release pool connection restores pool user configuration

lib/PoolConnection.js

@@ -23,13 +23,44 @@ PoolConnection.prototype.changeUser = function changeUser(options, callback) {
   return __changeUser.apply(this, arguments);
 };
 
+PoolConnection.prototype.restoreUser = function restoreUser(callback) {
+  var poolConfig = this._pool.config.connectionConfig;
+
+  var connection = this;
+  var config = connection.config;
+  var user = poolConfig.user;
+  var database = poolConfig.database;
+  var password = poolConfig.password;
+
+  // only when credentials have been changed from the pool defaults
+  if (config.user !== user || config.database !== database || config.password !== password) {
+    connection.changeUser({ user: user, database: database, password: password }, function (err) {
+      if (err) return callback(err);
+      // emit as if it were a new connection so consumers can setup session state again
+      connection._pool.emit('connection', connection);
+      callback(null);
+    });
+    connection._purge = false;
+  } else {
+    callback();
+  }
+}
+
 PoolConnection.prototype.release = function release() {
   var pool = this._pool;
+  var connection = this;
 
   if (!pool || pool._closed) {
     return;
   }
 
+  if (this._purge) {
+    return this.restoreUser(function (err) {
+      if (err) return connection.destroy();
+      pool.releaseConnection(connection);
+    });
+  }
+
   return pool.releaseConnection(this);
 };
 

test/unit/pool/test-change-user-eject.js

@@ -9,23 +9,31 @@ var pool   = common.createPool({
 var closed = 0;
 var server = common.createFakeServer();
 var thread = 0;
+var connections = 0;
 
 server.listen(common.fakeServerPort, function(err) {
   assert.ifError(err);
 
+  pool.on('connection', function(conn) {
+    connections++;
+  });
+
   var conn0;
   pool.getConnection(function(err, conn) {
     assert.ifError(err);
     assert.strictEqual(conn.threadId, 1);
+    assert.strictEqual(connections, 1);
     conn0 = conn;
   });
 
   pool.getConnection(function(err, conn) {
     assert.ifError(err);
     assert.strictEqual(conn.threadId, 2);
+    assert.strictEqual(connections, 2);
 
     conn.changeUser({user: 'user_2'}, function(err) {
       assert.ifError(err);
+      assert.strictEqual(connections, 2);
       assert.strictEqual(conn.threadId, 2);
       conn.release();
       conn0.release();
@@ -34,17 +42,21 @@ server.listen(common.fakeServerPort, function(err) {
 
   pool.getConnection(function(err, conn1) {
     assert.ifError(err);
+    assert.strictEqual(connections, 2);
     assert.strictEqual(conn1.threadId, 1);
+    assert.strictEqual(conn1.config.user, 'user_1');
 
     pool.getConnection(function(err, conn2) {
       assert.ifError(err);
-      assert.strictEqual(conn2.threadId, 3);
+      assert.strictEqual(connections, 3);
+      assert.strictEqual(conn1.config.user, 'user_1');
+      assert.strictEqual(conn2.threadId, 2);
       conn1.release();
       conn2.release();
 
       pool.end(function(err) {
         assert.ifError(err);
-        assert.strictEqual(closed, 3);
+        assert.strictEqual(closed, 2);
         server.destroy();
       });
     });