ATLAS-471 Atlas Server could run out of memory due to Scala memory leak(yhemanth via sumasai)

repository/src/main/java/org/apache/atlas/discovery/graph/GraphBackedDiscoveryService.java

@@ -128,8 +128,7 @@ public class GraphBackedDiscoveryService implements DiscoveryService {
     public GremlinQueryResult evaluate(String dslQuery) throws DiscoveryException {
         LOG.info("Executing dsl query={}", dslQuery);
         try {
-            QueryParser queryParser = new QueryParser();
-            Either<Parsers.NoSuccess, Expressions.Expression> either = queryParser.apply(dslQuery);
+            Either<Parsers.NoSuccess, Expressions.Expression> either = QueryParser.apply(dslQuery);
             if (either.isRight()) {
                 Expressions.Expression expression = either.right().get();
                 return evaluate(expression);

repository/src/main/scala/org/apache/atlas/query/QueryParser.scala

@@ -107,7 +107,7 @@ trait ExpressionUtils {
     }
 }
 
-class QueryParser extends StandardTokenParsers with QueryKeywords with ExpressionUtils with PackratParsers {
+object QueryParser extends StandardTokenParsers with QueryKeywords with ExpressionUtils with PackratParsers {
 
     import scala.language.higherKinds
 
@@ -119,7 +119,7 @@ class QueryParser extends StandardTokenParsers with QueryKeywords with Expressio
 
     override val lexical = new QueryLexer(queryreservedWords, querydelims)
 
-    def apply(input: String): Either[NoSuccess, Expression] = {
+    def apply(input: String): Either[NoSuccess, Expression] = synchronized {
         phrase(queryWithPath)(new lexical.Scanner(input)) match {
             case Success(r, x) => Right(r)
             case f@Failure(m, x) => Left(f)

repository/src/test/scala/org/apache/atlas/query/GremlinTest.scala

@@ -899,7 +899,7 @@ class GremlinTest extends BaseGremlinTest {
   }
 
   @Test def testArrayComparision {
-    val p = new QueryParser
+    val p = QueryParser
     val e = p("Partition as p where values = ['2015-01-01']," +
       " table where name = 'sales_fact_daily_mv'," +
       " db where name = 'Reporting' and clusterName = 'test' select p").right.get
@@ -937,7 +937,7 @@ class GremlinTest extends BaseGremlinTest {
   }
 
   @Test def testArrayComparisionWithSelectOnArray {
-    val p = new QueryParser
+    val p = QueryParser
     val e = p("Partition as p where values = ['2015-01-01']," +
       " table where name = 'sales_fact_daily_mv'," +
       " db where name = 'Reporting' and clusterName = 'test' select p.values").right.get
@@ -976,7 +976,7 @@ class GremlinTest extends BaseGremlinTest {
   }
 
   @Test def testArrayInWhereClause {
-    val p = new QueryParser
+    val p = QueryParser
     val e = p("Partition as p where values = ['2015-01-01']").right.get
     val r = QueryProcessor.evaluate(e, g, gp)
     validateJson(r, """{
@@ -1045,13 +1045,13 @@ class GremlinTest extends BaseGremlinTest {
 
   @Test(expectedExceptions =  Array(classOf[ExpressionException]))
   def testNegativeInvalidType {
-    val p = new QueryParser
+    val p = QueryParser
     val e = p("from blah").right.get
     QueryProcessor.evaluate(e, g, gp)
   }
 
   @Test def testJoinAndSelect5 {
-    val p = new QueryParser
+    val p = QueryParser
     val e = p("Table as t where name = 'sales_fact' db where name = 'Sales' and owner = 'John ETL' select t").right.get
     val r = QueryProcessor.evaluate(e, g, gp)
     validateJson(r)

repository/src/test/scala/org/apache/atlas/query/GremlinTest2.scala

@@ -89,7 +89,7 @@ class GremlinTest2 extends BaseGremlinTest {
   }
 
   @Test def testLineageAllSelectWithPathFromParser {
-    val p = new QueryParser
+    val p = QueryParser
     val e = p("Table as src loop (LoadProcess outputTable) as dest " +
       "select src.name as srcTable, dest.name as destTable withPath").right.get
     //Table as src loop (LoadProcess where LoadProcess.outputTable) as dest select src.name as srcTable, dest.name as destTable withPath
@@ -98,7 +98,7 @@ class GremlinTest2 extends BaseGremlinTest {
   }
 
   @Test def testLineageAllSelectWithPathFromParser2 {
-    val p = new QueryParser
+    val p = QueryParser
 
     val e = p("Table as src loop (`LoadProcess->outputTable` inputTables) as dest " +
       "select src.name as srcTable, dest.name as destTable withPath").right.get

repository/src/test/scala/org/apache/atlas/query/LexerTest.scala

@@ -25,8 +25,8 @@ import scala.util.parsing.input.CharArrayReader
 
 class LexerTest {
 
-    def scan(p: QueryParser, str: String): p.lexical.ParseResult[_] = {
-        val l = p.lexical
+    def scan(str: String): QueryParser.lexical.ParseResult[_] = {
+        val l = QueryParser.lexical
         var s: l.Input = new CharArrayReader(str.toCharArray)
         var r = (l.whitespace.? ~ l.token)(s)
         s = r.next
@@ -37,12 +37,11 @@ class LexerTest {
                 r = (l.whitespace.? ~ l.token)(s)
             }
         }
-        r.asInstanceOf[p.lexical.ParseResult[_]]
+        r.asInstanceOf[QueryParser.lexical.ParseResult[_]]
     }
 
     @Test def testSimple {
-        val p = new QueryParser
-        val r = scan(p, """DB where db1.name""")
+        val r = scan("""DB where db1.name""")
         Assert.assertTrue(r.successful)
 
     }

repository/src/test/scala/org/apache/atlas/query/ParserTest.scala

@@ -31,74 +31,61 @@ class ParserTest extends BaseTest {
     }
 
     @Test def testFrom: Unit = {
-        val p = new QueryParser
-        println(p("from DB").right.get.toString)
+        println(QueryParser.apply("from DB").right.get.toString)
     }
 
     @Test def testFrom2: Unit = {
-        val p = new QueryParser
-        println(p("DB").right.get.toString)
+        println(QueryParser.apply("DB").right.get.toString)
     }
 
     @Test def testJoin1: Unit = {
-        val p = new QueryParser
-        println(p("DB, Table").right.get.toString)
+        println(QueryParser.apply("DB, Table").right.get.toString)
     }
 
     @Test def testWhere1: Unit = {
-        val p = new QueryParser
-        println(p("DB as db1 Table where db1.name ").right.get.toString)
+        println(QueryParser.apply("DB as db1 Table where db1.name ").right.get.toString)
     }
 
     @Test def testWhere2: Unit = {
-        val p = new QueryParser
-        println(p("DB name = \"Reporting\"").right.get.toString)
+        println(QueryParser.apply("DB name = \"Reporting\"").right.get.toString)
     }
 
   @Test def testIsTrait: Unit = {
-    val p = new QueryParser
-    println(p("Table isa Dimension").right.get.toString)
-    println(p("Table is Dimension").right.get.toString)
+    println(QueryParser.apply("Table isa Dimension").right.get.toString)
+    println(QueryParser.apply("Table is Dimension").right.get.toString)
   }
 
     @Test def test4: Unit = {
-        val p = new QueryParser
-        println(p("DB where (name = \"Reporting\") select name as _col_0, (createTime + 1) as _col_1").right.get.toString)
+        println(QueryParser.apply("DB where (name = \"Reporting\") select name as _col_0, (createTime + 1) as _col_1").right.get.toString)
     }
 
     @Test def testJoin2: Unit = {
-        val p = new QueryParser
-        println(p("DB as db1 where (createTime + 1) > 0 and (db1.name = \"Reporting\") or DB has owner Table as tab " +
+        println(QueryParser.apply("DB as db1 where (createTime + 1) > 0 and (db1.name = \"Reporting\") or DB has owner Table as tab " +
             " select db1.name as dbName, tab.name as tabName").right.get.toString)
     }
 
     @Test def testLoop: Unit = {
-        val p = new QueryParser
-        println(p("Table loop (LoadProcess outputTable)").right.get.toString)
+        println(QueryParser.apply("Table loop (LoadProcess outputTable)").right.get.toString)
     }
 
   @Test def testNegInvalidateType: Unit = {
-    val p = new QueryParser
-    val x = p("from blah")
-    println(p("from blah").left)
+    val x = QueryParser.apply("from blah")
+    println(QueryParser.apply("from blah").left)
   }
 
     @Test def testPath1: Unit = {
-      val p = new QueryParser
-      println(p("Table loop (LoadProcess outputTable) withPath").right.get.toString)
+      println(QueryParser.apply("Table loop (LoadProcess outputTable) withPath").right.get.toString)
     }
 
     @Test def testPath2: Unit = {
-      val p = new QueryParser
-      println(p(
+      println(QueryParser.apply(
         "Table as src loop (LoadProcess outputTable) as dest " +
           "select src.name as srcTable, dest.name as destTable withPath").right.get.toString
       )
     }
 
   @Test def testList: Unit = {
-    val p = new QueryParser
-    println(p(
+    println(QueryParser.apply(
       "Partition as p where values = ['2015-01-01']," +
         " table where name = 'tableoq8ty'," +
         " db where name = 'default' and clusterName = 'test'").right.get.toString