[GitHub] [spark] maropu commented on a change in pull request #29024: [SPARK-32001][SQL]Create JDBC authentication provider developer API

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maropu commented on a change in pull request #29024:
URL: https://github.com/apache/spark/pull/29024#discussion_r500975741



##########
File path: sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/connection/ConnectionProvider.scala
##########
@@ -18,60 +18,45 @@
 package org.apache.spark.sql.execution.datasources.jdbc.connection
 
 import java.sql.{Connection, Driver}
-import java.util.Properties
+import java.util.ServiceLoader
 
-import org.apache.spark.internal.Logging
-import org.apache.spark.sql.execution.datasources.jdbc.JDBCOptions
-
-/**
- * Connection provider which opens connection toward various databases (database specific instance
- * needed). If kerberos authentication required then it's the provider's responsibility to set all
- * the parameters.
- */
-private[jdbc] trait ConnectionProvider {
-  /**
-   * Additional properties for data connection (Data source property takes precedence).
-   */
-  def getAdditionalProperties(): Properties = new Properties()
+import scala.collection.mutable
 
-  /**
-   * Opens connection toward the database.
-   */
-  def getConnection(): Connection
-}
+import org.apache.spark.internal.Logging
+import org.apache.spark.security.SecurityConfigurationLock
+import org.apache.spark.sql.jdbc.JdbcConnectionProvider
+import org.apache.spark.util.Utils
 
 private[jdbc] object ConnectionProvider extends Logging {
-  def create(driver: Driver, options: JDBCOptions): ConnectionProvider = {
-    if (options.keytab == null || options.principal == null) {
-      logDebug("No authentication configuration found, using basic connection provider")
-      new BasicConnectionProvider(driver, options)
-    } else {
-      logDebug("Authentication configuration found, using database specific connection provider")
-      options.driverClass match {
-        case PostgresConnectionProvider.driverClass =>
-          logDebug("Postgres connection provider found")
-          new PostgresConnectionProvider(driver, options)
-
-        case MariaDBConnectionProvider.driverClass =>
-          logDebug("MariaDB connection provider found")
-          new MariaDBConnectionProvider(driver, options)
-
-        case DB2ConnectionProvider.driverClass =>
-          logDebug("DB2 connection provider found")
-          new DB2ConnectionProvider(driver, options)
-
-        case MSSQLConnectionProvider.driverClass =>
-          logDebug("MS SQL connection provider found")
-          new MSSQLConnectionProvider(driver, options)
-
-        case OracleConnectionProvider.driverClass =>
-          logDebug("Oracle connection provider found")
-          new OracleConnectionProvider(driver, options)
-
-        case _ =>
-          throw new IllegalArgumentException(s"Driver ${options.driverClass} does not support " +
-            "Kerberos authentication")
+  private val providers = loadProviders()
+
+  def loadProviders(): Seq[JdbcConnectionProvider] = {
+    val loader = ServiceLoader.load(classOf[JdbcConnectionProvider],
+      Utils.getContextOrSparkClassLoader)
+    val providers = mutable.ArrayBuffer[JdbcConnectionProvider]()
+
+    val iterator = loader.iterator
+    while (iterator.hasNext) {
+      try {
+        val provider = iterator.next
+        logDebug(s"Loaded built in provider: $provider")
+        providers += provider
+      } catch {
+        case t: Throwable =>
+          logError(s"Failed to load built in provider.", t)

Review comment:
       Is it okay to ignore the error case where it fails to load *builtin* providers? `DataSource` throws an exception if it fails to load builtin datasources:
   https://github.com/apache/spark/blob/94d648dff5f24b4dea3873fd8e6609b1a099d0a2/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/DataSource.scala#L694-L702




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