HBASE-16092 Procedure v2 - complete child procedure support

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/Procedure.java

@@ -589,6 +589,11 @@ public abstract class Procedure<TEnvironment> implements Comparable<Procedure> {
     return --childrenLatch == 0;
   }
 
+  @InterfaceAudience.Private
+  protected synchronized boolean hasChildren() {
+    return childrenLatch > 0;
+  }
+
   /**
    * Called by the RootProcedureState on procedure execution.
    * Each procedure store its stack-index positions.
@@ -606,7 +611,7 @@ public abstract class Procedure<TEnvironment> implements Comparable<Procedure> {
 
   @InterfaceAudience.Private
   protected synchronized boolean removeStackIndex() {
-    if (stackIndexes.length > 1) {
+    if (stackIndexes != null && stackIndexes.length > 1) {
       stackIndexes = Arrays.copyOf(stackIndexes, stackIndexes.length - 1);
       return false;
     } else {

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/ProcedureExecutor.java

@@ -18,16 +18,18 @@
 
 package org.apache.hadoop.hbase.procedure2;
 
+import com.google.common.base.Preconditions;
+
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
-import java.util.HashSet;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
@@ -55,8 +57,6 @@ import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
 import org.apache.hadoop.hbase.util.NonceKey;
 import org.apache.hadoop.hbase.util.Pair;
 
-import com.google.common.base.Preconditions;
-
 /**
  * Thread Pool that executes the submitted procedures.
  * The executor has a ProcedureStore associated.
@@ -314,7 +314,7 @@ public class ProcedureExecutor<TEnvironment> {
           corruptedCount++;
         }
         if (abortOnCorruption && corruptedCount > 0) {
-          throw new IOException("found " + corruptedCount + " procedures on replay");
+          throw new IOException("found " + corruptedCount + " corrupted procedure(s) on replay");
         }
       }
     });
@@ -388,10 +388,10 @@ public class ProcedureExecutor<TEnvironment> {
         continue;
       }
 
-      if (proc.hasParent() && !proc.isFinished()) {
+      if (proc.hasParent()) {
         Procedure parent = procedures.get(proc.getParentProcId());
         // corrupted procedures are handled later at step 3
-        if (parent != null) {
+        if (parent != null && !proc.isFinished()) {
           parent.incChildrenLatch();
         }
       }
@@ -403,6 +403,11 @@ public class ProcedureExecutor<TEnvironment> {
         case RUNNABLE:
           runnableList.add(proc);
           break;
+        case WAITING:
+          if (!proc.hasChildren()) {
+            runnableList.add(proc);
+          }
+          break;
         case WAITING_TIMEOUT:
           if (waitingSet == null) {
             waitingSet = new HashSet<Procedure>();
@@ -413,8 +418,8 @@ public class ProcedureExecutor<TEnvironment> {
           if (proc.hasException()) {
             // add the proc to the runnables to perform the rollback
             runnables.addBack(proc);
-            break;
           }
+          break;
         case ROLLEDBACK:
         case INITIALIZING:
           String msg = "Unexpected " + proc.getState() + " state for " + proc;
@@ -433,7 +438,7 @@ public class ProcedureExecutor<TEnvironment> {
       RootProcedureState procStack = entry.getValue();
       if (procStack.isValid()) continue;
 
-      for (Procedure proc: procStack.getSubprocedures()) {
+      for (Procedure proc: procStack.getSubproceduresStack()) {
         LOG.error("corrupted procedure: " + proc);
         procedures.remove(proc.getProcId());
         runnableList.remove(proc);
@@ -940,7 +945,7 @@ public class ProcedureExecutor<TEnvironment> {
       store.update(rootProc);
     }
 
-    List<Procedure> subprocStack = procStack.getSubprocedures();
+    List<Procedure> subprocStack = procStack.getSubproceduresStack();
     assert subprocStack != null : "Called rollback with no steps executed rootProc=" + rootProc;
 
     int stackTail = subprocStack.size();
@@ -1021,9 +1026,14 @@ public class ProcedureExecutor<TEnvironment> {
       if (proc.hasParent()) {
         store.delete(proc.getProcId());
         procedures.remove(proc.getProcId());
+      } else {
+        final long[] childProcIds = rollbackStack.get(proc.getProcId()).getSubprocedureIds();
+        if (childProcIds != null) {
+          store.delete(proc, childProcIds);
         } else {
           store.update(proc);
         }
+      }
     } else {
       store.update(proc);
     }
@@ -1102,6 +1112,7 @@ public class ProcedureExecutor<TEnvironment> {
               assert subproc.getState() == ProcedureState.INITIALIZING : subproc;
               subproc.setParentProcId(procedure.getProcId());
               subproc.setProcId(nextProcId());
+              procStack.addSubProcedure(subproc);
             }
 
             if (!procedure.isFailed()) {
@@ -1138,17 +1149,7 @@ public class ProcedureExecutor<TEnvironment> {
       }
 
       // Commit the transaction
-      if (subprocs != null && !procedure.isFailed()) {
+      updateStoreOnExec(procStack, procedure, subprocs);
-        if (LOG.isTraceEnabled()) {
-          LOG.trace("Store add " + procedure + " children " + Arrays.toString(subprocs));
-        }
-        store.insert(procedure, subprocs);
-      } else {
-        if (LOG.isTraceEnabled()) {
-          LOG.trace("Store update " + procedure);
-        }
-        store.update(procedure);
-      }
 
       // if the store is not running we are aborting
       if (!store.isRunning()) {
@@ -1198,6 +1199,34 @@ public class ProcedureExecutor<TEnvironment> {
     }
   }
 
+  private void updateStoreOnExec(final RootProcedureState procStack,
+      final Procedure procedure, final Procedure[] subprocs) {
+    if (subprocs != null && !procedure.isFailed()) {
+      if (LOG.isTraceEnabled()) {
+        LOG.trace("Store add " + procedure + " children " + Arrays.toString(subprocs));
+      }
+      store.insert(procedure, subprocs);
+    } else {
+      if (LOG.isTraceEnabled()) {
+        LOG.trace("Store update " + procedure);
+      }
+      if (procedure.isFinished() && !procedure.hasParent()) {
+        // remove child procedures
+        final long[] childProcIds = procStack.getSubprocedureIds();
+        if (childProcIds != null) {
+          store.delete(procedure, childProcIds);
+          for (int i = 0; i < childProcIds.length; ++i) {
+            procedures.remove(childProcIds[i]);
+          }
+        } else {
+          store.update(procedure);
+        }
+      } else {
+        store.update(procedure);
+      }
+    }
+  }
+
   private void handleInterruptedException(final Procedure proc, final InterruptedException e) {
     if (LOG.isTraceEnabled()) {
       LOG.trace("got an interrupt during " + proc + ". suspend and retry it later.", e);

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/RootProcedureState.java

@@ -19,7 +19,9 @@
 package org.apache.hadoop.hbase.procedure2;
 
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -49,7 +51,8 @@ class RootProcedureState {
     ROLLINGBACK,     // The Procedure failed and the execution was rolledback
   }
 
-  private ArrayList<Procedure> subprocedures = null;
+  private Set<Procedure> subprocs = null;
+  private ArrayList<Procedure> subprocStack = null;
   private State state = State.RUNNING;
   private int running = 0;
 
@@ -87,13 +90,23 @@ class RootProcedureState {
     state = State.FAILED;
   }
 
-  protected synchronized List<Procedure> getSubprocedures() {
+  protected synchronized long[] getSubprocedureIds() {
-    return subprocedures;
+    if (subprocs == null) return null;
+    int index = 0;
+    final long[] subIds = new long[subprocs.size()];
+    for (Procedure proc: subprocs) {
+      subIds[index++] = proc.getProcId();
+    }
+    return subIds;
+  }
+
+  protected synchronized List<Procedure> getSubproceduresStack() {
+    return subprocStack;
   }
 
   protected synchronized RemoteProcedureException getException() {
-    if (subprocedures != null) {
+    if (subprocStack != null) {
-      for (Procedure proc: subprocedures) {
+      for (Procedure proc: subprocStack) {
         if (proc.hasException()) {
           return proc.getException();
         }
@@ -133,11 +146,19 @@ class RootProcedureState {
     if (proc.isFailed()) {
       state = State.FAILED;
     }
-    if (subprocedures == null) {
+    if (subprocStack == null) {
-      subprocedures = new ArrayList<Procedure>();
+      subprocStack = new ArrayList<Procedure>();
     }
-    proc.addStackIndex(subprocedures.size());
+    proc.addStackIndex(subprocStack.size());
-    subprocedures.add(proc);
+    subprocStack.add(proc);
+  }
+
+  protected synchronized void addSubProcedure(final Procedure proc) {
+    if (!proc.hasParent()) return;
+    if (subprocs == null) {
+      subprocs = new HashSet<Procedure>();
+    }
+    subprocs.add(proc);
   }
 
   /**
@@ -148,18 +169,19 @@ class RootProcedureState {
    * on load we recreate the full stack by aggregating each procedure stack-positions.
    */
   protected synchronized void loadStack(final Procedure proc) {
+    addSubProcedure(proc);
     int[] stackIndexes = proc.getStackIndexes();
     if (stackIndexes != null) {
-      if (subprocedures == null) {
+      if (subprocStack == null) {
-        subprocedures = new ArrayList<Procedure>();
+        subprocStack = new ArrayList<Procedure>();
       }
-      int diff = (1 + stackIndexes[stackIndexes.length - 1]) - subprocedures.size();
+      int diff = (1 + stackIndexes[stackIndexes.length - 1]) - subprocStack.size();
       if (diff > 0) {
-        subprocedures.ensureCapacity(1 + stackIndexes[stackIndexes.length - 1]);
+        subprocStack.ensureCapacity(1 + stackIndexes[stackIndexes.length - 1]);
-        while (diff-- > 0) subprocedures.add(null);
+        while (diff-- > 0) subprocStack.add(null);
       }
       for (int i = 0; i < stackIndexes.length; ++i) {
-        subprocedures.set(stackIndexes[i], proc);
+        subprocStack.set(stackIndexes[i], proc);
       }
     }
     if (proc.getState() == ProcedureState.ROLLEDBACK) {
@@ -173,8 +195,8 @@ class RootProcedureState {
    * Called on store load by the ProcedureExecutor to validate the procedure stack.
    */
   protected synchronized boolean isValid() {
-    if (subprocedures != null) {
+    if (subprocStack != null) {
-      for (Procedure proc: subprocedures) {
+      for (Procedure proc: subprocStack) {
         if (proc == null) {
           return false;
         }

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/store/NoopProcedureStore.java

@@ -70,4 +70,9 @@ public class NoopProcedureStore extends ProcedureStoreBase {
   public void delete(long procId) {
     // no-op
   }
+
+  @Override
+  public void delete(Procedure proc, long[] subprocs) {
+    // no-op
+  }
 }

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/store/ProcedureStore.java

@@ -20,9 +20,9 @@ package org.apache.hadoop.hbase.procedure2.store;
 
 import java.io.IOException;
 
+import org.apache.hadoop.hbase.ProcedureInfo;
 import org.apache.hadoop.hbase.classification.InterfaceAudience;
 import org.apache.hadoop.hbase.classification.InterfaceStability;
-import org.apache.hadoop.hbase.ProcedureInfo;
 import org.apache.hadoop.hbase.procedure2.Procedure;
 
 /**
@@ -188,4 +188,12 @@ public interface ProcedureStore {
    * @param procId the ID of the procedure to remove.
    */
   void delete(long procId);
+
+  /**
+   * The parent procedure completed.
+   * Update the state and mark all the child deleted.
+   * @param parentProc the parent procedure to serialize and write to the store.
+   * @param subProcIds the IDs of the sub-procedure to remove.
+   */
+  void delete(Procedure parentProc, long[] subProcIds);
 }

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/store/ProcedureStoreTracker.java

@@ -21,6 +21,7 @@ package org.apache.hadoop.hbase.procedure2.store;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.util.Arrays;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.TreeMap;
@@ -394,6 +395,14 @@ public class ProcedureStoreTracker {
     trackProcIds(procId);
   }
 
+  public void delete(long[] procIds) {
+    // TODO: optimize
+    Arrays.sort(procIds);
+    for (int i = 0; i < procIds.length; ++i) {
+      delete(procIds[i]);
+    }
+  }
+
   private void trackProcIds(long procId) {
     minUpdatedProcId = Math.min(minUpdatedProcId, procId);
     maxUpdatedProcId = Math.max(maxUpdatedProcId, procId);

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/store/wal/ProcedureWALFormat.java

@@ -18,6 +18,8 @@
 
 package org.apache.hadoop.hbase.procedure2.store.wal;
 
+import com.google.protobuf.InvalidProtocolBufferException;
+
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -36,8 +38,6 @@ import org.apache.hadoop.hbase.protobuf.generated.ProcedureProtos.ProcedureWALEn
 import org.apache.hadoop.hbase.protobuf.generated.ProcedureProtos.ProcedureWALHeader;
 import org.apache.hadoop.hbase.protobuf.generated.ProcedureProtos.ProcedureWALTrailer;
 
-import com.google.protobuf.InvalidProtocolBufferException;
-
 /**
  * Helper class that contains the WAL serialization utils.
  */
@@ -231,4 +231,18 @@ public final class ProcedureWALFormat {
     builder.setProcId(procId);
     builder.build().writeDelimitedTo(slot);
   }
+
+  public static void writeDelete(ByteSlot slot, Procedure proc, long[] subprocs)
+      throws IOException {
+    ProcedureWALEntry.Builder builder = ProcedureWALEntry.newBuilder();
+    builder.setType(ProcedureWALEntry.Type.PROCEDURE_WAL_DELETE);
+    builder.setProcId(proc.getProcId());
+    if (subprocs != null) {
+      builder.addProcedure(Procedure.convert(proc));
+      for (int i = 0; i < subprocs.length; ++i) {
+        builder.addChildId(subprocs[i]);
+      }
+    }
+    builder.build().writeDelimitedTo(slot);
+  }
 }

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/store/wal/ProcedureWALFormatReader.java

@@ -18,6 +18,8 @@
 
 package org.apache.hadoop.hbase.procedure2.store.wal;
 
+import com.google.protobuf.InvalidProtocolBufferException;
+
 import java.io.IOException;
 
 import org.apache.commons.logging.Log;
@@ -33,8 +35,6 @@ import org.apache.hadoop.hbase.procedure2.store.ProcedureStoreTracker;
 import org.apache.hadoop.hbase.protobuf.generated.ProcedureProtos;
 import org.apache.hadoop.hbase.protobuf.generated.ProcedureProtos.ProcedureWALEntry;
 
-import com.google.protobuf.InvalidProtocolBufferException;
-
 /**
  * Helper class that loads the procedures stored in a WAL
  */
@@ -209,15 +209,34 @@ public class ProcedureWALFormatReader {
   }
 
   private void readDeleteEntry(final ProcedureWALEntry entry) throws IOException {
-    assert entry.getProcedureCount() == 0 : "Expected no procedures";
     assert entry.hasProcId() : "expected ProcID";
-    if (LOG.isTraceEnabled()) {
+
-      LOG.trace("read delete entry " + entry.getProcId());
+    if (entry.getChildIdCount() > 0) {
+      assert entry.getProcedureCount() == 1 : "Expected only one procedure";
+
+      // update the parent procedure
+      loadProcedure(entry, entry.getProcedure(0));
+
+      // remove the child procedures of entry.getProcId()
+      for (int i = 0, count = entry.getChildIdCount(); i < count; ++i) {
+        deleteEntry(entry.getChildId(i));
       }
-    maxProcId = Math.max(maxProcId, entry.getProcId());
+    } else {
-    localProcedureMap.remove(entry.getProcId());
+      assert entry.getProcedureCount() == 0 : "Expected no procedures";
-    assert !procedureMap.contains(entry.getProcId());
+
-    tracker.setDeleted(entry.getProcId(), true);
+      // delete the procedure
+      deleteEntry(entry.getProcId());
+    }
+  }
+
+  private void deleteEntry(final long procId) {
+    if (LOG.isTraceEnabled()) {
+      LOG.trace("delete entry " + procId);
+    }
+    maxProcId = Math.max(maxProcId, procId);
+    localProcedureMap.remove(procId);
+    assert !procedureMap.contains(procId);
+    tracker.setDeleted(procId, true);
   }
 
   private boolean isDeleted(final long procId) {
@@ -269,6 +288,8 @@ public class ProcedureWALFormatReader {
 
     public boolean isCompleted() {
       if (!hasParent()) {
+        // we only consider 'root' procedures. because for the user 'completed'
+        // means when everything up to the 'root' is complete.
         switch (proto.getState()) {
           case ROLLEDBACK:
             return true;
@@ -294,7 +315,15 @@ public class ProcedureWALFormatReader {
 
     @Override
     public String toString() {
-      return "Entry(" + getProcId() + ", parentId=" + getParentId() + ")";
+      final StringBuilder sb = new StringBuilder();
+      sb.append("Entry(");
+      sb.append(getProcId());
+      sb.append(", parentId=");
+      sb.append(getParentId());
+      sb.append(", class=");
+      sb.append(proto.getClassName());
+      sb.append(")");
+      return sb.toString();
     }
   }
 
@@ -603,6 +632,22 @@ public class ProcedureWALFormatReader {
      * There is a gap between A stackIds so something was executed in between.
      */
     private boolean checkReadyToRun(Entry rootEntry) {
+      assert !rootEntry.hasParent() : "expected root procedure, got " + rootEntry;
+
+      if (rootEntry.isCompleted()) {
+        // if the root procedure is completed, sub-procedures should be gone
+        if (rootEntry.childHead != null) {
+          LOG.error("unexpected active children for root-procedure: " + rootEntry);
+          for (Entry p = rootEntry.childHead; p != null; p = p.linkNext) {
+            LOG.error("unexpected active children: " + p);
+          }
+        }
+
+        assert rootEntry.childHead == null : "unexpected children on root completion. " + rootEntry;
+        rootEntry.ready = true;
+        return true;
+      }
+
       int stackIdSum = 0;
       int maxStackId = 0;
       for (int i = 0; i < rootEntry.proto.getStackIdCount(); ++i) {

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/store/wal/WALProcedureStore.java

@@ -18,6 +18,8 @@
 
 package org.apache.hadoop.hbase.procedure2.store.wal;
 
+import com.google.common.annotations.VisibleForTesting;
+
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.util.ArrayList;
@@ -57,8 +59,6 @@ import org.apache.hadoop.hbase.protobuf.generated.ProcedureProtos.ProcedureWALHe
 import org.apache.hadoop.hbase.util.Threads;
 import org.apache.hadoop.ipc.RemoteException;
 
-import com.google.common.annotations.VisibleForTesting;
-
 /**
  * WAL implementation of the ProcedureStore.
  */
@@ -461,6 +461,29 @@ public class WALProcedureStore extends ProcedureStoreBase {
     }
   }
 
+  @Override
+  public void delete(final Procedure proc, final long[] subProcIds) {
+    if (LOG.isTraceEnabled()) {
+      LOG.trace("Update " + proc + " and Delete " + Arrays.toString(subProcIds));
+    }
+
+    ByteSlot slot = acquireSlot();
+    try {
+      // Serialize the delete
+      ProcedureWALFormat.writeDelete(slot, proc, subProcIds);
+
+      // Push the transaction data and wait until it is persisted
+      pushData(PushType.DELETE, slot, proc.getProcId(), subProcIds);
+    } catch (IOException e) {
+      // We are not able to serialize the procedure.
+      // this is a code error, and we are not able to go on.
+      LOG.fatal("Unable to serialize the procedure: " + proc, e);
+      throw new RuntimeException(e);
+    } finally {
+      releaseSlot(slot);
+    }
+  }
+
   private ByteSlot acquireSlot() {
     ByteSlot slot = slotsCache.poll();
     return slot != null ? slot : new ByteSlot();
@@ -544,7 +567,11 @@ public class WALProcedureStore extends ProcedureStoreBase {
         storeTracker.update(procId);
         break;
       case DELETE:
+        if (subProcIds != null && subProcIds.length > 0) {
+          storeTracker.delete(subProcIds);
+        } else {
           storeTracker.delete(procId);
+        }
         break;
       default:
         throw new RuntimeException("invalid push type " + type);

hbase-procedure/src/test/java/org/apache/hadoop/hbase/procedure2/ProcedureTestingUtility.java

@@ -39,6 +39,7 @@ import org.apache.hadoop.hbase.procedure2.store.ProcedureStore.ProcedureIterator
 import org.apache.hadoop.hbase.procedure2.store.NoopProcedureStore;
 import org.apache.hadoop.hbase.procedure2.store.wal.WALProcedureStore;
 import org.apache.hadoop.hbase.protobuf.generated.ErrorHandlingProtos.ForeignExceptionMessage;
+import org.apache.hadoop.hbase.protobuf.generated.ProcedureProtos.ProcedureState;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -232,6 +233,10 @@ public class ProcedureTestingUtility {
       addStackIndex(index);
     }
 
+    public void setFinishedState() {
+      setState(ProcedureState.FINISHED);
+    }
+
     @Override
     protected Procedure[] execute(Void env) { return null; }
 
@@ -250,7 +255,8 @@ public class ProcedureTestingUtility {
 
   public static class LoadCounter implements ProcedureStore.ProcedureLoader {
     private final ArrayList<Procedure> corrupted = new ArrayList<Procedure>();
-    private final ArrayList<Procedure> loaded = new ArrayList<Procedure>();
+    private final ArrayList<ProcedureInfo> completed = new ArrayList<ProcedureInfo>();
+    private final ArrayList<Procedure> runnable = new ArrayList<Procedure>();
 
     private Set<Long> procIds;
     private long maxProcId = 0;
@@ -269,7 +275,8 @@ public class ProcedureTestingUtility {
 
     public void reset(final Set<Long> procIds) {
       corrupted.clear();
-      loaded.clear();
+      completed.clear();
+      runnable.clear();
       this.procIds = procIds;
       this.maxProcId = 0;
     }
@@ -278,12 +285,24 @@ public class ProcedureTestingUtility {
       return maxProcId;
     }
 
-    public ArrayList<Procedure> getLoaded() {
+    public ArrayList<Procedure> getRunnables() {
-      return loaded;
+      return runnable;
+    }
+
+    public int getRunnableCount() {
+      return runnable.size();
+    }
+
+    public ArrayList<ProcedureInfo> getCompleted() {
+      return completed;
+    }
+
+    public int getCompletedCount() {
+      return completed.size();
     }
 
     public int getLoadedCount() {
-      return loaded.size();
+      return runnable.size() + completed.size();
     }
 
     public ArrayList<Procedure> getCorrupted() {
@@ -302,13 +321,21 @@ public class ProcedureTestingUtility {
     @Override
     public void load(ProcedureIterator procIter) throws IOException {
       while (procIter.hasNext()) {
+        long procId;
+        if (procIter.isNextCompleted()) {
+          ProcedureInfo proc = procIter.nextAsProcedureInfo();
+          procId = proc.getProcId();
+          LOG.debug("loading completed procId=" + procId + ": " + proc);
+          completed.add(proc);
+        } else {
           Procedure proc = procIter.nextAsProcedure();
-        LOG.debug("loading procId=" + proc.getProcId() + ": " + proc);
+          procId = proc.getProcId();
-        if (procIds != null) {
+          LOG.debug("loading runnable procId=" + procId + ": " + proc);
-          assertTrue("procId=" + proc.getProcId() + " unexpected",
+          runnable.add(proc);
-                     procIds.contains(proc.getProcId()));
+        }
+        if (procIds != null) {
+          assertTrue("procId=" + procId + " unexpected", procIds.contains(procId));
         }
-        loaded.add(proc);
       }
     }
 

hbase-procedure/src/test/java/org/apache/hadoop/hbase/procedure2/TestChildProcedures.java

@@ -0,0 +1,196 @@
+/**
+ * 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.hadoop.hbase.procedure2;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.CountDownLatch;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.FileStatus;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.HBaseCommonTestingUtility;
+import org.apache.hadoop.hbase.ProcedureInfo;
+import org.apache.hadoop.hbase.procedure2.store.ProcedureStore;
+import org.apache.hadoop.hbase.testclassification.SmallTests;
+import org.apache.hadoop.hbase.testclassification.MasterTests;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
+import org.apache.hadoop.hbase.util.Threads;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+@Category({MasterTests.class, SmallTests.class})
+public class TestChildProcedures {
+  private static final Log LOG = LogFactory.getLog(TestChildProcedures.class);
+
+  private static final int PROCEDURE_EXECUTOR_SLOTS = 1;
+
+  private static TestProcEnv procEnv;
+  private static ProcedureExecutor<TestProcEnv> procExecutor;
+  private static ProcedureStore procStore;
+  private static int procSleepInterval;
+
+  private HBaseCommonTestingUtility htu;
+  private FileSystem fs;
+  private Path testDir;
+  private Path logDir;
+
+  @Before
+  public void setUp() throws IOException {
+    htu = new HBaseCommonTestingUtility();
+    testDir = htu.getDataTestDir();
+    fs = testDir.getFileSystem(htu.getConfiguration());
+    assertTrue(testDir.depth() > 1);
+
+    logDir = new Path(testDir, "proc-logs");
+    procEnv = new TestProcEnv();
+    procStore = ProcedureTestingUtility.createStore(htu.getConfiguration(), fs, logDir);
+    procExecutor = new ProcedureExecutor(htu.getConfiguration(), procEnv, procStore);
+    procExecutor.testing = new ProcedureExecutor.Testing();
+    procStore.start(PROCEDURE_EXECUTOR_SLOTS);
+    procExecutor.start(PROCEDURE_EXECUTOR_SLOTS, true);
+    procSleepInterval = 0;
+  }
+
+  @After
+  public void tearDown() throws IOException {
+    procExecutor.stop();
+    procStore.stop(false);
+    fs.delete(logDir, true);
+  }
+
+  @Test
+  public void testChildLoad() throws Exception {
+    procEnv.toggleKillBeforeStoreUpdate = false;
+
+    TestRootProcedure proc = new TestRootProcedure();
+    long procId = ProcedureTestingUtility.submitAndWait(procExecutor, proc);
+    ProcedureTestingUtility.restart(procExecutor);
+    assertTrue("expected completed proc", procExecutor.isFinished(procId));
+    ProcedureTestingUtility.assertProcNotFailed(procExecutor, procId);
+  }
+
+  @Test
+  public void testChildLoadWithSteppedRestart() throws Exception {
+    procEnv.toggleKillBeforeStoreUpdate = true;
+
+    TestRootProcedure proc = new TestRootProcedure();
+    long procId = ProcedureTestingUtility.submitAndWait(procExecutor, proc);
+    int restartCount = 0;
+    while (!procExecutor.isFinished(procId)) {
+      ProcedureTestingUtility.restart(procExecutor);
+      restartCount++;
+    }
+    assertEquals(7, restartCount);
+    assertTrue("expected completed proc", procExecutor.isFinished(procId));
+    ProcedureTestingUtility.assertProcNotFailed(procExecutor, procId);
+  }
+
+  @Test
+  public void testChildRollbackLoad() throws Exception {
+    procEnv.toggleKillBeforeStoreUpdate = false;
+    procEnv.triggerRollbackOnChild = true;
+
+    TestRootProcedure proc = new TestRootProcedure();
+    long procId = ProcedureTestingUtility.submitAndWait(procExecutor, proc);
+    ProcedureTestingUtility.restart(procExecutor);
+
+    assertProcFailed(procId);
+  }
+
+  @Test
+  public void testChildRollbackLoadWithSteppedRestart() throws Exception {
+    procEnv.toggleKillBeforeStoreUpdate = true;
+    procEnv.triggerRollbackOnChild = true;
+
+    TestRootProcedure proc = new TestRootProcedure();
+    long procId = ProcedureTestingUtility.submitAndWait(procExecutor, proc);
+    int restartCount = 0;
+    while (!procExecutor.isFinished(procId)) {
+      ProcedureTestingUtility.restart(procExecutor);
+      restartCount++;
+    }
+    assertEquals(6, restartCount);
+    assertProcFailed(procId);
+  }
+
+  private void assertProcFailed(long procId) {
+    assertTrue("expected completed proc", procExecutor.isFinished(procId));
+    ProcedureInfo result = procExecutor.getResult(procId);
+    assertEquals(true, result.isFailed());
+    LOG.info(result.getExceptionFullMessage());
+  }
+
+  public static class TestRootProcedure extends SequentialProcedure<TestProcEnv> {
+    public TestRootProcedure() {}
+
+    public Procedure[] execute(TestProcEnv env) {
+      if (env.toggleKillBeforeStoreUpdate) {
+        ProcedureTestingUtility.toggleKillBeforeStoreUpdate(procExecutor);
+      }
+      return new Procedure[] { new TestChildProcedure(), new TestChildProcedure() };
+    }
+
+    public void rollback(TestProcEnv env) {
+    }
+
+    @Override
+    public boolean abort(TestProcEnv env) {
+      return false;
+    }
+  }
+
+  public static class TestChildProcedure extends SequentialProcedure<TestProcEnv> {
+    public TestChildProcedure() {}
+
+    public Procedure[] execute(TestProcEnv env) {
+      if (env.toggleKillBeforeStoreUpdate) {
+        ProcedureTestingUtility.toggleKillBeforeStoreUpdate(procExecutor);
+      }
+      if (env.triggerRollbackOnChild) {
+        setFailure("test", new Exception("test"));
+      }
+      return null;
+    }
+
+    public void rollback(TestProcEnv env) {
+    }
+
+    @Override
+    public boolean abort(TestProcEnv env) {
+      return false;
+    }
+  }
+
+  private static class TestProcEnv {
+    public boolean toggleKillBeforeStoreUpdate = false;
+    public boolean triggerRollbackOnChild = false;
+  }
+}

hbase-procedure/src/test/java/org/apache/hadoop/hbase/procedure2/store/wal/TestStressWALProcedureStore.java

@@ -106,7 +106,9 @@ public class TestStressWALProcedureStore {
           Random rand = new Random();
           TestProcedure proc;
           do {
-            proc = new TestProcedure(procCounter.addAndGet(1));
+            // After HBASE- there may be gap in the procId sequence, trying to simulate that.
+            long procId = procCounter.addAndGet(1 + rand.nextInt(3));
+            proc = new TestProcedure(procId);
             // Insert
             procStore.insert(proc, null);
             // Update

hbase-procedure/src/test/java/org/apache/hadoop/hbase/procedure2/store/wal/TestWALProcedureStore.java

@@ -33,6 +33,7 @@ import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.HBaseCommonTestingUtility;
+import org.apache.hadoop.hbase.ProcedureInfo;
 import org.apache.hadoop.hbase.procedure2.Procedure;
 import org.apache.hadoop.hbase.procedure2.ProcedureTestingUtility;
 import org.apache.hadoop.hbase.procedure2.ProcedureTestingUtility.LoadCounter;
@@ -506,10 +507,56 @@ public class TestWALProcedureStore {
     procStore.recoverLease();
     procStore.load(loader);
     assertEquals(procs.length, loader.getMaxProcId());
-    assertEquals(procs.length - 1, loader.getLoadedCount());
+    assertEquals(procs.length - 1, loader.getRunnableCount());
+    assertEquals(0, loader.getCompletedCount());
     assertEquals(0, loader.getCorruptedCount());
   }
 
+  public void testLoadChildren() throws Exception {
+    TestProcedure a = new TestProcedure(1, 0);
+    TestProcedure b = new TestProcedure(2, 1);
+    TestProcedure c = new TestProcedure(3, 1);
+
+    // INIT
+    procStore.insert(a, null);
+
+    // Run A first step
+    a.addStackId(0);
+    procStore.update(a);
+
+    // Run A second step
+    a.addStackId(1);
+    procStore.insert(a, new Procedure[] { b, c });
+
+    // Run B first step
+    b.addStackId(2);
+    procStore.update(b);
+
+    // Run C first and last step
+    c.addStackId(3);
+    procStore.update(c);
+
+    // Run B second setp
+    b.addStackId(4);
+    procStore.update(b);
+
+    // back to A
+    a.addStackId(5);
+    a.setFinishedState();
+    procStore.delete(a, new long[] { b.getProcId(), c.getProcId() });
+    restartAndAssert(3, 0, 1, 0);
+  }
+
+  private void restartAndAssert(long maxProcId, long runnableCount,
+      int completedCount, int corruptedCount) throws Exception {
+    final LoadCounter loader = new LoadCounter();
+    storeRestart(loader);
+    assertEquals(maxProcId, loader.getMaxProcId());
+    assertEquals(runnableCount, loader.getRunnableCount());
+    assertEquals(completedCount, loader.getCompletedCount());
+    assertEquals(corruptedCount, loader.getCorruptedCount());
+  }
+
   private void corruptLog(final FileStatus logFile, final long dropBytes)
       throws IOException {
     assertTrue(logFile.getLen() > dropBytes);

hbase-protocol/src/main/java/org/apache/hadoop/hbase/protobuf/generated/ProcedureProtos.java

@@ -6295,6 +6295,20 @@ public final class ProcedureProtos {
      * <code>optional uint64 proc_id = 3;</code>
      */
     long getProcId();
+
+    // repeated uint64 child_id = 4;
+    /**
+     * <code>repeated uint64 child_id = 4;</code>
+     */
+    java.util.List<java.lang.Long> getChildIdList();
+    /**
+     * <code>repeated uint64 child_id = 4;</code>
+     */
+    int getChildIdCount();
+    /**
+     * <code>repeated uint64 child_id = 4;</code>
+     */
+    long getChildId(int index);
   }
   /**
    * Protobuf type {@code hbase.pb.ProcedureWALEntry}
@@ -6371,6 +6385,27 @@ public final class ProcedureProtos {
               procId_ = input.readUInt64();
               break;
             }
+            case 32: {
+              if (!((mutable_bitField0_ & 0x00000008) == 0x00000008)) {
+                childId_ = new java.util.ArrayList<java.lang.Long>();
+                mutable_bitField0_ |= 0x00000008;
+              }
+              childId_.add(input.readUInt64());
+              break;
+            }
+            case 34: {
+              int length = input.readRawVarint32();
+              int limit = input.pushLimit(length);
+              if (!((mutable_bitField0_ & 0x00000008) == 0x00000008) && input.getBytesUntilLimit() > 0) {
+                childId_ = new java.util.ArrayList<java.lang.Long>();
+                mutable_bitField0_ |= 0x00000008;
+              }
+              while (input.getBytesUntilLimit() > 0) {
+                childId_.add(input.readUInt64());
+              }
+              input.popLimit(limit);
+              break;
+            }
           }
         }
       } catch (com.google.protobuf.InvalidProtocolBufferException e) {
@@ -6382,6 +6417,9 @@ public final class ProcedureProtos {
         if (((mutable_bitField0_ & 0x00000002) == 0x00000002)) {
           procedure_ = java.util.Collections.unmodifiableList(procedure_);
         }
+        if (((mutable_bitField0_ & 0x00000008) == 0x00000008)) {
+          childId_ = java.util.Collections.unmodifiableList(childId_);
+        }
         this.unknownFields = unknownFields.build();
         makeExtensionsImmutable();
       }
@@ -6600,10 +6638,34 @@ public final class ProcedureProtos {
       return procId_;
     }
 
+    // repeated uint64 child_id = 4;
+    public static final int CHILD_ID_FIELD_NUMBER = 4;
+    private java.util.List<java.lang.Long> childId_;
+    /**
+     * <code>repeated uint64 child_id = 4;</code>
+     */
+    public java.util.List<java.lang.Long>
+        getChildIdList() {
+      return childId_;
+    }
+    /**
+     * <code>repeated uint64 child_id = 4;</code>
+     */
+    public int getChildIdCount() {
+      return childId_.size();
+    }
+    /**
+     * <code>repeated uint64 child_id = 4;</code>
+     */
+    public long getChildId(int index) {
+      return childId_.get(index);
+    }
+
     private void initFields() {
       type_ = org.apache.hadoop.hbase.protobuf.generated.ProcedureProtos.ProcedureWALEntry.Type.PROCEDURE_WAL_EOF;
       procedure_ = java.util.Collections.emptyList();
       procId_ = 0L;
+      childId_ = java.util.Collections.emptyList();
     }
     private byte memoizedIsInitialized = -1;
     public final boolean isInitialized() {
@@ -6636,6 +6698,9 @@ public final class ProcedureProtos {
       if (((bitField0_ & 0x00000002) == 0x00000002)) {
         output.writeUInt64(3, procId_);
       }
+      for (int i = 0; i < childId_.size(); i++) {
+        output.writeUInt64(4, childId_.get(i));
+      }
       getUnknownFields().writeTo(output);
     }
 
@@ -6657,6 +6722,15 @@ public final class ProcedureProtos {
         size += com.google.protobuf.CodedOutputStream
           .computeUInt64Size(3, procId_);
       }
+      {
+        int dataSize = 0;
+        for (int i = 0; i < childId_.size(); i++) {
+          dataSize += com.google.protobuf.CodedOutputStream
+            .computeUInt64SizeNoTag(childId_.get(i));
+        }
+        size += dataSize;
+        size += 1 * getChildIdList().size();
+      }
       size += getUnknownFields().getSerializedSize();
       memoizedSerializedSize = size;
       return size;
@@ -6692,6 +6766,8 @@ public final class ProcedureProtos {
         result = result && (getProcId()
             == other.getProcId());
       }
+      result = result && getChildIdList()
+          .equals(other.getChildIdList());
       result = result &&
           getUnknownFields().equals(other.getUnknownFields());
       return result;
@@ -6717,6 +6793,10 @@ public final class ProcedureProtos {
         hash = (37 * hash) + PROC_ID_FIELD_NUMBER;
         hash = (53 * hash) + hashLong(getProcId());
       }
+      if (getChildIdCount() > 0) {
+        hash = (37 * hash) + CHILD_ID_FIELD_NUMBER;
+        hash = (53 * hash) + getChildIdList().hashCode();
+      }
       hash = (29 * hash) + getUnknownFields().hashCode();
       memoizedHashCode = hash;
       return hash;
@@ -6837,6 +6917,8 @@ public final class ProcedureProtos {
         }
         procId_ = 0L;
         bitField0_ = (bitField0_ & ~0x00000004);
+        childId_ = java.util.Collections.emptyList();
+        bitField0_ = (bitField0_ & ~0x00000008);
         return this;
       }
 
@@ -6882,6 +6964,11 @@ public final class ProcedureProtos {
           to_bitField0_ |= 0x00000002;
         }
         result.procId_ = procId_;
+        if (((bitField0_ & 0x00000008) == 0x00000008)) {
+          childId_ = java.util.Collections.unmodifiableList(childId_);
+          bitField0_ = (bitField0_ & ~0x00000008);
+        }
+        result.childId_ = childId_;
         result.bitField0_ = to_bitField0_;
         onBuilt();
         return result;
@@ -6930,6 +7017,16 @@ public final class ProcedureProtos {
         if (other.hasProcId()) {
           setProcId(other.getProcId());
         }
+        if (!other.childId_.isEmpty()) {
+          if (childId_.isEmpty()) {
+            childId_ = other.childId_;
+            bitField0_ = (bitField0_ & ~0x00000008);
+          } else {
+            ensureChildIdIsMutable();
+            childId_.addAll(other.childId_);
+          }
+          onChanged();
+        }
         this.mergeUnknownFields(other.getUnknownFields());
         return this;
       }
@@ -7276,6 +7373,72 @@ public final class ProcedureProtos {
         return this;
       }
 
+      // repeated uint64 child_id = 4;
+      private java.util.List<java.lang.Long> childId_ = java.util.Collections.emptyList();
+      private void ensureChildIdIsMutable() {
+        if (!((bitField0_ & 0x00000008) == 0x00000008)) {
+          childId_ = new java.util.ArrayList<java.lang.Long>(childId_);
+          bitField0_ |= 0x00000008;
+         }
+      }
+      /**
+       * <code>repeated uint64 child_id = 4;</code>
+       */
+      public java.util.List<java.lang.Long>
+          getChildIdList() {
+        return java.util.Collections.unmodifiableList(childId_);
+      }
+      /**
+       * <code>repeated uint64 child_id = 4;</code>
+       */
+      public int getChildIdCount() {
+        return childId_.size();
+      }
+      /**
+       * <code>repeated uint64 child_id = 4;</code>
+       */
+      public long getChildId(int index) {
+        return childId_.get(index);
+      }
+      /**
+       * <code>repeated uint64 child_id = 4;</code>
+       */
+      public Builder setChildId(
+          int index, long value) {
+        ensureChildIdIsMutable();
+        childId_.set(index, value);
+        onChanged();
+        return this;
+      }
+      /**
+       * <code>repeated uint64 child_id = 4;</code>
+       */
+      public Builder addChildId(long value) {
+        ensureChildIdIsMutable();
+        childId_.add(value);
+        onChanged();
+        return this;
+      }
+      /**
+       * <code>repeated uint64 child_id = 4;</code>
+       */
+      public Builder addAllChildId(
+          java.lang.Iterable<? extends java.lang.Long> values) {
+        ensureChildIdIsMutable();
+        super.addAll(values, childId_);
+        onChanged();
+        return this;
+      }
+      /**
+       * <code>repeated uint64 child_id = 4;</code>
+       */
+      public Builder clearChildId() {
+        childId_ = java.util.Collections.emptyList();
+        bitField0_ = (bitField0_ & ~0x00000008);
+        onChanged();
+        return this;
+      }
+
       // @@protoc_insertion_point(builder_scope:hbase.pb.ProcedureWALEntry)
     }
 
@@ -7355,19 +7518,19 @@ public final class ProcedureProtos {
       "eTracker\0229\n\004node\030\001 \003(\0132+.hbase.pb.Proced" +
       "ureStoreTracker.TrackerNode\032A\n\013TrackerNo" +
       "de\022\020\n\010start_id\030\001 \002(\004\022\017\n\007updated\030\002 \003(\004\022\017\n" +
-      "\007deleted\030\003 \003(\004\"\235\002\n\021ProcedureWALEntry\022.\n\004",
+      "\007deleted\030\003 \003(\004\"\257\002\n\021ProcedureWALEntry\022.\n\004",
       "type\030\001 \002(\0162 .hbase.pb.ProcedureWALEntry." +
       "Type\022&\n\tprocedure\030\002 \003(\0132\023.hbase.pb.Proce" +
-      "dure\022\017\n\007proc_id\030\003 \001(\004\"\236\001\n\004Type\022\025\n\021PROCED" +
+      "dure\022\017\n\007proc_id\030\003 \001(\004\022\020\n\010child_id\030\004 \003(\004\"" +
-      "URE_WAL_EOF\020\001\022\026\n\022PROCEDURE_WAL_INIT\020\002\022\030\n" +
+      "\236\001\n\004Type\022\025\n\021PROCEDURE_WAL_EOF\020\001\022\026\n\022PROCE" +
-      "\024PROCEDURE_WAL_INSERT\020\003\022\030\n\024PROCEDURE_WAL" +
+      "DURE_WAL_INIT\020\002\022\030\n\024PROCEDURE_WAL_INSERT\020" +
-      "_UPDATE\020\004\022\030\n\024PROCEDURE_WAL_DELETE\020\005\022\031\n\025P" +
+      "\003\022\030\n\024PROCEDURE_WAL_UPDATE\020\004\022\030\n\024PROCEDURE" +
-      "ROCEDURE_WAL_COMPACT\020\006*p\n\016ProcedureState" +
+      "_WAL_DELETE\020\005\022\031\n\025PROCEDURE_WAL_COMPACT\020\006" +
-      "\022\020\n\014INITIALIZING\020\001\022\014\n\010RUNNABLE\020\002\022\013\n\007WAIT" +
+      "*p\n\016ProcedureState\022\020\n\014INITIALIZING\020\001\022\014\n\010" +
-      "ING\020\003\022\023\n\017WAITING_TIMEOUT\020\004\022\016\n\nROLLEDBACK" +
+      "RUNNABLE\020\002\022\013\n\007WAITING\020\003\022\023\n\017WAITING_TIMEO" +
-      "\020\005\022\014\n\010FINISHED\020\006BE\n*org.apache.hadoop.hb",
+      "UT\020\004\022\016\n\nROLLEDBACK\020\005\022\014\n\010FINISHED\020\006BE\n*or",
-      "ase.protobuf.generatedB\017ProcedureProtosH" +
+      "g.apache.hadoop.hbase.protobuf.generated" +
-      "\001\210\001\001\240\001\001"
+      "B\017ProcedureProtosH\001\210\001\001\240\001\001"
     };
     com.google.protobuf.Descriptors.FileDescriptor.InternalDescriptorAssigner assigner =
       new com.google.protobuf.Descriptors.FileDescriptor.InternalDescriptorAssigner() {
@@ -7421,7 +7584,7 @@ public final class ProcedureProtos {
           internal_static_hbase_pb_ProcedureWALEntry_fieldAccessorTable = new
             com.google.protobuf.GeneratedMessage.FieldAccessorTable(
               internal_static_hbase_pb_ProcedureWALEntry_descriptor,
-              new java.lang.String[] { "Type", "Procedure", "ProcId", });
+              new java.lang.String[] { "Type", "Procedure", "ProcId", "ChildId", });
           return null;
         }
       };

hbase-protocol/src/main/protobuf/Procedure.proto

@@ -116,4 +116,5 @@ message ProcedureWALEntry {
   required Type type = 1;
   repeated Procedure procedure = 2;
   optional uint64 proc_id = 3;
+  repeated uint64 child_id = 4;
 }