Reliably refresh tablets after updating tablet files for a compaction.

core/src/main/java/org/apache/accumulo/core/metadata/RootTable.java

@@ -43,6 +43,10 @@ public class RootTable {
    * ZK path relative to the zookeeper node where the root tablet gc candidates are stored.
    */
   public static final String ZROOT_TABLET_GC_CANDIDATES = ZROOT_TABLET + "/gc_candidates";
+  /*
+   * ZK path relative to the zookeeper node where the root tablet refresh entries are stored.
+   */
+  public static final String ZROOT_TABLET_REFRESHES = ZROOT_TABLET + "/refreshes";
 
   public static final KeyExtent EXTENT = new KeyExtent(ID, null, null);
   public static final KeyExtent OLD_EXTENT =

core/src/main/java/org/apache/accumulo/core/metadata/schema/Ample.java

@@ -21,6 +21,7 @@
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.Map;
+import java.util.Objects;
 import java.util.UUID;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
@@ -593,4 +594,46 @@ default void addBulkLoadInProgressFlag(String path, long fateTxid) {
   default void removeBulkLoadInProgressFlag(String path) {
     throw new UnsupportedOperationException();
   }
+
+  interface Refreshes {
+    static class RefreshEntry {
+      private final ExternalCompactionId ecid;
+
+      private final KeyExtent extent;
+      private final TServerInstance tserver;
+
+      public RefreshEntry(ExternalCompactionId ecid, KeyExtent extent, TServerInstance tserver) {
+        this.ecid = Objects.requireNonNull(ecid);
+        this.extent = Objects.requireNonNull(extent);
+        this.tserver = Objects.requireNonNull(tserver);
+      }
+
+      public ExternalCompactionId getEcid() {
+        return ecid;
+      }
+
+      public KeyExtent getExtent() {
+        return extent;
+      }
+
+      public TServerInstance getTserver() {
+        return tserver;
+      }
+    }
+
+    void add(Collection<RefreshEntry> entries);
+
+    void delete(Collection<RefreshEntry> entries);
+
+    Stream<RefreshEntry> stream();
+  }
+
+  /**
+   * Refresh entries in the metadata table are used to track hosted tablets that need to have their
+   * metadata refreshed after a compaction. These entries ensure the refresh happens even in the
+   * case of process death.
+   */
+  default Refreshes refreshes(DataLevel dataLevel) {
+    throw new UnsupportedOperationException();
+  }
 }

core/src/main/java/org/apache/accumulo/core/metadata/schema/MetadataSchema.java

@@ -491,4 +491,17 @@ public static String getRowPrefix() {
       return section.getRowPrefix();
     }
   }
+
+  public static class RefreshSection {
+    private static final Section section =
+        new Section(RESERVED_PREFIX + "refresh", true, RESERVED_PREFIX + "refresi", false);
+
+    public static Range getRange() {
+      return section.getRange();
+    }
+
+    public static String getRowPrefix() {
+      return section.getRowPrefix();
+    }
+  }
 }