database: rework connection logic

src/database.js

@@ -14,7 +14,6 @@ exports = module.exports = {
 
 var assert = require('assert'),
     async = require('async'),
-    BoxError = require('./boxerror.js'),
     child_process = require('child_process'),
     constants = require('./constants.js'),
     debug = require('debug')('box:database'),
@@ -22,8 +21,7 @@ var assert = require('assert'),
     once = require('once'),
     util = require('util');
 
-var gConnectionPool = null,
+var gConnectionPool = null;
-    gDefaultConnection = null;
 
 const gDatabase = {
     hostname: '127.0.0.1',
@@ -43,14 +41,16 @@ function initialize(callback) {
         gDatabase.hostname = require('child_process').execSync('docker inspect -f "{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}" mysql-server').toString().trim();
     }
 
+    // https://github.com/mysqljs/mysql#pool-options
     gConnectionPool  = mysql.createPool({
-        connectionLimit: 5, // this has to be > 1 since we store one connection as 'default'. the rest for transactions
+        connectionLimit: 5,
         host: gDatabase.hostname,
         user: gDatabase.username,
         password: gDatabase.password,
         port: gDatabase.port,
         database: gDatabase.name,
         multipleStatements: false,
+        waitForConnections: true, // getConnection() will wait until a connection is avaiable
         ssl: false,
         timezone: 'Z' // mysql follows the SYSTEM timezone. on Cloudron, this is UTC
     });
@@ -58,55 +58,20 @@ 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.on('error', (error) => debug(`Connection ${connection.threadId} error: ${error.message} ${error.code}`));
 
         connection.query('USE ' + gDatabase.name);
         connection.query('SET SESSION sql_mode = \'strict_all_tables\'');
     });
 
-    reconnect(callback);
+    callback();
 }
 
 function uninitialize(callback) {
-    if (gConnectionPool) {
+    if (!gConnectionPool) return callback(null);
+
     gConnectionPool.end(callback);
-        gDefaultConnection = null;
     gConnectionPool = null;
-    } else {
-        callback(null);
-    }
-}
-
-function reconnect(callback) {
-    callback = callback ? once(callback) : function () {};
-
-    debug('reconnect: connecting to database');
-
-    gConnectionPool.getConnection(function (error, connection) {
-        if (error) {
-            debug(`reconnect: db connection error. ${error.message} fatal:${error.fatal} code:${error.code}. Will retry in 10 seconds`);
-            return setTimeout(reconnect.bind(null, callback), 10000);
-        }
-
-        debug('reconnect: connected to database');
-
-        connection.on('error', function (error) {
-            // by design, we catch all normal errors by providing callbacks.
-            // 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');
-
-            debug(`reconnect: db connection error. ${error.message} fatal:${error.fatal} code:${error.code}. Will retry in 10 seconds`);
-
-            gDefaultConnection = null;
-
-            // This is most likely an issue an can cause double callbacks from reconnect()
-            setTimeout(reconnect.bind(null, callback), 10000);
-        });
-
-        gDefaultConnection = connection;
-
-        callback(null);
-    });
 }
 
 function clear(callback) {
@@ -119,40 +84,12 @@ function clear(callback) {
     child_process.exec(cmd, callback);
 }
 
-function beginTransaction(callback) {
-    assert.strictEqual(typeof callback, 'function');
-
-    if (gConnectionPool === null) return callback(new BoxError(BoxError.DATABASE_ERROR, 'No database connection pool.'));
-
-    gConnectionPool.getConnection(function (error, connection) {
-        if (error) return callback(error);
-
-        connection.beginTransaction(function (error) {
-            if (error) return callback(error);
-
-            return callback(null, connection);
-        });
-    });
-}
-
 function query() {
     var args = Array.prototype.slice.call(arguments);
     var callback = args[args.length - 1];
     assert.strictEqual(typeof callback, 'function');
 
-    if (gDefaultConnection === null) return callback(new BoxError(BoxError.DATABASE_ERROR, 'No connection to database'));
+    gConnectionPool.query.apply(gConnectionPool, args); // this is same as getConnection/query/release
-
-    gDefaultConnection.query.apply(gDefaultConnection, args);
-}
-
-function rollback(connection, transactionError, callback) {
-    connection.rollback(function (error) {
-        if (error) debug('rollback: error when rolling back', error);
-
-        connection.release();
-
-        callback(transactionError);
-    });
 }
 
 function transaction(queries, callback) {
@@ -161,16 +98,21 @@ function transaction(queries, callback) {
 
     callback = once(callback);
 
-    beginTransaction(function (error, connection) {
+    gConnectionPool.getConnection(function (error, connection) {
         if (error) return callback(error);
 
+        const releaseConnection = (error) => { connection.release(); callback(error); };
+
+        connection.beginTransaction(function (error) {
+            if (error) return releaseConnection(error);
+
             async.mapSeries(queries, function iterator(query, done) {
                 connection.query(query.query, query.args, done);
             }, function seriesDone(error, results) {
-            if (error) return rollback(connection, error, callback);
+                if (error) return connection.rollback(() => releaseConnection(error));
 
                 connection.commit(function (error) {
-                if (error) return rollback(connection, error, callback);
+                    if (error) return connection.rollback(() => releaseConnection(error));
 
                     connection.release();
 
@@ -178,6 +120,7 @@ function transaction(queries, callback) {
                 });
             });
         });
+    });
 }
 
 function importFromFile(file, callback) {