feat: add dump function for current connections count

lib/Pool.js

@@ -285,6 +285,16 @@ Pool.prototype.escapeId = function escapeId(value) {
   return mysql.escapeId(value, false);
 };
 
+Pool.prototype.getConnectionCounts = function () {
+  return {
+    allConnectionsCount       : this._allConnections.length,
+    idleConnectionsCount      : this._freeConnections.length,
+    connectionQueueCount      : this._connectionQueue.length,
+    acquiringConnectionsCount : this._acquiringConnections.length,
+    busyConnectionsCount      : this._allConnections.length - this._freeConnections.length - this._acquiringConnections.length
+  };
+};
+
 function spliceConnection(array, connection) {
   var index;
   if ((index = array.indexOf(connection)) !== -1) {

test/unit/pool/test-get-connection-counts.js

@@ -0,0 +1,100 @@
+var assert = require('assert');
+var common = require('../../common');
+
+var server = common.createFakeServer();
+
+server.listen(0, function (err) {
+  assert.ifError(err);
+
+  var connectionLimit = 3;
+  var pool = common.createPool({ port: server.port(), connectionLimit: connectionLimit } );
+  assert.equal(connectionLimit, pool.config.connectionLimit);
+  assert.equal(pool.getConnectionCounts().allConnectionsCount, 0);
+  assert.equal(pool.getConnectionCounts().idleConnectionsCount, 0);
+  assert.equal(pool.getConnectionCounts().connectionQueueCount, 0);
+  assert.equal(pool.getConnectionCounts().acquiringConnectionsCount, 0);
+  assert.equal(pool.getConnectionCounts().busyConnectionsCount, 0);
+
+  var conn1, conn2, conn3, conn4, conn5;
+
+  pool.getConnection(function (err, connection) {
+    assert.ifError(err);
+    conn1 = connection;
+  });
+
+  pool.getConnection(function (err, connection) {
+    assert.ifError(err);
+    conn2 = connection;
+  });
+  pool.getConnection(function (err, connection) {
+    assert.ifError(err);
+    conn3 = connection;
+  });
+  pool.getConnection(function (err, connection) {
+    assert.ifError(err);
+    conn4 = connection;
+  });
+  pool.getConnection(function (err, connection) {
+    assert.ifError(err);
+    conn5 = connection;
+  });
+
+  setTimeout(function(){
+    assert.ok(conn1);
+    assert.ok(conn2);
+    assert.ok(conn3);
+    assert.ok(conn4 === undefined);
+    assert.ok(conn5 === undefined);
+    assert.equal(pool.getConnectionCounts().allConnectionsCount, 3);
+    assert.equal(pool.getConnectionCounts().idleConnectionsCount, 0);
+    assert.equal(pool.getConnectionCounts().connectionQueueCount, 2);
+    assert.equal(pool.getConnectionCounts().acquiringConnectionsCount, 0);
+    assert.equal(pool.getConnectionCounts().busyConnectionsCount, 3);
+
+    pool.releaseConnection(conn1);
+    assert.equal(pool.getConnectionCounts().allConnectionsCount, 3);
+    assert.equal(pool.getConnectionCounts().idleConnectionsCount, 0);
+    assert.equal(pool.getConnectionCounts().connectionQueueCount, 1);
+    assert.equal(pool.getConnectionCounts().acquiringConnectionsCount, 1);
+    assert.equal(pool.getConnectionCounts().busyConnectionsCount, 2);
+
+    setTimeout(function() {
+      assert.ok(conn4);
+      assert.ok(conn5 === undefined);
+      assert.equal(pool.getConnectionCounts().allConnectionsCount, 3);
+      assert.equal(pool.getConnectionCounts().idleConnectionsCount, 0);
+      assert.equal(pool.getConnectionCounts().connectionQueueCount, 1);
+      assert.equal(pool.getConnectionCounts().acquiringConnectionsCount, 0);
+      assert.equal(pool.getConnectionCounts().busyConnectionsCount, 3);
+
+      pool.releaseConnection(conn2);
+      pool.releaseConnection(conn3);
+      pool.releaseConnection(conn4);
+      assert.equal(pool.getConnectionCounts().allConnectionsCount, 3);
+      assert.equal(pool.getConnectionCounts().idleConnectionsCount, 2);
+      assert.equal(pool.getConnectionCounts().connectionQueueCount, 0);
+      assert.equal(pool.getConnectionCounts().acquiringConnectionsCount, 1);
+      assert.equal(pool.getConnectionCounts().busyConnectionsCount, 0);
+
+      setTimeout(function() {
+        assert.ok(conn5);
+        pool.releaseConnection(conn5);
+        assert.equal(pool.getConnectionCounts().allConnectionsCount, 3);
+        assert.equal(pool.getConnectionCounts().idleConnectionsCount, 3);
+        assert.equal(pool.getConnectionCounts().connectionQueueCount, 0);
+        assert.equal(pool.getConnectionCounts().acquiringConnectionsCount, 0);
+        assert.equal(pool.getConnectionCounts().busyConnectionsCount, 0);
+        pool.end(function(err){
+          assert.ifError(err);
+          assert.equal(pool.getConnectionCounts().allConnectionsCount, 0);
+          assert.equal(pool.getConnectionCounts().idleConnectionsCount, 0);
+          assert.equal(pool.getConnectionCounts().connectionQueueCount, 0);
+          assert.equal(pool.getConnectionCounts().acquiringConnectionsCount, 0);
+          assert.equal(pool.getConnectionCounts().busyConnectionsCount, 0);
+          server.destroy();
+        });
+      }, 100);
+    }, 100);
+  }, 100);
+
+});