[SPARK-11823][SQL] Fix flaky JDBC cancellation test in HiveThriftBinaryServerSuite

This patch fixes a flaky "test jdbc cancel" test in HiveThriftBinaryServerSuite. This test is prone to a race-condition which causes it to block indefinitely with while waiting for an extremely slow query to complete, which caused many Jenkins builds to time out.

For more background, see my comments on #6207 (the PR which introduced this test).

Author: Josh Rosen <joshrosen@databricks.com>

Closes #10425 from JoshRosen/SPARK-11823.

sql/hive-thriftserver/src/test/scala/org/apache/spark/sql/hive/thriftserver/HiveThriftServer2Suites.scala

@@ -23,9 +23,8 @@ import java.sql.{Date, DriverManager, SQLException, Statement}
 
 import scala.collection.mutable
 import scala.collection.mutable.ArrayBuffer
-import scala.concurrent.ExecutionContext.Implicits.global
 import scala.concurrent.duration._
-import scala.concurrent.{Await, Promise, future}
+import scala.concurrent.{Await, ExecutionContext, Promise, future}
 import scala.io.Source
 import scala.util.{Random, Try}
 
@@ -43,7 +42,7 @@ import org.scalatest.BeforeAndAfterAll
 
 import org.apache.spark.sql.hive.HiveContext
 import org.apache.spark.sql.test.ProcessTestUtils.ProcessOutputCapturer
-import org.apache.spark.util.Utils
+import org.apache.spark.util.{ThreadUtils, Utils}
 import org.apache.spark.{Logging, SparkFunSuite}
 
 object TestData {
@@ -356,31 +355,54 @@ class HiveThriftBinaryServerSuite extends HiveThriftJdbcTest {
         s"LOAD DATA LOCAL INPATH '${TestData.smallKv}' OVERWRITE INTO TABLE test_map")
 
       queries.foreach(statement.execute)
-
-      val largeJoin = "SELECT COUNT(*) FROM test_map " +
-        List.fill(10)("join test_map").mkString(" ")
-      val f = future { Thread.sleep(100); statement.cancel(); }
-      val e = intercept[SQLException] {
-        statement.executeQuery(largeJoin)
+      implicit val ec = ExecutionContext.fromExecutorService(
+        ThreadUtils.newDaemonSingleThreadExecutor("test-jdbc-cancel"))
+      try {
+        // Start a very-long-running query that will take hours to finish, then cancel it in order
+        // to demonstrate that cancellation works.
+        val f = future {
+          statement.executeQuery(
+            "SELECT COUNT(*) FROM test_map " +
+            List.fill(10)("join test_map").mkString(" "))
+        }
+        // Note that this is slightly race-prone: if the cancel is issued before the statement
+        // begins executing then we'll fail with a timeout. As a result, this fixed delay is set
+        // slightly more conservatively than may be strictly necessary.
+        Thread.sleep(1000)
+        statement.cancel()
+        val e = intercept[SQLException] {
+          Await.result(f, 3.minute)
+        }
+        assert(e.getMessage.contains("cancelled"))
+
+        // Cancellation is a no-op if spark.sql.hive.thriftServer.async=false
+        statement.executeQuery("SET spark.sql.hive.thriftServer.async=false")
+        try {
+          val sf = future {
+            statement.executeQuery(
+              "SELECT COUNT(*) FROM test_map " +
+                List.fill(4)("join test_map").mkString(" ")
+            )
+          }
+          // Similarly, this is also slightly race-prone on fast machines where the query above
+          // might race and complete before we issue the cancel.
+          Thread.sleep(1000)
+          statement.cancel()
+          val rs1 = Await.result(sf, 3.minute)
+          rs1.next()
+          assert(rs1.getInt(1) === math.pow(5, 5))
+          rs1.close()
+
+          val rs2 = statement.executeQuery("SELECT COUNT(*) FROM test_map")
+          rs2.next()
+          assert(rs2.getInt(1) === 5)
+          rs2.close()
+        } finally {
+          statement.executeQuery("SET spark.sql.hive.thriftServer.async=true")
+        }
+      } finally {
+        ec.shutdownNow()
       }
-      assert(e.getMessage contains "cancelled")
-      Await.result(f, 3.minute)
-
-      // cancel is a noop
-      statement.executeQuery("SET spark.sql.hive.thriftServer.async=false")
-      val sf = future { Thread.sleep(100); statement.cancel(); }
-      val smallJoin = "SELECT COUNT(*) FROM test_map " +
-        List.fill(4)("join test_map").mkString(" ")
-      val rs1 = statement.executeQuery(smallJoin)
-      Await.result(sf, 3.minute)
-      rs1.next()
-      assert(rs1.getInt(1) === math.pow(5, 5))
-      rs1.close()
-
-      val rs2 = statement.executeQuery("SELECT COUNT(*) FROM test_map")
-      rs2.next()
-      assert(rs2.getInt(1) === 5)
-      rs2.close()
     }
   }
 
@@ -817,6 +839,7 @@ abstract class HiveThriftServer2Test extends SparkFunSuite with BeforeAndAfterAl
   }
 
   override protected def beforeAll(): Unit = {
+    super.beforeAll()
     // Chooses a random port between 10000 and 19999
     listeningPort = 10000 + Random.nextInt(10000)
     diagnosisBuffer.clear()
@@ -838,7 +861,11 @@ abstract class HiveThriftServer2Test extends SparkFunSuite with BeforeAndAfterAl
   }
 
   override protected def afterAll(): Unit = {
-    stopThriftServer()
-    logInfo("HiveThriftServer2 stopped")
+    try {
+      stopThriftServer()
+      logInfo("HiveThriftServer2 stopped")
+    } finally {
+      super.afterAll()
+    }
   }
 }