YARN-9258. Support to specify allocation tags without constraint in distributed shell CLI. Contributed by Prabhu Joseph.

(cherry picked from commit 6c4ab0312b9829f5cb3db0480406fe79f0125f5e)

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

@@ -255,7 +255,7 @@ public final class PlacementConstraintParser {
 
   /**
    * Tokenizer used to parse allocation tags expression, which should be
-   * in tag=numOfAllocations syntax.
+   * in tag(numOfAllocations) syntax.
    */
   public static class SourceTagsTokenizer implements ConstraintTokenizer {
 
@@ -264,22 +264,24 @@ public final class PlacementConstraintParser {
     private Iterator<String> iterator;
     public SourceTagsTokenizer(String expr) {
       this.expression = expr;
-      st = new StringTokenizer(expr, String.valueOf(KV_SPLIT_DELIM));
+      st = new StringTokenizer(expr, String.valueOf(BRACKET_START));
     }
 
     @Override
     public void validate() throws PlacementConstraintParseException {
       ArrayList<String> parsedValues = new ArrayList<>();
-      if (st.countTokens() != 2) {
+      if (st.countTokens() != 2  || !this.expression.
+          endsWith(String.valueOf(BRACKET_END))) {
         throw new PlacementConstraintParseException(
             "Expecting source allocation tag to be specified"
-                + " sourceTag=numOfAllocations syntax,"
-                + " but met " + expression);
+            + " sourceTag(numOfAllocations) syntax,"
+            + " but met " + expression);
       }
 
       String sourceTag = st.nextToken();
       parsedValues.add(sourceTag);
-      String num = st.nextToken();
+      String str = st.nextToken();
+      String num = str.substring(0, str.length() - 1);
       try {
         Integer.parseInt(num);
         parsedValues.add(num);
@@ -630,7 +632,7 @@ public final class PlacementConstraintParser {
     }
 
     /**
-     * Parses source tags from expression "sourceTags=numOfAllocations".
+     * Parses source tags from expression "sourceTags(numOfAllocations)".
      * @param expr
      * @return source tags, see {@link SourceTags}
      * @throws PlacementConstraintParseException
@@ -690,12 +692,14 @@ public final class PlacementConstraintParser {
    * is a composite expression which is composed by multiple sub constraint
    * expressions delimited by ":". With following syntax:
    *
-   * <p>Tag1=N1,P1:Tag2=N2,P2:...:TagN=Nn,Pn</p>
+   * <p>Tag1(N1),P1:Tag2(N2),P2:...:TagN(Nn),Pn</p>
    *
-   * where <b>TagN=Nn</b> is a key value pair to determine the source
+   * where <b>TagN(Nn)</b> is a key value pair to determine the source
    * allocation tag and the number of allocations, such as:
    *
-   * <p>foo=3</p>
+   * <p>foo(3)</p>
+   *
+   * Optional when using NodeAttribute Constraint.
    *
    * and where <b>Pn</b> can be any form of a valid constraint expression,
    * such as:
@@ -705,6 +709,13 @@ public final class PlacementConstraintParser {
    *   <li>notin,node,foo,bar,1,2</li>
    *   <li>and(notin,node,foo:notin,node,bar)</li>
    * </ul>
+   *
+   * and NodeAttribute Constraint such as
+   *
+   * <ul>
+   *   <li>yarn.rm.io/foo=true</li>
+   *   <li>java=1.7,1.8</li>
+   * </ul>
    * @param expression expression string.
    * @return a map of source tags to placement constraint mapping.
    * @throws PlacementConstraintParseException
@@ -719,30 +730,35 @@ public final class PlacementConstraintParser {
     tokenizer.validate();
     while (tokenizer.hasMoreElements()) {
       String specStr = tokenizer.nextElement();
-      // each spec starts with sourceAllocationTag=numOfContainers and
+      // each spec starts with sourceAllocationTag(numOfContainers) and
       // followed by a constraint expression.
-      // foo=4,Pn
-      String[] splitted = specStr.split(
-          String.valueOf(EXPRESSION_VAL_DELIM), 2);
+      // foo(4),Pn
       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);
+      PlacementConstraint constraint;
+      String delimiter = new String(new char[]{'[', BRACKET_END, ']',
+          EXPRESSION_VAL_DELIM});
+      String[] splitted = specStr.split(delimiter, 2);
+      if (splitted.length == 2) {
+        st = SourceTags.parseFrom(splitted[0] + String.valueOf(BRACKET_END));
+        constraint = PlacementConstraintParser.parseExpression(splitted[1]).
+            build();
+      } else if (splitted.length == 1) {
+        // Either Node Attribute Constraint or Source Allocation Tag alone
+        NodeConstraintParser np = new NodeConstraintParser(specStr);
+        Optional<AbstractConstraint> constraintOptional =
+            Optional.ofNullable(np.tryParse());
+        if (constraintOptional.isPresent()) {
+          st = SourceTags.emptySourceTags();
+          constraint = constraintOptional.get().build();
+        } else {
+          st = SourceTags.parseFrom(specStr);
+          constraint = null;
+        }
       } else {
         throw new PlacementConstraintParseException(
             "Unexpected placement constraint expression " + specStr);
       }
-
-      AbstractConstraint constraint =
-          PlacementConstraintParser.parseExpression(exprs);
-
-      result.put(st, constraint.build());
+      result.put(st, constraint);
     }
 
     // Validation
@@ -751,7 +767,7 @@ public final class PlacementConstraintParser {
         .filter(sourceTags -> sourceTags.isEmpty())
         .findAny()
         .isPresent()) {
-      // Source tags, e.g foo=3, is optional for a node-attribute constraint,
+      // 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

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

@@ -22,6 +22,7 @@ import com.google.common.collect.Sets;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Set;
+import java.util.TreeSet;
 
 import org.apache.hadoop.yarn.api.records.NodeAttributeOpCode;
 import org.apache.hadoop.yarn.api.resource.PlacementConstraint.AbstractConstraint;
@@ -274,15 +275,15 @@ public class TestPlacementConstraintParser {
     TokenizerTester mp;
 
     ct = new MultipleConstraintsTokenizer(
-        "foo=1,A1,A2,A3:bar=2,B1,B2:moo=3,C1,C2");
+        "foo(1),A1,A2,A3:bar(2),B1,B2:moo(3),C1,C2");
     mp = new TokenizerTester(ct,
-        "foo=1,A1,A2,A3", "bar=2,B1,B2", "moo=3,C1,C2");
+        "foo(1),A1,A2,A3", "bar(2),B1,B2", "moo(3),C1,C2");
     mp.verify();
 
     ct = new MultipleConstraintsTokenizer(
-        "foo=1,AND(A2:A3):bar=2,OR(B1:AND(B2:B3)):moo=3,C1,C2");
+        "foo(1),AND(A2:A3):bar(2),OR(B1:AND(B2:B3)):moo(3),C1,C2");
     mp = new TokenizerTester(ct,
-        "foo=1,AND(A2:A3)", "bar=2,OR(B1:AND(B2:B3))", "moo=3,C1,C2");
+        "foo(1),AND(A2:A3)", "bar(2),OR(B1:AND(B2:B3))", "moo(3),C1,C2");
     mp.verify();
 
     ct = new MultipleConstraintsTokenizer("A:B:C");
@@ -301,12 +302,12 @@ public class TestPlacementConstraintParser {
     mp = new TokenizerTester(ct, "A", "AND(B:OR(C:D))", "E");
     mp.verify();
 
-    st = new SourceTagsTokenizer("A=4");
+    st = new SourceTagsTokenizer("A(4)");
     mp = new TokenizerTester(st, "A", "4");
     mp.verify();
 
     try {
-      st = new SourceTagsTokenizer("A=B");
+      st = new SourceTagsTokenizer("A(B)");
       mp = new TokenizerTester(st, "A", "B");
       mp.verify();
       Assert.fail("Expecting a parsing failure");
@@ -348,9 +349,20 @@ public class TestPlacementConstraintParser {
     PlacementConstraint actualPc1, actualPc2;
     SourceTags tag1, tag2;
 
+    // Only Source Tag without constraint
+    result = PlacementConstraintParser
+        .parsePlacementSpec("foo(3)");
+    Assert.assertEquals(1, result.size());
+    tag1 = result.keySet().iterator().next();
+    Assert.assertEquals("foo", tag1.getTag());
+    Assert.assertEquals(3, tag1.getNumOfAllocations());
+    expectedPc1 = null;
+    actualPc1 = result.values().iterator().next();
+    Assert.assertEquals(expectedPc1, actualPc1);
+
     // A single anti-affinity constraint
     result = PlacementConstraintParser
-        .parsePlacementSpec("foo=3,notin,node,foo");
+        .parsePlacementSpec("foo(3),notin,node,foo");
     Assert.assertEquals(1, result.size());
     tag1 = result.keySet().iterator().next();
     Assert.assertEquals("foo", tag1.getTag());
@@ -361,7 +373,7 @@ public class TestPlacementConstraintParser {
 
     // Upper case
     result = PlacementConstraintParser
-        .parsePlacementSpec("foo=3,NOTIN,NODE,foo");
+        .parsePlacementSpec("foo(3),NOTIN,NODE,foo");
     Assert.assertEquals(1, result.size());
     tag1 = result.keySet().iterator().next();
     Assert.assertEquals("foo", tag1.getTag());
@@ -372,7 +384,7 @@ public class TestPlacementConstraintParser {
 
     // A single cardinality constraint
     result = PlacementConstraintParser
-        .parsePlacementSpec("foo=10,cardinality,node,foo,bar,0,100");
+        .parsePlacementSpec("foo(10),cardinality,node,foo,bar,0,100");
     Assert.assertEquals(1, result.size());
     tag1 = result.keySet().iterator().next();
     Assert.assertEquals("foo", tag1.getTag());
@@ -386,7 +398,7 @@ public class TestPlacementConstraintParser {
 
     // Two constraint expressions
     result = PlacementConstraintParser
-        .parsePlacementSpec("foo=3,notin,node,foo:bar=2,in,node,foo");
+        .parsePlacementSpec("foo(3),notin,node,foo:bar(2),in,node,foo");
     Assert.assertEquals(2, result.size());
     Iterator<SourceTags> keyIt = result.keySet().iterator();
     tag1 = keyIt.next();
@@ -403,7 +415,7 @@ public class TestPlacementConstraintParser {
 
     // And constraint
     result = PlacementConstraintParser
-        .parsePlacementSpec("foo=1000,and(notin,node,bar:in,node,foo)");
+        .parsePlacementSpec("foo(1000),and(notin,node,bar:in,node,foo)");
     Assert.assertEquals(1, result.size());
     keyIt = result.keySet().iterator();
     tag1 = keyIt.next();
@@ -416,8 +428,8 @@ public class TestPlacementConstraintParser {
 
     // Multiple constraints with nested forms.
     result = PlacementConstraintParser.parsePlacementSpec(
-            "foo=1000,and(notin,node,bar:or(in,node,foo:in,node,moo))"
-                + ":bar=200,notin,node,foo");
+            "foo(1000),and(notin,node,bar:or(in,node,foo:in,node,moo))"
+                + ":bar(200),notin,node,foo");
     Assert.assertEquals(2, result.size());
     keyIt = result.keySet().iterator();
     tag1 = keyIt.next();
@@ -436,6 +448,17 @@ public class TestPlacementConstraintParser {
     Assert.assertEquals(actualPc1, expectedPc1);
     expectedPc2 = targetNotIn("node", allocationTag("foo")).build();
     Assert.assertEquals(expectedPc2, actualPc2);
+
+    // Failure Cases
+    String[] invalidSpecs = {"foo(3", "foo),bar", "foobar", "),java=1.7,1.8"};
+    for (String spec : invalidSpecs) {
+      try {
+        result = PlacementConstraintParser.parsePlacementSpec(spec);
+        Assert.fail("Expected a failure!");
+      } catch (Exception e) {
+        Assert.assertTrue(e instanceof PlacementConstraintParseException);
+      }
+    }
   }
 
   // We verify the toString result by parsing it again
@@ -466,7 +489,7 @@ public class TestPlacementConstraintParser {
 
     // A single node attribute constraint
     result = PlacementConstraintParser
-        .parsePlacementSpec("xyz=4,rm.yarn.io/foo=true");
+        .parsePlacementSpec("xyz(4),rm.yarn.io/foo=true");
     Assert.assertEquals(1, result.size());
     TargetExpression target = PlacementTargets
         .nodeAttribute("rm.yarn.io/foo", "true");
@@ -477,7 +500,7 @@ public class TestPlacementConstraintParser {
 
     // A single node attribute constraint
     result = PlacementConstraintParser
-        .parsePlacementSpec("xyz=3,rm.yarn.io/foo!=abc");
+        .parsePlacementSpec("xyz(3),rm.yarn.io/foo!=abc");
     Assert.assertEquals(1, result.size());
     target = PlacementTargets
         .nodeAttribute("rm.yarn.io/foo", "abc");
@@ -492,7 +515,7 @@ public class TestPlacementConstraintParser {
     // A single node attribute constraint
     result = PlacementConstraintParser
         .parsePlacementSpec(
-            "xyz=1,rm.yarn.io/foo!=abc:zxy=1,rm.yarn.io/bar=true");
+            "xyz(1),rm.yarn.io/foo!=abc:zxy(1),rm.yarn.io/bar=true");
     Assert.assertEquals(2, result.size());
     target = PlacementTargets
         .nodeAttribute("rm.yarn.io/foo", "abc");
@@ -519,11 +542,27 @@ public class TestPlacementConstraintParser {
     actualPc1 = result.values().iterator().next();
     Assert.assertEquals(expectedPc1, actualPc1.getConstraintExpr());
 
+    // Node Attribute Constraint With Multiple Values
+    result = PlacementConstraintParser
+        .parsePlacementSpec("java=1.7,1.8");
+    Assert.assertEquals(1, result.size());
+
+    Set<String> constraintEntities = new TreeSet<>();
+    constraintEntities.add("1.7");
+    constraintEntities.add("1.8");
+    target = PlacementConstraints.PlacementTargets.nodeAttribute("java",
+        constraintEntities.toArray(new String[constraintEntities.size()]));
+    expectedPc1 = targetNodeAttribute("node", NodeAttributeOpCode.EQ, target);
+    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");
+          .parsePlacementSpec("rm.yarn.io/foo=true:xyz(1),notin,node,xyz");
       Assert.fail("Expected a failure!");
     } catch (Exception e) {
       Assert.assertTrue(e instanceof PlacementConstraintParseException);
@@ -537,7 +576,7 @@ public class TestPlacementConstraintParser {
 
     // Constraint with Two Different NameSpaces
     result = PlacementConstraintParser
-        .parsePlacementSpec("foo=2,notin,node,not-self/bar,all/moo");
+        .parsePlacementSpec("foo(2),notin,node,not-self/bar,all/moo");
     Assert.assertEquals(1, result.size());
     Set<TargetExpression> expectedTargetExpressions = Sets.newHashSet(
         PlacementTargets.allocationTagWithNamespace("not-self", "bar"),
@@ -552,7 +591,7 @@ public class TestPlacementConstraintParser {
 
     // Constraint With Default NameSpace SELF
     result = PlacementConstraintParser
-        .parsePlacementSpec("foo=2,notin,node,moo");
+        .parsePlacementSpec("foo(2),notin,node,moo");
     Assert.assertEquals(1, result.size());
     TargetExpression expectedTargetExpression = PlacementTargets.
         allocationTagWithNamespace("self", "moo");
@@ -567,7 +606,7 @@ public class TestPlacementConstraintParser {
     boolean caughtException = false;
     try {
       result = PlacementConstraintParser
-          .parsePlacementSpec("foo=2,notin,node,bar/moo");
+          .parsePlacementSpec("foo(2),notin,node,bar/moo");
     } catch(PlacementConstraintParseException e) {
       caughtException = true;
     }

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

@@ -96,8 +96,12 @@ public class PlacementSpec {
           parsed.entrySet()) {
         LOG.info("Parsed source tag: {}, number of allocations: {}",
             entry.getKey().getTag(), entry.getKey().getNumOfAllocations());
-        LOG.info("Parsed constraint: {}", entry.getValue()
-            .getConstraintExpr().getClass().getSimpleName());
+        if (entry.getValue() != null) {
+          LOG.info("Parsed constraint: {}", entry.getValue()
+              .getConstraintExpr().getClass().getSimpleName());
+        } else {
+          LOG.info("Parsed constraint Empty");
+        }
         pSpecs.put(entry.getKey().getTag(), new PlacementSpec(
             entry.getKey().getTag(),
             entry.getKey().getNumOfAllocations(),

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-applications/hadoop-yarn-applications-distributedshell/src/test/java/org/apache/hadoop/yarn/applications/distributedshell/TestDSWithMultipleNodeManager.java

@@ -156,7 +156,7 @@ public class TestDSWithMultipleNodeManager {
         "--shell_command",
         distShellTest.getSleepCommand(15),
         "--placement_spec",
-        "zk=1,NOTIN,NODE,zk:spark=1,NOTIN,NODE,zk"
+        "zk(1),NOTIN,NODE,zk:spark(1),NOTIN,NODE,zk"
     };
     LOG.info("Initializing DS Client");
     final Client client =
@@ -202,7 +202,7 @@ public class TestDSWithMultipleNodeManager {
         "--shell_command",
         distShellTest.getSleepCommand(30),
         "--placement_spec",
-        "bar=1,notin,node,bar"
+        "bar(1),notin,node,bar"
     };
     final Client clientA =
         new Client(new Configuration(distShellTest.yarnCluster.getConfig()));
@@ -275,7 +275,7 @@ public class TestDSWithMultipleNodeManager {
         "--shell_command",
         Shell.WINDOWS ? "dir" : "ls",
         "--placement_spec",
-        "foo=3,notin,node,all/bar"
+        "foo(3),notin,node,all/bar"
     };
     final Client clientB = new Client(new Configuration(distShellTest.
         yarnCluster.getConfig()));

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/PlacementConstraints.md.vm

@@ -65,26 +65,29 @@ $ yarn org.apache.hadoop.yarn.applications.distributedshell.Client -jar share/ha
 where **PlacementSpec** is of the form:
 
 ```
-PlacementSpec         => "" | KeyVal;PlacementSpec
-KeyVal                => SourceTag=ConstraintExpr
-SourceTag             => String
-ConstraintExpr        => NumContainers | NumContainers, Constraint
-Constraint            => SingleConstraint | CompositeConstraint
-SingleConstraint      => "IN",Scope,TargetTag | "NOTIN",Scope,TargetTag | "CARDINALITY",Scope,TargetTag,MinCard,MaxCard
-CompositeConstraint   => AND(ConstraintList) | OR(ConstraintList)
-ConstraintList        => Constraint | Constraint:ConstraintList
-NumContainers         => int
-Scope                 => "NODE" | "RACK"
-TargetTag             => String
-MinCard               => int
-MaxCard               => int
+PlacementSpec               => "" | PlacementExpr;PlacementSpec
+PlacementExpr               => SourceTag,ConstraintExpr
+SourceTag                   => String(NumContainers)
+ConstraintExpr              => SingleConstraint | CompositeConstraint
+SingleConstraint            => "IN",Scope,TargetTag | "NOTIN",Scope,TargetTag | "CARDINALITY",Scope,TargetTag,MinCard,MaxCard | NodeAttributeConstraintExpr
+NodeAttributeConstraintExpr => NodeAttributeName=Value, NodeAttributeName!=Value
+CompositeConstraint         => AND(ConstraintList) | OR(ConstraintList)
+ConstraintList              => Constraint | Constraint:ConstraintList
+NumContainers               => int
+Scope                       => "NODE" | "RACK"
+TargetTag                   => String
+MinCard                     => int
+MaxCard                     => int
 ```
 
-Note that when the `-placement_spec` argument is specified in the distributed shell command, the `-num-containers` argument should not be used. In case `-num-containers` argument is used in conjunction with `-placement-spec`, the former is ignored. This is because in PlacementSpec, we determine the number of containers per tag, making the `-num-containers` redundant and possibly conflicting. Moreover, if `-placement_spec` is used, all containers will be requested with GUARANTEED execution type.
+Note:
+
+* When the `-placement_spec` argument is specified (except NodeAttributeConstraintExpr) in the distributed shell command, the `-num-containers` argument should not be used. In case `-num-containers` argument is used in conjunction with `-placement-spec`, the former is ignored. This is because in PlacementSpec, we determine the number of containers per tag, making the `-num-containers` redundant and possibly conflicting. Moreover, if `-placement_spec` is used, all containers will be requested with GUARANTEED execution type.
+* When the `NodeAttributeConstraintExpr` is specified, `SourceTag(NumContainers)` is optional and the value of `-num-containers` will be considered for the number of containers to request.
 
 An example of PlacementSpec is the following:
 ```
-zk=3,NOTIN,NODE,zk:hbase=5,IN,RACK,zk:spark=7,CARDINALITY,NODE,hbase,1,3
+zk(3),NOTIN,NODE,zk:hbase(5),IN,RACK,zk:spark(7),CARDINALITY,NODE,hbase,1,3
 ```
 The above encodes three constraints:
 
@@ -94,7 +97,7 @@ The above encodes three constraints:
 
 Another example below demonstrates a composite form of constraint:
 ```
-zk=5,AND(IN,RACK,hbase:NOTIN,NODE,zk)
+zk(5),AND(IN,RACK,hbase:NOTIN,NODE,zk)
 ```
 The above constraint uses the conjunction operator `AND` to combine two constraints. The AND constraint is satisfied when both its children constraints are satisfied. The specific PlacementSpec requests to place 5 "zk" containers in a rack where at least one "hbase" container is running, and on a node that no "zk" container is running.
 Similarly, an `OR` operator can be used to define a constraint that is satisfied when at least one of its children constraints is satisfied.
@@ -130,7 +133,7 @@ To attach an allocation tag namespace `ns` to a target tag `targetTag`, we use t
 
 The example constraints used above could be extended with namespaces as follows:
 ```
-zk=3,NOTIN,NODE,not-self/zk:hbase=5,IN,RACK,all/zk:spark=7,CARDINALITY,NODE,app-id/appID_0023/hbase,1,3
+zk(3),NOTIN,NODE,not-self/zk:hbase(5),IN,RACK,all/zk:spark(7),CARDINALITY,NODE,app-id/appID_0023/hbase,1,3
 ```
 The semantics of these constraints are the following:
 
@@ -175,4 +178,4 @@ Applications have to specify the containers for which each constraint will be en
 
 When using the `placement-processor` handler (see [Enabling placement constraints](#Enabling_placement_constraints)), this constraint mapping is specified within the `RegisterApplicationMasterRequest`.
 
-When using the `scheduler` handler, the constraints can also be added at each `SchedulingRequest` object. Each such constraint is valid for the tag of that scheduling request. In case constraints are specified both at the `RegisterApplicationMasterRequest` and the scheduling requests, the latter override the former.
+When using the `scheduler` handler, the constraints can also be added at each `SchedulingRequest` object. Each such constraint is valid for the tag of that scheduling request. In case constraints are specified both at the `RegisterApplicationMasterRequest` and the scheduling requests, the latter override the former.