[CALCITE-1060] Fix test deadlock by initializing DriverManager before registering AlternatingDriver

vlsi · julianhyde · commit 62576556abd0 · 2016-01-18T11:02:02.000-08:00
Early DriverManager initialization is required to prevent Driver.<clinit> -> DriverManager.findServiceProviders -> Class.forName("Driver") deadlock. Note: proper resolution might need to add an entry for "AlternatingDriver" to the service manifest. Close apache#185
diff --git a/avatica-server/src/test/java/org/apache/calcite/avatica/remote/AlternatingRemoteMetaTest.java b/avatica-server/src/test/java/org/apache/calcite/avatica/remote/AlternatingRemoteMetaTest.java
@@ -68,6 +68,10 @@ public class AlternatingRemoteMetaTest {
 
   static {
     try {
+      // Force DriverManager initialization before we hit AlternatingDriver->Driver.<clinit>
+      // Otherwise Driver.<clinit> -> DriverManager.registerDriver -> scan service provider files
+      // causes a deadlock; see [CALCITE-1060]
+      DriverManager.getDrivers();
       DriverManager.registerDriver(new AlternatingDriver());
     } catch (SQLException e) {
       throw new RuntimeException(e);
