make rollback return an error

fixes #690

src/database.js

@@ -17,6 +17,7 @@ var assert = require('assert'),
     BoxError = require('./boxerror.js'),
     child_process = require('child_process'),
     constants = require('./constants.js'),
+    debug = require('debug')('box:database'),
     mysql = require('mysql'),
     once = require('once'),
     util = require('util');
@@ -76,7 +77,7 @@ function reconnect(callback) {
 
     gConnectionPool.getConnection(function (error, connection) {
         if (error) {
-            console.error('Unable to reestablish connection to database. Try again in 10 seconds.', error.message);
+            debug('reconnect: unable to reestablish connection to database. Try again in 10 seconds.', error.message);
             return setTimeout(reconnect.bind(null, callback), 10000);
         }
 
@@ -85,7 +86,7 @@ function reconnect(callback) {
             // this function should be invoked only when we have no callbacks pending and we have a fatal error
             assert(error.fatal, 'Non-fatal error on connection object');
 
-            console.error('Unhandled mysql connection error. Will reconnect in 10 seconds', error);
+            debug('reconnect: unhandled mysql connection error. Will reconnect in 10 seconds', error);
 
             // This is most likely an issue an can cause double callbacks from reconnect()
             setTimeout(reconnect.bind(null, callback), 10000);
@@ -123,23 +124,22 @@ function beginTransaction(callback) {
     });
 }
 
-function rollback(connection, callback) {
+function rollback(connection, commitError, callback) {
     assert.strictEqual(typeof callback, 'function');
 
     connection.rollback(function (error) {
-        if (error) console.error(error); // can this happen?
+        if (error) debug('rollback: error when rolloing back', error);
 
         connection.release();
-        callback(null);
+        callback(commitError);
     });
 }
 
-// FIXME: if commit fails, is it supposed to return an error ?
 function commit(connection, callback) {
     assert.strictEqual(typeof callback, 'function');
 
     connection.commit(function (error) {
-        if (error) return rollback(connection, callback);
+        if (error) return rollback(connection, error, callback);
 
         connection.release();
         return callback(null);