Fix crash when mysql crashes

src/database.js

@@ -56,6 +56,10 @@ function initialize(callback) {
     });
 
     gConnectionPool.on('connection', function (connection) {
+        // connection objects are re-used. so we have to attach to the event here (once) to prevent crash
+        // note the pool also has an 'acquire' event but that is called whenever we do a getConnection()
+        connection.on('error', (error) => debug(`Connection ${connection.threadId} error: ${error.message}`));
+
         connection.query('USE ' + gDatabase.name);
         connection.query('SET SESSION sql_mode = \'strict_all_tables\'');
     });
@@ -145,7 +149,6 @@ function rollback(connection, transactionError, callback) {
     connection.rollback(function (error) {
         if (error) debug('rollback: error when rolling back', error);
 
-        connection.removeAllListeners('error');
         connection.release();
 
         callback(transactionError);
@@ -161,8 +164,6 @@ function transaction(queries, callback) {
     beginTransaction(function (error, connection) {
         if (error) return callback(error);
 
-        connection.on('error', callback);
-
         async.mapSeries(queries, function iterator(query, done) {
             connection.query(query.query, query.args, done);
         }, function seriesDone(error, results) {
@@ -171,7 +172,6 @@ function transaction(queries, callback) {
             connection.commit(function (error) {
                 if (error) return rollback(connection, error, callback);
 
-                connection.removeAllListeners('error');
                 connection.release();
 
                 callback(null, results);