Trying to improve exception handling and resource closing in CreateCluster.

h2/src/main/org/h2/tools/CreateCluster.java

@@ -18,6 +18,7 @@ import org.h2.util.Tool;
 
 import java.io.PipedReader;
 import java.io.PipedWriter;
+import java.io.IOException;
 import java.sql.ResultSet;
 
 /**
@@ -143,8 +144,22 @@ public class CreateCluster extends Tool {
             // so that data can't change while restoring the second database
             statSource.execute("SET EXCLUSIVE 2");
 
+            // Pipe reader should be declared outside the try block to be visible in finally{}.
+            // It can be safely initialized here as it throws no exceptions.
+            PipedReader pipeReader = new PipedReader();
+            
             try {
-
+	        // Pipe writer is used + closed in the inner class, in a separate thread (needs to be final).
+	        // It should be initialized within try{} so an exception could be caught if creation fails.
+	        // In that scenario, the the writer should be null and needs no closing,
+	        // and the main goal is that finally{} should bring the source DB
+	        // out of exclusive mode, and close the reader.
+                final PipedWriter pipeWriter = new PipedWriter(pipeReader);
+                
+                // Backup data from source database in script form.
+                // Start writing to pipe writer in separate thread.
+                final ResultSet rs = statSource.executeQuery("SCRIPT");
+                
                 // Delete the target database first.
                 connTarget = DriverManager.getConnection(
                         urlTarget + ";CLUSTER=''", user, password);
@@ -152,29 +167,28 @@ public class CreateCluster extends Tool {
                 statTarget.execute("DROP ALL OBJECTS DELETE FILES");
                 connTarget.close();
 
-                // Backup data from source database in script form.
-                // Start writing to script pipe output end in separate thread.
-                // Variables used from inner class must be final.
-                final PipedReader pipeReader = new PipedReader();
-                final ResultSet rs = statSource.executeQuery("SCRIPT");
                 
                 new Thread(
                     new Runnable(){
                         public void run() {
                             try {
-                                PipedWriter pipeWriter = new PipedWriter(pipeReader);
                                 while (rs.next()) {
                                     pipeWriter.write(rs.getString(1) + "\n");
                                 }
-                                pipeWriter.close();
-                            } catch (Exception e ) {
-                                throw new IllegalStateException("Producing script from the source DB is failing.");
+                            } catch (Exception eScript) {
+                                throw new IllegalStateException("Producing script from the source DB is failing.",eScript);
+                            } finally {
+                                try {
+                                    pipeWriter.close();
+                                } catch (IOException eCloseWriter) {
+				    throw new IllegalStateException("Closing the pipe writer failed.",eCloseWriter);
+                                }
                             }
                         }
                     }
                 ).start();
                 
-                // Read data from script pipe input end, restore on target.
+                // Read data from pipe reader, restore on target.
                 connTarget = DriverManager.getConnection(urlTarget, user, password);
                 RunScript runScript = new RunScript();
                 runScript.setOut(out);
@@ -184,10 +198,19 @@ public class CreateCluster extends Tool {
                 // set the cluster to the serverList on both databases
                 statSource.executeUpdate("SET CLUSTER '" + serverList + "'");
                 statTarget.executeUpdate("SET CLUSTER '" + serverList + "'");
+                
+            } catch (IOException eAttach) {
+                throw new IllegalStateException("Failed attaching pipe writer to pipe reader.",eAttach);
+                
             } finally {
-
                 // switch back to the regular mode
                 statSource.execute("SET EXCLUSIVE FALSE");
+                
+                try {
+                    pipeReader.close();
+                } catch (Exception eCloseReader) {
+                    throw new IllegalStateException("Failed closing the pipe reader.",eCloseReader);
+                }
             }
         } finally {
             JdbcUtils.closeSilently(statSource);