[KYUUBI #659] Add UDF engine_name

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### _Why are the changes needed?_
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Add UDF engine_name to show the runtime information about execution engine

### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible

- [ ] Add screenshots for manual tests if appropriate

- [ ] [Run test](https://kyuubi.readthedocs.io/en/latest/tools/testing.html#running-tests) locally before make a pull request

Closes #747 from zhaomin1423/udf.

Closes #659

8c3b3c1 [Min Zhao] Merge branch 'master' into udf
f184a66 [Min Zhao] Merge branch 'master' into udf
9ea0c19 [Min Zhao] get appName from driver side
09f0752 [Min Zhao] get conf by SparkEnv.get.conf in the engine_name udf
6c00078 [Min Zhao] update the description of the engine_name udf
63ef276 [Min Zhao] update class to org.apache.kyuubi.engine.spark.udf.KyuubiDefinedFunctionSuite in functions.md
db02884 [Min Zhao] [KYUUBI #659] Add UDF engine_name

Lead-authored-by: Min Zhao <zhaomin1423@163.com>
Co-authored-by: Min Zhao <49054376+zhaomin1423@users.noreply.github.com>
Signed-off-by: Cheng Pan <chengpan@apache.org>
(cherry picked from commit 8bab5b8)
Signed-off-by: Cheng Pan <chengpan@apache.org>

docs/sql/functions.md

@@ -30,5 +30,6 @@ Kyuubi provides several auxiliary SQL functions as supplement to Spark's [Built-
 Name | Description | Return Type | Since
 --- | --- | --- | ---
 kyuubi_version | Return the version of Kyuubi Server | string | 1.3.0
+engine_name | Return the spark application name for the associated query engine | string | 1.3.0
 system_user | Return the system user name for the associated query engine | string | 1.3.0
 

externals/kyuubi-spark-sql-engine/src/main/scala/org/apache/kyuubi/engine/spark/udf/KDFRegistry.scala

@@ -29,13 +29,23 @@ object KDFRegistry {
 
   val registeredFunctions = new ArrayBuffer[KyuubiDefinedFunction]()
 
+  val appName = SparkSession.active.sparkContext.appName
+
   val kyuubi_version: KyuubiDefinedFunction = create(
     "kyuubi_version",
     udf(() => KYUUBI_VERSION).asNonNullable(),
     "Return the version of Kyuubi Server",
     "string",
     "1.3.0")
 
+  val engine_name: KyuubiDefinedFunction = create(
+    "engine_name",
+    udf(() => appName).asNonNullable(),
+    "Return the spark application name for the associated query engine",
+    "string",
+    "1.3.0"
+  )
+
   val system_user: KyuubiDefinedFunction = create(
     "system_user",
     udf(() => System.getProperty("user.name")).asNonNullable(),

externals/kyuubi-spark-sql-engine/src/test/scala/org/apache/kyuubi/engine/spark/udf/KyuubiDefinedFunctionSuite.scala

@@ -86,7 +86,6 @@ class KyuubiDefinedFunctionSuite extends KyuubiFunSuite {
     KDFRegistry.registeredFunctions.foreach { func =>
       newOutput += s"${func.name} | ${func.description} | ${func.returnType} | ${func.since}"
     }
-
     newOutput += ""
     TestUtils.verifyOutput(markdown, newOutput, getClass.getCanonicalName)
   }

kyuubi-common/src/test/scala/org/apache/kyuubi/operation/JDBCTests.scala

@@ -21,6 +21,7 @@ import java.sql.{Date, SQLException, SQLTimeoutException, Timestamp}
 
 import scala.collection.JavaConverters._
 
+import org.apache.commons.lang3.StringUtils
 import org.apache.hive.service.rpc.thrift.{TExecuteStatementReq, TFetchResultsReq, TOpenSessionReq, TStatusCode}
 
 import org.apache.kyuubi.KYUUBI_VERSION
@@ -362,6 +363,14 @@ trait JDBCTests extends BasicJDBCTests {
     }
   }
 
+  test("kyuubi defined function - engine_name") {
+    withJdbcStatement() { statement =>
+      val rs = statement.executeQuery("SELECT engine_name()")
+      assert(rs.next())
+      assert(StringUtils.isNotBlank(rs.getString(1)))
+    }
+  }
+
   // dockerfile use kyuubi as user which is not same with non-k8s env.
   ignore("kyuubi defined function - system_user") {
     withJdbcStatement() { statement =>