YARN-8715. Make allocation tags in the placement spec optional for node-attributes. Contributed by Weiwei Yang.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/util/constraint/PlacementConstraintParser.java

@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.yarn.util.constraint;
 
+import com.google.common.base.Strings;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.yarn.api.records.NodeAttributeOpCode;
@@ -589,6 +590,14 @@ public final class PlacementConstraintParser {
       this.num = number;
     }
 
+    public static SourceTags emptySourceTags() {
+      return new SourceTags("", 0);
+    }
+
+    public boolean isEmpty() {
+      return Strings.isNullOrEmpty(tag) && num == 0;
+    }
+
     public String getTag() {
       return this.tag;
     }
@@ -692,20 +701,47 @@ public final class PlacementConstraintParser {
       // foo=4,Pn
       String[] splitted = specStr.split(
           String.valueOf(EXPRESSION_VAL_DELIM), 2);
-      if (splitted.length != 2) {
+      final SourceTags st;
+      final String exprs;
+      if (splitted.length == 1) {
+        // source tags not specified
+        exprs = splitted[0];
+        st = SourceTags.emptySourceTags();
+      } else if (splitted.length == 2) {
+        exprs = splitted[1];
+        String tagAlloc = splitted[0];
+        st = SourceTags.parseFrom(tagAlloc);
+      } else {
         throw new PlacementConstraintParseException(
             "Unexpected placement constraint expression " + specStr);
       }
 
-      String tagAlloc = splitted[0];
-      SourceTags st = SourceTags.parseFrom(tagAlloc);
-      String exprs = splitted[1];
       AbstractConstraint constraint =
           PlacementConstraintParser.parseExpression(exprs);
 
       result.put(st, constraint.build());
     }
 
+    // Validation
+    Set<SourceTags> sourceTagSet = result.keySet();
+    if (sourceTagSet.stream()
+        .filter(sourceTags -> sourceTags.isEmpty())
+        .findAny()
+        .isPresent()) {
+      // Source tags, e.g foo=3, is optional for a node-attribute constraint,
+      // but when source tags is absent, the parser only accept single
+      // constraint expression to avoid ambiguous semantic. This is because
+      // DS AM is requesting number of containers per the number specified
+      // in the source tags, we do overwrite when there is no source tags
+      // with num_containers argument from commandline. If that is partially
+      // missed in the constraints, we don't know if it is ought to
+      // overwritten or not.
+      if (result.size() != 1) {
+        throw new PlacementConstraintParseException(
+            "Source allocation tags is required for a multi placement"
+                + " constraint expression.");
+      }
+    }
     return result;
   }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/test/java/org/apache/hadoop/yarn/api/resource/TestPlacementConstraintParser.java

@@ -501,5 +501,27 @@ public class TestPlacementConstraintParser {
     actualPc2 = valueIt.next();
     Assert.assertEquals(expectedPc1, actualPc1.getConstraintExpr());
     Assert.assertEquals(expectedPc2, actualPc2.getConstraintExpr());
+
+    // A single node attribute constraint w/o source tags
+    result = PlacementConstraintParser
+        .parsePlacementSpec("rm.yarn.io/foo=true");
+    Assert.assertEquals(1, result.size());
+    target = PlacementTargets.nodeAttribute("rm.yarn.io/foo", "true");
+    expectedPc1 = targetNodeAttribute("node", NodeAttributeOpCode.EQ, target);
+
+    SourceTags actualSourceTags = result.keySet().iterator().next();
+    Assert.assertTrue(actualSourceTags.isEmpty());
+    actualPc1 = result.values().iterator().next();
+    Assert.assertEquals(expectedPc1, actualPc1.getConstraintExpr());
+
+    // If source tags is not specified for a node-attribute constraint,
+    // then this expression must be single constraint expression.
+    try {
+      PlacementConstraintParser
+          .parsePlacementSpec("rm.yarn.io/foo=true:xyz=1,notin,node,xyz");
+      Assert.fail("Expected a failure!");
+    } catch (Exception e) {
+      Assert.assertTrue(e instanceof PlacementConstraintParseException);
+    }
   }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-applications/hadoop-yarn-applications-distributedshell/src/main/java/org/apache/hadoop/yarn/applications/distributedshell/ApplicationMaster.java

@@ -47,6 +47,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 import java.util.Arrays;
 import java.util.concurrent.atomic.AtomicLong;
 
+import com.google.common.base.Strings;
 import org.apache.commons.cli.CommandLine;
 import org.apache.commons.cli.GnuParser;
 import org.apache.commons.cli.HelpFormatter;
@@ -527,7 +528,9 @@ public class ApplicationMaster {
       LOG.info("Placement Spec received [{}]", decodedSpec);
 
       this.numTotalContainers = 0;
-      parsePlacementSpecs(decodedSpec);
+      int globalNumOfContainers = Integer
+          .parseInt(cliParser.getOptionValue("num_containers", "0"));
+      parsePlacementSpecs(decodedSpec, globalNumOfContainers);
       LOG.info("Total num containers requested [{}]", numTotalContainers);
 
       if (numTotalContainers == 0) {
@@ -698,11 +701,19 @@ public class ApplicationMaster {
     return true;
   }
 
-  private void parsePlacementSpecs(String decodedSpec) {
+  private void parsePlacementSpecs(String decodedSpec,
+      int globalNumOfContainers) {
     Map<String, PlacementSpec> pSpecs =
         PlacementSpec.parse(decodedSpec);
     this.placementSpecs = new HashMap<>();
     for (PlacementSpec pSpec : pSpecs.values()) {
+      // Use global num of containers when the spec doesn't specify
+      // source tags. This is allowed when using node-attribute constraints.
+      if (Strings.isNullOrEmpty(pSpec.sourceTag)
+          && pSpec.getNumContainers() == 0
+          && globalNumOfContainers > 0) {
+        pSpec.setNumContainers(globalNumOfContainers);
+      }
       this.numTotalContainers += pSpec.getNumContainers();
       this.placementSpecs.put(pSpec.sourceTag, pSpec);
     }
@@ -799,8 +810,9 @@ public class ApplicationMaster {
       placementConstraintMap = new HashMap<>();
       for (PlacementSpec spec : this.placementSpecs.values()) {
         if (spec.constraint != null) {
-          placementConstraintMap.put(
+          Set<String> allocationTags = Strings.isNullOrEmpty(spec.sourceTag) ?
-              Collections.singleton(spec.sourceTag), spec.constraint);
+              Collections.emptySet() : Collections.singleton(spec.sourceTag);
+          placementConstraintMap.put(allocationTags, spec.constraint);
         }
       }
     }