` and `replicationFactor`.
 
 `GET /druid/coordinator/v1/metadata/segments?includeOvershadowedStatus&datasources={dataSourceName1}&datasources={dataSourceName2}`
 
-Returns a list of all segments for one or more specific datasources with the full segment metadata and an extra field `overshadowed`.
+Returns a list of all segments for one or more specific datasources with the full segment metadata and extra fields `overshadowed` and `replicationFactor`.
 
 `GET /druid/coordinator/v1/metadata/datasources`
 

docs/querying/sql-metadata-tables.md

@@ -157,6 +157,7 @@ Segments table provides details on all Druid segments, whether they are publishe
 |dimensions|VARCHAR|JSON-serialized form of the segment dimensions|
 |metrics|VARCHAR|JSON-serialized form of the segment metrics|
 |last_compaction_state|VARCHAR|JSON-serialized form of the compaction task's config (compaction task which created this segment). May be null if segment was not created by compaction task.|
+|replication_factor|BIGINT|Total number of replicas of the segment that are required to be loaded across all historical tiers, based on the load rule that currently applies to this segment. If this value is 0, the segment is not assigned to any historical and will not be loaded. This value is -1 if load rules for the segment have not been evaluated yet.|
 
 For example, to retrieve all currently active segments for datasource "wikipedia", use the query:
 

integration-tests/src/test/resources/results/auth_test_sys_schema_segments.json

@@ -17,6 +17,7 @@
     "shard_spec": "{\"type\":\"none\"}",
     "dimensions": "[\"anonymous\",\"area_code\",\"city\",\"continent_code\",\"country_name\",\"dma_code\",\"geo\",\"language\",\"namespace\",\"network\",\"newpage\",\"page\",\"postal_code\",\"region_lookup\",\"robot\",\"unpatrolled\",\"user\"]",
     "metrics": "[\"added\",\"count\",\"deleted\",\"delta\",\"delta_hist\",\"unique_users\",\"variation\"]",
-    "last_compaction_state": null
+    "last_compaction_state": null,
+    "replication_factor": 2
   }
 ]

processing/src/main/java/org/apache/druid/timeline/SegmentStatusInCluster.java

@@ -23,39 +23,55 @@ import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonUnwrapped;
 
+import javax.annotation.Nullable;
+import java.util.Objects;
+
 /**
- * DataSegment object plus the overshadowed status for the segment. An immutable object.
+ * This class represents the current state of a segment in the cluster and encapsulates the following:
- *
+ * <ul>
- * SegmentWithOvershadowedStatus's {@link #compareTo} method considers only the {@link SegmentId}
+ *   <li>the {@code DataSegment} object</li>
- * of the DataSegment object.
+ *   <li>overshadowed status of the segment</li>
+ *   <li>replication factor of the segment</li>
+ * </ul>
+ * <br></br>
+ * Objects of this class are used to sync the state of segments from the Coordinator to different services, typically the Broker.
+ * The {@link #compareTo} method considers only the {@link SegmentId}.
  */
-public class SegmentWithOvershadowedStatus implements Comparable<SegmentWithOvershadowedStatus>
+public class SegmentStatusInCluster implements Comparable<SegmentStatusInCluster>
 {
   private final boolean overshadowed;
+  /**
+   * The replication factor for the segment added across all tiers. This value is null if the load rules for
+   * the segment have not been evaluated yet.
+   */
+  private final Integer replicationFactor;
   /**
    * dataSegment is serialized "unwrapped", i.e. it's properties are included as properties of
-   * enclosing class. If in future, if {@code SegmentWithOvershadowedStatus} were to extend {@link DataSegment},
+   * enclosing class. If in the future, if {@code SegmentStatusInCluster} were to extend {@link DataSegment},
    * there will be no change in the serialized format.
    */
   @JsonUnwrapped
   private final DataSegment dataSegment;
 
   @JsonCreator
-  public SegmentWithOvershadowedStatus(
+  public SegmentStatusInCluster(
-      @JsonProperty("overshadowed") boolean overshadowed
+      @JsonProperty("overshadowed") boolean overshadowed,
+      @JsonProperty("replicationFactor") @Nullable Integer replicationFactor
   )
   {
     // Jackson will overwrite dataSegment if needed (even though the field is final)
-    this(null, overshadowed);
+    this(null, overshadowed, replicationFactor);
   }
 
-  public SegmentWithOvershadowedStatus(
+  public SegmentStatusInCluster(
       DataSegment dataSegment,
-      boolean overshadowed
+      boolean overshadowed,
+      Integer replicationFactor
   )
   {
     this.dataSegment = dataSegment;
     this.overshadowed = overshadowed;
+    this.replicationFactor = replicationFactor;
   }
 
   @JsonProperty
@@ -70,35 +86,36 @@ public class SegmentWithOvershadowedStatus implements Comparable<SegmentWithOver
     return dataSegment;
   }
 
+  @Nullable
+  @JsonProperty
+  public Integer getReplicationFactor()
+  {
+    return replicationFactor;
+  }
+
   @Override
   public boolean equals(Object o)
   {
     if (this == o) {
       return true;
     }
-    if (!(o instanceof SegmentWithOvershadowedStatus)) {
+    if (o == null || getClass() != o.getClass()) {
       return false;
     }
-    final SegmentWithOvershadowedStatus that = (SegmentWithOvershadowedStatus) o;
+    SegmentStatusInCluster that = (SegmentStatusInCluster) o;
-    if (!dataSegment.equals(that.dataSegment)) {
+    return overshadowed == that.overshadowed
-      return false;
+           && Objects.equals(replicationFactor, that.replicationFactor)
-    }
+           && Objects.equals(dataSegment, that.dataSegment);
-    if (overshadowed != (that.overshadowed)) {
-      return false;
-    }
-    return true;
   }
 
   @Override
   public int hashCode()
   {
-    int result = dataSegment.hashCode();
+    return Objects.hash(overshadowed, replicationFactor, dataSegment);
-    result = 31 * result + Boolean.hashCode(overshadowed);
-    return result;
   }
 
   @Override
-  public int compareTo(SegmentWithOvershadowedStatus o)
+  public int compareTo(SegmentStatusInCluster o)
   {
     return dataSegment.getId().compareTo(o.dataSegment.getId());
   }
@@ -106,8 +123,9 @@ public class SegmentWithOvershadowedStatus implements Comparable<SegmentWithOver
   @Override
   public String toString()
   {
-    return "SegmentWithOvershadowedStatus{" +
+    return "SegmentStatusInCluster{" +
            "overshadowed=" + overshadowed +
+           ", replicationFactor=" + replicationFactor +
            ", dataSegment=" + dataSegment +
            '}';
   }

processing/src/test/java/org/apache/druid/timeline/SegmentStatusInClusterTest.java

@@ -40,15 +40,17 @@ import javax.annotation.Nullable;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
-public class SegmentWithOvershadowedStatusTest
+public class SegmentStatusInClusterTest
 {
   private static final ObjectMapper MAPPER = createObjectMapper();
   private static final Interval INTERVAL = Intervals.of("2011-10-01/2011-10-02");
   private static final ImmutableMap<String, Object> LOAD_SPEC = ImmutableMap.of("something", "or_other");
   private static final boolean OVERSHADOWED = true;
+  private static final Integer REPLICATION_FACTOR = 2;
   private static final int TEST_VERSION = 0x9;
-  private static final SegmentWithOvershadowedStatus SEGMENT = createSegmentWithOvershadowedStatus();
+  private static final SegmentStatusInCluster SEGMENT = createSegmentForTest();
 
   private static ObjectMapper createObjectMapper()
   {
@@ -59,7 +61,7 @@ public class SegmentWithOvershadowedStatusTest
     return objectMapper;
   }
 
-  private static SegmentWithOvershadowedStatus createSegmentWithOvershadowedStatus()
+  private static SegmentStatusInCluster createSegmentForTest()
   {
     DataSegment dataSegment = new DataSegment(
         "something",
@@ -74,7 +76,7 @@ public class SegmentWithOvershadowedStatusTest
         1
     );
 
-    return new SegmentWithOvershadowedStatus(dataSegment, OVERSHADOWED);
+    return new SegmentStatusInCluster(dataSegment, OVERSHADOWED, REPLICATION_FACTOR);
   }
 
   @Test
@@ -85,7 +87,7 @@ public class SegmentWithOvershadowedStatusTest
         JacksonUtils.TYPE_REFERENCE_MAP_STRING_OBJECT
     );
 
-    Assert.assertEquals(11, objectMap.size());
+    Assert.assertEquals(12, objectMap.size());
     Assert.assertEquals("something", objectMap.get("dataSource"));
     Assert.assertEquals(INTERVAL.toString(), objectMap.get("interval"));
     Assert.assertEquals("1", objectMap.get("version"));
@@ -96,12 +98,13 @@ public class SegmentWithOvershadowedStatusTest
     Assert.assertEquals(TEST_VERSION, objectMap.get("binaryVersion"));
     Assert.assertEquals(1, objectMap.get("size"));
     Assert.assertEquals(OVERSHADOWED, objectMap.get("overshadowed"));
+    Assert.assertEquals(REPLICATION_FACTOR, objectMap.get("replicationFactor"));
 
     final String json = MAPPER.writeValueAsString(SEGMENT);
 
-    final TestSegmentWithOvershadowedStatus deserializedSegment = MAPPER.readValue(
+    final TestSegment deserializedSegment = MAPPER.readValue(
         json,
-        TestSegmentWithOvershadowedStatus.class
+        TestSegment.class
     );
 
     DataSegment dataSegment = SEGMENT.getDataSegment();
@@ -114,30 +117,33 @@ public class SegmentWithOvershadowedStatusTest
     Assert.assertEquals(dataSegment.getShardSpec(), deserializedSegment.getShardSpec());
     Assert.assertEquals(dataSegment.getSize(), deserializedSegment.getSize());
     Assert.assertEquals(dataSegment.getId(), deserializedSegment.getId());
+    Assert.assertEquals(OVERSHADOWED, deserializedSegment.isOvershadowed());
+    Assert.assertEquals(REPLICATION_FACTOR, deserializedSegment.getReplicationFactor());
   }
 
-  // Previously, the implementation of SegmentWithOvershadowedStatus had @JsonCreator/@JsonProperty and @JsonUnwrapped
+  // Previously, the implementation of SegmentStatusInCluster had @JsonCreator/@JsonProperty and @JsonUnwrapped
   // on the same field (dataSegment), which used to work in Jackson 2.6, but does not work with Jackson 2.9:
   // https://github.com/FasterXML/jackson-databind/issues/265#issuecomment-264344051
   @Test
   public void testJsonCreatorAndJsonUnwrappedAnnotationsAreCompatible() throws Exception
   {
     String json = MAPPER.writeValueAsString(SEGMENT);
-    SegmentWithOvershadowedStatus segment = MAPPER.readValue(json, SegmentWithOvershadowedStatus.class);
+    SegmentStatusInCluster segment = MAPPER.readValue(json, SegmentStatusInCluster.class);
     Assert.assertEquals(SEGMENT, segment);
     Assert.assertEquals(json, MAPPER.writeValueAsString(segment));
   }
 }
 
 /**
- * Subclass of DataSegment with overshadowed status
+ * Flat subclass of DataSegment for testing
  */
-class TestSegmentWithOvershadowedStatus extends DataSegment
+class TestSegment extends DataSegment
 {
   private final boolean overshadowed;
+  private final Integer replicationFactor;
 
   @JsonCreator
-  public TestSegmentWithOvershadowedStatus(
+  public TestSegment(
       @JsonProperty("dataSource") String dataSource,
       @JsonProperty("interval") Interval interval,
       @JsonProperty("version") String version,
@@ -154,7 +160,8 @@ class TestSegmentWithOvershadowedStatus extends DataSegment
       @JsonProperty("lasCompactionState") @Nullable CompactionState lastCompactionState,
       @JsonProperty("binaryVersion") Integer binaryVersion,
       @JsonProperty("size") long size,
-      @JsonProperty("overshadowed") boolean overshadowed
+      @JsonProperty("overshadowed") boolean overshadowed,
+      @JsonProperty("replicationFactor") Integer replicationFactor
   )
   {
     super(
@@ -170,6 +177,7 @@ class TestSegmentWithOvershadowedStatus extends DataSegment
         size
     );
     this.overshadowed = overshadowed;
+    this.replicationFactor = replicationFactor;
   }
 
   @JsonProperty
@@ -178,23 +186,31 @@ class TestSegmentWithOvershadowedStatus extends DataSegment
     return overshadowed;
   }
 
+  @JsonProperty
+  public Integer getReplicationFactor()
+  {
+    return replicationFactor;
+  }
+
   @Override
   public boolean equals(Object o)
   {
     if (this == o) {
       return true;
     }
-    if (!(o instanceof TestSegmentWithOvershadowedStatus)) {
+    if (o == null || getClass() != o.getClass()) {
       return false;
     }
     if (!super.equals(o)) {
       return false;
     }
-    final TestSegmentWithOvershadowedStatus that = (TestSegmentWithOvershadowedStatus) o;
+    TestSegment that = (TestSegment) o;
-    if (overshadowed != (that.overshadowed)) {
+    return overshadowed == that.overshadowed && Objects.equals(replicationFactor, that.replicationFactor);
-      return false;
-    }
-    return true;
   }
 
+  @Override
+  public int hashCode()
+  {
+    return Objects.hash(super.hashCode(), overshadowed, replicationFactor);
+  }
 }

server/src/main/java/org/apache/druid/server/coordinator/DruidCoordinator.java

@@ -154,6 +154,13 @@ public class DruidCoordinator
 
   private volatile boolean started = false;
   private volatile SegmentReplicantLookup segmentReplicantLookup = null;
+
+  /**
+   * Contains a map of segmentId to total replication factor across all tiers. This map is refreshed when load rules are
+   * evaluated. It is used by {@link DruidCoordinator} to supply this value to
+   * {@link org.apache.druid.server.http.MetadataResource}.
+   */
+  private volatile Object2IntMap<SegmentId> segmentIdToReplicationFactor = null;
   private volatile DruidCluster cluster = null;
 
   private int cachedBalancerThreadNumber;
@@ -817,6 +824,12 @@ public class DruidCoordinator
     return ImmutableList.of(compactSegments);
   }
 
+  @Nullable
+  public Integer getReplicationFactorForSegment(SegmentId segmentId)
+  {
+    return segmentIdToReplicationFactor == null ? null : segmentIdToReplicationFactor.getInt(segmentId);
+  }
+
   @VisibleForTesting
   protected class DutiesRunnable implements Runnable
   {
@@ -943,6 +956,13 @@ public class DruidCoordinator
             }
           }
         }
+
+        // Update the immutable replication factor map with latest values.
+        // This value is set here as it is recalculated during load rule evaluation.
+        if (params.getSegmentReplicantLookup() != null) {
+          segmentIdToReplicationFactor = params.getSegmentReplicantLookup().getSegmentIdToReplicationFactor();
+        }
+
         // Emit the runtime of the full DutiesRunnable
         params.getEmitter().emit(
             new ServiceMetricEvent.Builder()

server/src/main/java/org/apache/druid/server/coordinator/SegmentReplicantLookup.java

@@ -21,6 +21,8 @@ package org.apache.druid.server.coordinator;
 
 import com.google.common.collect.HashBasedTable;
 import com.google.common.collect.Table;
+import it.unimi.dsi.fastutil.objects.Object2IntMap;
+import it.unimi.dsi.fastutil.objects.Object2IntOpenHashMap;
 import it.unimi.dsi.fastutil.objects.Object2LongMap;
 import it.unimi.dsi.fastutil.objects.Object2LongOpenHashMap;
 import org.apache.druid.client.ImmutableDruidServer;
@@ -79,6 +81,7 @@ public class SegmentReplicantLookup
 
   private final Table<SegmentId, String, Integer> segmentsInCluster;
   private final Table<SegmentId, String, Integer> loadingSegments;
+  private final Map<SegmentId, Integer> segmentIdToReplicationFactor = new HashMap<>();
   private final DruidCluster cluster;
 
   private SegmentReplicantLookup(
@@ -114,6 +117,18 @@ public class SegmentReplicantLookup
     return (retVal == null) ? 0 : retVal;
   }
 
+  // TODO: Refactor this setter, as this class is following a singleton pattern with only getters, and this breaks convention.
+  // This would be revamped in https://github.com/apache/druid/pull/13197
+  public void setReplicationFactor(SegmentId segmentId, Integer requiredReplicas)
+  {
+    segmentIdToReplicationFactor.put(segmentId, requiredReplicas);
+  }
+
+  public Object2IntMap<SegmentId> getSegmentIdToReplicationFactor()
+  {
+    return new Object2IntOpenHashMap<>(segmentIdToReplicationFactor);
+  }
+
   private int getLoadingReplicants(SegmentId segmentId, String tier)
   {
     Integer retVal = loadingSegments.get(segmentId, tier);

server/src/main/java/org/apache/druid/server/coordinator/rules/LoadRule.java

@@ -77,6 +77,8 @@ public abstract class LoadRule implements Rule
       targetReplicants.putAll(getTieredReplicants());
       currentReplicants.putAll(params.getSegmentReplicantLookup().getClusterTiers(segment.getId()));
 
+      params.getSegmentReplicantLookup().setReplicationFactor(segment.getId(), getReplicationFactor());
+
       final CoordinatorStats stats = new CoordinatorStats();
       assign(params, segment, stats);
 
@@ -93,6 +95,11 @@ public abstract class LoadRule implements Rule
     }
   }
 
+  private int getReplicationFactor()
+  {
+    return getTieredReplicants().values().stream().reduce(0, Integer::sum);
+  }
+
   @Override
   public boolean canLoadSegments()
   {

server/src/main/java/org/apache/druid/server/http/MetadataResource.java

@@ -32,13 +32,14 @@ import org.apache.druid.indexing.overlord.IndexerMetadataStorageCoordinator;
 import org.apache.druid.indexing.overlord.Segments;
 import org.apache.druid.metadata.SegmentsMetadataManager;
 import org.apache.druid.server.JettyUtils;
+import org.apache.druid.server.coordinator.DruidCoordinator;
 import org.apache.druid.server.http.security.DatasourceResourceFilter;
 import org.apache.druid.server.security.AuthorizationUtils;
 import org.apache.druid.server.security.AuthorizerMapper;
 import org.apache.druid.server.security.ResourceAction;
 import org.apache.druid.timeline.DataSegment;
 import org.apache.druid.timeline.SegmentId;
-import org.apache.druid.timeline.SegmentWithOvershadowedStatus;
+import org.apache.druid.timeline.SegmentStatusInCluster;
 import org.joda.time.Interval;
 
 import javax.annotation.Nullable;
@@ -69,18 +70,21 @@ public class MetadataResource
   private final SegmentsMetadataManager segmentsMetadataManager;
   private final IndexerMetadataStorageCoordinator metadataStorageCoordinator;
   private final AuthorizerMapper authorizerMapper;
+  private final DruidCoordinator coordinator;
 
   @Inject
   public MetadataResource(
       SegmentsMetadataManager segmentsMetadataManager,
       IndexerMetadataStorageCoordinator metadataStorageCoordinator,
       AuthorizerMapper authorizerMapper,
+      DruidCoordinator coordinator,
       @Json ObjectMapper jsonMapper
   )
   {
     this.segmentsMetadataManager = segmentsMetadataManager;
     this.metadataStorageCoordinator = metadataStorageCoordinator;
     this.authorizerMapper = authorizerMapper;
+    this.coordinator = coordinator;
   }
 
   @GET
@@ -140,7 +144,7 @@ public class MetadataResource
   )
   {
     if (includeOvershadowedStatus != null) {
-      return getAllUsedSegmentsWithOvershadowedStatus(req, dataSources);
+      return getAllUsedSegmentsWithAdditionalDetails(req, dataSources);
     }
 
     Collection<ImmutableDruidDataSource> dataSourcesWithUsedSegments =
@@ -165,7 +169,7 @@ public class MetadataResource
     return builder.entity(authorizedSegments).build();
   }
 
-  private Response getAllUsedSegmentsWithOvershadowedStatus(
+  private Response getAllUsedSegmentsWithAdditionalDetails(
       HttpServletRequest req,
       @Nullable Set<String> dataSources
   )
@@ -184,15 +188,30 @@ public class MetadataResource
         .flatMap(t -> t.getSegments().stream());
     final Set<DataSegment> overshadowedSegments = dataSourcesSnapshot.getOvershadowedSegments();
 
-    final Stream<SegmentWithOvershadowedStatus> usedSegmentsWithOvershadowedStatus = usedSegments
+    final Stream<SegmentStatusInCluster> segmentStatus = usedSegments
-        .map(segment -> new SegmentWithOvershadowedStatus(segment, overshadowedSegments.contains(segment)));
+        .map(segment -> {
+          boolean isOvershadowed = overshadowedSegments.contains(segment);
+          Integer replicationFactor;
+          if (isOvershadowed) {
+            // If the segment is overshadowed, the replication factor won't be present in the coordinator, but we know
+            // that it should be 0 as we will unload it soon.
+            replicationFactor = 0;
+          } else {
+            replicationFactor = coordinator.getReplicationFactorForSegment(segment.getId());
+          }
+          return new SegmentStatusInCluster(
+                   segment,
+                   isOvershadowed,
+                   replicationFactor
+               );
+        });
 
-    final Function<SegmentWithOvershadowedStatus, Iterable<ResourceAction>> raGenerator = segment -> Collections
+    final Function<SegmentStatusInCluster, Iterable<ResourceAction>> raGenerator = segment -> Collections
         .singletonList(AuthorizationUtils.DATASOURCE_READ_RA_GENERATOR.apply(segment.getDataSegment().getDataSource()));
 
-    final Iterable<SegmentWithOvershadowedStatus> authorizedSegments = AuthorizationUtils.filterAuthorizedResources(
+    final Iterable<SegmentStatusInCluster> authorizedSegments = AuthorizationUtils.filterAuthorizedResources(
         req,
-        usedSegmentsWithOvershadowedStatus::iterator,
+        segmentStatus::iterator,
         raGenerator,
         authorizerMapper
     );

server/src/test/java/org/apache/druid/server/http/MetadataResourceTest.java

@@ -0,0 +1,172 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.server.http;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import org.apache.druid.client.DataSourcesSnapshot;
+import org.apache.druid.client.ImmutableDruidDataSource;
+import org.apache.druid.indexing.overlord.IndexerMetadataStorageCoordinator;
+import org.apache.druid.java.util.common.Intervals;
+import org.apache.druid.metadata.SegmentsMetadataManager;
+import org.apache.druid.server.coordinator.DruidCoordinator;
+import org.apache.druid.server.security.AuthConfig;
+import org.apache.druid.server.security.AuthTestUtils;
+import org.apache.druid.server.security.AuthenticationResult;
+import org.apache.druid.timeline.DataSegment;
+import org.apache.druid.timeline.SegmentStatusInCluster;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.ws.rs.core.Response;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+
+public class MetadataResourceTest
+{
+  private static final String DATASOURCE1 = "datasource1";
+  private static final String DATASOURCE2 = "datasource2";
+
+  private MetadataResource metadataResource;
+
+  private SegmentsMetadataManager segmentsMetadataManager;
+  private DruidCoordinator coordinator;
+  private HttpServletRequest request;
+
+  private final DataSegment dataSegment1 = new DataSegment(
+      DATASOURCE1,
+      Intervals.of("2010-01-01/P1D"),
+      "v0",
+      null,
+      null,
+      null,
+      null,
+      0x9,
+      10
+  );
+
+  private final DataSegment dataSegment2 = new DataSegment(
+      DATASOURCE1,
+      Intervals.of("2010-01-22/P1D"),
+      "v0",
+      null,
+      null,
+      null,
+      null,
+      0x9,
+      20
+  );
+
+  private final DataSegment dataSegment3 = new DataSegment(
+      DATASOURCE2,
+      Intervals.of("2010-01-01/P1M"),
+      "v0",
+      null,
+      null,
+      null,
+      null,
+      0x9,
+      30
+  );
+
+  private final DataSegment dataSegment4 = new DataSegment(
+      DATASOURCE2,
+      Intervals.of("2010-01-02/P1D"),
+      "v0",
+      null,
+      null,
+      null,
+      null,
+      0x9,
+      35
+  );
+
+  @Before
+  public void setUp()
+  {
+    request = mock(HttpServletRequest.class);
+    doReturn(mock(AuthenticationResult.class)).when(request).getAttribute(AuthConfig.DRUID_AUTHENTICATION_RESULT);
+
+    segmentsMetadataManager = mock(SegmentsMetadataManager.class);
+    ImmutableDruidDataSource druidDataSource1 = new ImmutableDruidDataSource(
+        DATASOURCE1,
+        ImmutableMap.of(),
+        ImmutableList.of(
+            dataSegment1,
+            dataSegment2
+        )
+    );
+
+    ImmutableDruidDataSource druidDataSource2 = new ImmutableDruidDataSource(
+        DATASOURCE1,
+        ImmutableMap.of(),
+        ImmutableList.of(
+            dataSegment3,
+            dataSegment4
+        )
+    );
+
+    DataSourcesSnapshot dataSourcesSnapshot = mock(DataSourcesSnapshot.class);
+    doReturn(dataSourcesSnapshot).when(segmentsMetadataManager).getSnapshotOfDataSourcesWithAllUsedSegments();
+    doReturn(ImmutableList.of(druidDataSource1, druidDataSource2)).when(dataSourcesSnapshot).getDataSourcesWithAllUsedSegments();
+
+    coordinator = mock(DruidCoordinator.class);
+    doReturn(2).when(coordinator).getReplicationFactorForSegment(dataSegment1.getId());
+    doReturn(null).when(coordinator).getReplicationFactorForSegment(dataSegment2.getId());
+    doReturn(1).when(coordinator).getReplicationFactorForSegment(dataSegment3.getId());
+    doReturn(1).when(coordinator).getReplicationFactorForSegment(dataSegment4.getId());
+    doReturn(ImmutableSet.of(dataSegment4)).when(dataSourcesSnapshot).getOvershadowedSegments();
+
+    metadataResource = new MetadataResource(segmentsMetadataManager, mock(IndexerMetadataStorageCoordinator.class), AuthTestUtils.TEST_AUTHORIZER_MAPPER, coordinator, new ObjectMapper());
+  }
+
+  @Test
+  public void testGetAllSegmentsWithOvershadowedStatus()
+  {
+    Response response = metadataResource.getAllUsedSegments(
+        request,
+        null,
+        "includeOvershadowedStatus"
+    );
+
+    List<SegmentStatusInCluster> resultList = materializeResponse(response);
+    Assert.assertEquals(resultList.size(), 4);
+    Assert.assertEquals(new SegmentStatusInCluster(dataSegment1, false, 2), resultList.get(0));
+    Assert.assertEquals(new SegmentStatusInCluster(dataSegment2, false, null), resultList.get(1));
+    Assert.assertEquals(new SegmentStatusInCluster(dataSegment3, false, 1), resultList.get(2));
+    // Replication factor should be 0 as the segment is overshadowed
+    Assert.assertEquals(new SegmentStatusInCluster(dataSegment4, true, 0), resultList.get(3));
+  }
+
+  private List<SegmentStatusInCluster> materializeResponse(Response response)
+  {
+    Iterable<SegmentStatusInCluster> resultIterator = (Iterable<SegmentStatusInCluster>) response.getEntity();
+    List<SegmentStatusInCluster> segmentStatusInClusters = new ArrayList<>();
+    resultIterator.forEach(segmentStatusInClusters::add);
+    return segmentStatusInClusters;
+  }
+}

sql/src/main/java/org/apache/druid/sql/calcite/schema/MetadataSegmentView.java

@@ -22,6 +22,8 @@ package org.apache.druid.sql.calcite.schema;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.base.Preconditions;
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
 import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.util.concurrent.Uninterruptibles;
 import com.google.inject.Inject;
@@ -40,7 +42,8 @@ import org.apache.druid.java.util.emitter.EmittingLogger;
 import org.apache.druid.metadata.SegmentsMetadataManager;
 import org.apache.druid.sql.calcite.planner.SegmentMetadataCacheConfig;
 import org.apache.druid.timeline.DataSegment;
-import org.apache.druid.timeline.SegmentWithOvershadowedStatus;
+import org.apache.druid.timeline.SegmentId;
+import org.apache.druid.timeline.SegmentStatusInCluster;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
 import java.util.Iterator;
@@ -76,7 +79,12 @@ public class MetadataSegmentView
    * from other threads.
    */
   @MonotonicNonNull
-  private volatile ImmutableSortedSet<SegmentWithOvershadowedStatus> publishedSegments = null;
+  private volatile ImmutableSortedSet<SegmentStatusInCluster> publishedSegments = null;
+  /**
+   * Caches the replication factor for segment IDs. In case of coordinator restarts or leadership re-elections, the coordinator API returns `null` replication factor until load rules are evaluated.
+   * The cache can be used during these periods to continue serving the previously fetched values.
+   */
+  private final Cache<SegmentId, Integer> segmentIdToReplicationFactor;
   private final ScheduledExecutorService scheduledExec;
   private final long pollPeriodInMS;
   private final LifecycleLock lifecycleLock = new LifecycleLock();
@@ -97,6 +105,9 @@ public class MetadataSegmentView
     this.isCacheEnabled = config.isMetadataSegmentCacheEnable();
     this.pollPeriodInMS = config.getMetadataSegmentPollPeriod();
     this.scheduledExec = Execs.scheduledSingleThreaded("MetadataSegmentView-Cache--%d");
+    this.segmentIdToReplicationFactor = CacheBuilder.newBuilder()
+                                                    .expireAfterAccess(10, TimeUnit.MINUTES)
+                                                    .build();
   }
 
   @LifecycleStart
@@ -133,27 +144,34 @@ public class MetadataSegmentView
   private void poll()
   {
     log.info("polling published segments from coordinator");
-    final JsonParserIterator<SegmentWithOvershadowedStatus> metadataSegments = getMetadataSegments(
+    final JsonParserIterator<SegmentStatusInCluster> metadataSegments = getMetadataSegments(
         coordinatorDruidLeaderClient,
         jsonMapper,
         segmentWatcherConfig.getWatchedDataSources()
     );
 
-    final ImmutableSortedSet.Builder<SegmentWithOvershadowedStatus> builder = ImmutableSortedSet.naturalOrder();
+    final ImmutableSortedSet.Builder<SegmentStatusInCluster> builder = ImmutableSortedSet.naturalOrder();
     while (metadataSegments.hasNext()) {
-      final SegmentWithOvershadowedStatus segment = metadataSegments.next();
+      final SegmentStatusInCluster segment = metadataSegments.next();
       final DataSegment interned = DataSegmentInterner.intern(segment.getDataSegment());
-      final SegmentWithOvershadowedStatus segmentWithOvershadowedStatus = new SegmentWithOvershadowedStatus(
+      Integer replicationFactor = segment.getReplicationFactor();
+      if (replicationFactor == null) {
+        replicationFactor = segmentIdToReplicationFactor.getIfPresent(segment.getDataSegment().getId());
+      } else {
+        segmentIdToReplicationFactor.put(segment.getDataSegment().getId(), segment.getReplicationFactor());
+      }
+      final SegmentStatusInCluster segmentStatusInCluster = new SegmentStatusInCluster(
           interned,
-          segment.isOvershadowed()
+          segment.isOvershadowed(),
+          replicationFactor
       );
-      builder.add(segmentWithOvershadowedStatus);
+      builder.add(segmentStatusInCluster);
     }
     publishedSegments = builder.build();
     cachePopulated.countDown();
   }
 
-  Iterator<SegmentWithOvershadowedStatus> getPublishedSegments()
+  Iterator<SegmentStatusInCluster> getPublishedSegments()
   {
     if (isCacheEnabled) {
       Uninterruptibles.awaitUninterruptibly(cachePopulated);
@@ -168,7 +186,7 @@ public class MetadataSegmentView
   }
 
   // Note that coordinator must be up to get segments
-  private JsonParserIterator<SegmentWithOvershadowedStatus> getMetadataSegments(
+  private JsonParserIterator<SegmentStatusInCluster> getMetadataSegments(
       DruidLeaderClient coordinatorClient,
       ObjectMapper jsonMapper,
       Set<String> watchedDataSources
@@ -188,7 +206,7 @@ public class MetadataSegmentView
 
     return SystemSchema.getThingsFromLeaderNode(
         query,
-        new TypeReference<SegmentWithOvershadowedStatus>()
+        new TypeReference<SegmentStatusInCluster>()
         {
         },
         coordinatorClient,

sql/src/main/java/org/apache/druid/sql/calcite/schema/SystemSchema.java

@@ -81,7 +81,7 @@ import org.apache.druid.sql.calcite.planner.PlannerContext;
 import org.apache.druid.sql.calcite.table.RowSignatures;
 import org.apache.druid.timeline.DataSegment;
 import org.apache.druid.timeline.SegmentId;
-import org.apache.druid.timeline.SegmentWithOvershadowedStatus;
+import org.apache.druid.timeline.SegmentStatusInCluster;
 import org.jboss.netty.handler.codec.http.HttpMethod;
 
 import javax.annotation.Nullable;
@@ -106,8 +106,8 @@ public class SystemSchema extends AbstractSchema
   private static final String TASKS_TABLE = "tasks";
   private static final String SUPERVISOR_TABLE = "supervisors";
 
-  private static final Function<SegmentWithOvershadowedStatus, Iterable<ResourceAction>>
+  private static final Function<SegmentStatusInCluster, Iterable<ResourceAction>>
-      SEGMENT_WITH_OVERSHADOWED_STATUS_RA_GENERATOR = segment ->
+      SEGMENT_STATUS_IN_CLUSTER_RA_GENERATOR = segment ->
       Collections.singletonList(AuthorizationUtils.DATASOURCE_READ_RA_GENERATOR.apply(
           segment.getDataSegment().getDataSource())
       );
@@ -117,6 +117,8 @@ public class SystemSchema extends AbstractSchema
           segment.getDataSource())
       );
 
+  private static final long REPLICATION_FACTOR_UNKNOWN = -1L;
+
   /**
    * Booleans constants represented as long type,
    * where 1 = true and 0 = false to make it easy to count number of segments
@@ -150,6 +152,7 @@ public class SystemSchema extends AbstractSchema
       .add("dimensions", ColumnType.STRING)
       .add("metrics", ColumnType.STRING)
       .add("last_compaction_state", ColumnType.STRING)
+      .add("replication_factor", ColumnType.LONG)
       .build();
 
   static final RowSignature SERVERS_SIGNATURE = RowSignature
@@ -288,7 +291,7 @@ public class SystemSchema extends AbstractSchema
 
       // Get published segments from metadata segment cache (if enabled in SQL planner config), else directly from
       // Coordinator.
-      final Iterator<SegmentWithOvershadowedStatus> metadataStoreSegments = metadataView.getPublishedSegments();
+      final Iterator<SegmentStatusInCluster> metadataStoreSegments = metadataView.getPublishedSegments();
 
       final Set<SegmentId> segmentsAlreadySeen = Sets.newHashSetWithExpectedSize(druidSchema.cache().getTotalSegments());
 
@@ -326,7 +329,10 @@ public class SystemSchema extends AbstractSchema
                   segment.getShardSpec() == null ? null : jsonMapper.writeValueAsString(segment.getShardSpec()),
                   segment.getDimensions() == null ? null : jsonMapper.writeValueAsString(segment.getDimensions()),
                   segment.getMetrics() == null ? null : jsonMapper.writeValueAsString(segment.getMetrics()),
-                  segment.getLastCompactionState() == null ? null : jsonMapper.writeValueAsString(segment.getLastCompactionState())
+                  segment.getLastCompactionState() == null ? null : jsonMapper.writeValueAsString(segment.getLastCompactionState()),
+                  // If the value is null, the load rules might have not evaluated yet, and we don't know the replication factor.
+                  // This should be automatically updated in the next refesh with Coordinator.
+                  val.getReplicationFactor() == null ? REPLICATION_FACTOR_UNKNOWN : (long) val.getReplicationFactor()
               };
             }
             catch (JsonProcessingException e) {
@@ -368,7 +374,8 @@ public class SystemSchema extends AbstractSchema
                   val.getValue().getSegment().getShardSpec() == null ? null : jsonMapper.writeValueAsString(val.getValue().getSegment().getShardSpec()),
                   val.getValue().getSegment().getDimensions() == null ? null : jsonMapper.writeValueAsString(val.getValue().getSegment().getDimensions()),
                   val.getValue().getSegment().getMetrics() == null ? null : jsonMapper.writeValueAsString(val.getValue().getSegment().getMetrics()),
-                  null // unpublished segments from realtime tasks will not be compacted yet
+                  null, // unpublished segments from realtime tasks will not be compacted yet
+                  REPLICATION_FACTOR_UNKNOWN // If the segment is unpublished, we won't have this information yet.
               };
             }
             catch (JsonProcessingException e) {
@@ -384,8 +391,8 @@ public class SystemSchema extends AbstractSchema
 
     }
 
-    private Iterator<SegmentWithOvershadowedStatus> getAuthorizedPublishedSegments(
+    private Iterator<SegmentStatusInCluster> getAuthorizedPublishedSegments(
-        Iterator<SegmentWithOvershadowedStatus> it,
+        Iterator<SegmentStatusInCluster> it,
         DataContext root
     )
     {
@@ -394,11 +401,11 @@ public class SystemSchema extends AbstractSchema
           "authenticationResult in dataContext"
       );
 
-      final Iterable<SegmentWithOvershadowedStatus> authorizedSegments = AuthorizationUtils
+      final Iterable<SegmentStatusInCluster> authorizedSegments = AuthorizationUtils
           .filterAuthorizedResources(
               authenticationResult,
               () -> it,
-              SEGMENT_WITH_OVERSHADOWED_STATUS_RA_GENERATOR,
+              SEGMENT_STATUS_IN_CLUSTER_RA_GENERATOR,
               authorizerMapper
           );
       return authorizedSegments.iterator();

sql/src/test/java/org/apache/druid/sql/calcite/schema/SystemSchemaTest.java

@@ -99,7 +99,7 @@ import org.apache.druid.sql.calcite.util.TestServerInventoryView;
 import org.apache.druid.timeline.CompactionState;
 import org.apache.druid.timeline.DataSegment;
 import org.apache.druid.timeline.SegmentId;
-import org.apache.druid.timeline.SegmentWithOvershadowedStatus;
+import org.apache.druid.timeline.SegmentStatusInCluster;
 import org.apache.druid.timeline.partition.NumberedShardSpec;
 import org.easymock.EasyMock;
 import org.jboss.netty.handler.codec.http.DefaultHttpResponse;
@@ -542,7 +542,7 @@ public class SystemSchemaTest extends CalciteTestBase
     final RelDataType rowType = segmentsTable.getRowType(new JavaTypeFactoryImpl());
     final List<RelDataTypeField> fields = rowType.getFieldList();
 
-    Assert.assertEquals(18, fields.size());
+    Assert.assertEquals(19, fields.size());
 
     final SystemSchema.TasksTable tasksTable = (SystemSchema.TasksTable) schema.getTableMap().get("tasks");
     final RelDataType sysRowType = tasksTable.getRowType(new JavaTypeFactoryImpl());
@@ -564,12 +564,12 @@ public class SystemSchemaTest extends CalciteTestBase
   public void testSegmentsTable() throws Exception
   {
     final SegmentsTable segmentsTable = new SegmentsTable(druidSchema, metadataView, new ObjectMapper(), authMapper);
-    final Set<SegmentWithOvershadowedStatus> publishedSegments = new HashSet<>(Arrays.asList(
+    final Set<SegmentStatusInCluster> publishedSegments = new HashSet<>(Arrays.asList(
-        new SegmentWithOvershadowedStatus(publishedCompactedSegment1, true),
+        new SegmentStatusInCluster(publishedCompactedSegment1, true, 2),
-        new SegmentWithOvershadowedStatus(publishedCompactedSegment2, false),
+        new SegmentStatusInCluster(publishedCompactedSegment2, false, 0),
-        new SegmentWithOvershadowedStatus(publishedUncompactedSegment3, false),
+        new SegmentStatusInCluster(publishedUncompactedSegment3, false, 2),
-        new SegmentWithOvershadowedStatus(segment1, true),
+        new SegmentStatusInCluster(segment1, true, 2),
-        new SegmentWithOvershadowedStatus(segment2, false)
+        new SegmentStatusInCluster(segment2, false, 0)
     ));
 
     EasyMock.expect(metadataView.getPublishedSegments()).andReturn(publishedSegments.iterator()).once();
@@ -598,7 +598,8 @@ public class SystemSchemaTest extends CalciteTestBase
         1L, //is_available
         0L, //is_realtime
         1L, //is_overshadowed
-        null //is_compacted
+        null, //is_compacted
+        2L  // replication_factor
     );
 
     verifyRow(
@@ -612,7 +613,8 @@ public class SystemSchemaTest extends CalciteTestBase
         1L, //is_available
         0L, //is_realtime
         0L, //is_overshadowed,
-        null //is_compacted
+        null, //is_compacted
+        0L  // replication_factor
     );
 
     //segment test3 is unpublished and has a NumberedShardSpec with partitionNum = 2
@@ -627,7 +629,8 @@ public class SystemSchemaTest extends CalciteTestBase
         1L, //is_available
         0L, //is_realtime
         0L, //is_overshadowed
-        null //is_compacted
+        null, //is_compacted
+        -1L   // replication_factor
     );
 
     verifyRow(
@@ -641,7 +644,8 @@ public class SystemSchemaTest extends CalciteTestBase
         1L, //is_available
         1L, //is_realtime
         0L, //is_overshadowed
-        null //is_compacted
+        null, //is_compacted
+        -1L  // replication_factor
     );
 
     verifyRow(
@@ -655,7 +659,8 @@ public class SystemSchemaTest extends CalciteTestBase
         1L, //is_available
         1L, //is_realtime
         0L, //is_overshadowed
-        null //is_compacted
+        null, //is_compacted
+        -1L  // replication_factor
     );
 
     // wikipedia segments are published and unavailable, num_replicas is 0
@@ -671,7 +676,8 @@ public class SystemSchemaTest extends CalciteTestBase
         0L, //is_available
         0L, //is_realtime
         1L, //is_overshadowed
-        expectedCompactionState //is_compacted
+        expectedCompactionState, //is_compacted
+        2L  // replication_factor
     );
 
     verifyRow(
@@ -685,7 +691,8 @@ public class SystemSchemaTest extends CalciteTestBase
         0L, //is_available
         0L, //is_realtime
         0L, //is_overshadowed
-        expectedCompactionState //is_compacted
+        expectedCompactionState, //is_compacted
+        0L  // replication_factor
     );
 
     verifyRow(
@@ -699,7 +706,8 @@ public class SystemSchemaTest extends CalciteTestBase
         0L, //is_available
         0L, //is_realtime
         0L, //is_overshadowed
-        null //is_compacted
+        null, //is_compacted
+        2L  // replication_factor
     );
 
     // Verify value types.
@@ -717,7 +725,8 @@ public class SystemSchemaTest extends CalciteTestBase
       long isAvailable,
       long isRealtime,
       long isOvershadowed,
-      CompactionState compactionState
+      CompactionState compactionState,
+      long replicationFactor
   ) throws Exception
   {
     Assert.assertEquals(segmentId, row[0].toString());
@@ -740,6 +749,7 @@ public class SystemSchemaTest extends CalciteTestBase
     } else {
       Assert.assertEquals(mapper.writeValueAsString(compactionState), row[17]);
     }
+    Assert.assertEquals(replicationFactor, row[18]);
   }
 
   @Test

website/.spelling

@@ -644,6 +644,7 @@ num_segments
 partition_num
 plaintext_port
 queue_insertion_time
+replication_factor
 runner_status
 segment_id
 server_type