Kiddy

     

MySQL + Connection Pool + Promises

Quick Start

To install kiddy in your project run the following in your project root:

npm install kiddy

With the necessary configuration in place (see Configuration below), using Kiddy and MySQL promise wrapped queries is as simple as:

conn = null;
kiddy.touch()
.then(function (connection) {
	conn = connection;
	/*\
	|*| Database logic here.
	|*| Feel free to use the method conn.pq to preform a promise wrapped
	|*| mysql conn.query or the vanilla conn.query.
	\*/
	return conn.pq('SELECT 1');
})
.fail(function (err) {
	...
});

This snippet will create a connection pool using your config defined connection parameters and get you a connection from the pool for immediate use.

Normal Usage

To properly handle errors and release your connection when you are done, you code should probably look more like this:

import * as kiddy from 'kiddy';
let conn = null;
kiddy.touch()
.then(function (connection) {
	/*\
	|*| Save connection handle to release later
	\*/
	conn = connection;
	/*\
	|*| Database logic here, feel free to use the promise wrapped
	|*| method handle.pq to preform a mysql conn.query.
	\*/
	return conn.pq('SELECT 1');
})
.then(function (rows) {
	/*\
	|*| Query results, do stuff
	\*/
	console.log(rows);
	/*\
	|*| When done, release the connection as shown below
	\*/
	return kiddy.release(conn);
})
.then(function (msg) {
	conn = null;
	console.log(msg); // Connection released
})
.fail(function (err) {
	/*\
	|*| Any MySQL Errors will propagate to this rejection handler.
	\*/
	console.log(err); // An error message
	/*\
	|*| Release the handle if it is non-null
	\*/
	if (conn) {
		kiddy.release(conn);
		conn = null;
	}
});

This keeps your application's database logic simple and handles all of the errors that should occur. The connection is released after your query is complete, allowing the pool to reuse the connection.

Configuration

You have two simple options to configure your database connection when using Kiddy.

1. Kiddy can use your (gitignored) config file located at /config/default.json or /config/production.json (in production environments) using the config package. See the config manual for more info.

   Here is the necessary stanza:

    ...,
    "rdb": {
    	"host": "127.0.0.1",
    	"port": 3306,
    	"user": "dbUsername",
    	"password": "password",
    	"database": "database"
    },
    ...
   

   If the rdb (for relational database) key is not present, Kiddy will attempt to fall back to one called database or mysql.

   With this config file and the info above, Kiddy should Just Work ™, no need to call any configuration functions at all.

2. You can supply database connection information prior to using Kiddy in your project.

   If you don't have your database creds in a config file, why not include them in your project source code (this is a bad idea), or manually parse them from some other secure location outside of your source tree (good idea).

   Then call the following with your manually specified options:

    kiddy.setOptions({
    	"host": "127.0.0.1",
    	"port": 3306,
    	"user": "dbUsername",
    	"password": "password",
    	"database": "database"
    })
    .then(function (msg) {
    	console.log(msg);
    	// Kiddy options set successfully
    })
    .fail(function (err) {
    	console.log(err);
    	// An error message
    });
   

API

The Kiddy api is pretty straightforward.

promise kiddy.setOptions(options)

Optional method to override the default kiddy options at /config/default.json.

Return

Returns a promise which is resolved with a success message.

.then(function (msg) {
	console.log(msg); // Success
})

Error

On error, the promise is rejected with an error message.

.fail(function (err) {
	console.log(err.message); // Error message
})

Arguments

Accepts an object with the following properties defined:

{
	host: "127.0.0.1",
	port: 3306,
	user: "dbUsername",
	password: "password",
	database: "database"
}

promise kiddy.touch()

Get a MySQL connection from the connection pool. This method will lazly initialize the pool if it does not exist.

Return

Returns a promise which is resolved with a MySQL connection handle. You are advised to save the reference to the connection handle in order to release it when you are done.

.then(function (connection) {
	/*\
	|*| Save connection handle to release later
	\*/
	conn = connection;
	/*\
	|*| `conn` is an instance of pool.getConnection with added magic
	\*/
	return conn.pq('SELECT 1');
})

Error

On error, the promise is rejected with an error message.

.fail(function (err) {
	console.log(err.message); // Error message
})

Arguments

kiddy.touch does not accept any arguments or options.

promise conn.pq(options, values)

Preform a promise wrapped MySQL query using the specified options.

Return

Returns a promise which is resolved with a MySQL result set.

.then(function (result) {
	console.log(result); // The result set
})

Understanding Node-MySQL's Promise-Wrapped Results

Remember, since a promise can only be resolved with a discrete value (primitive, array or object), the result above is actually a multi-dimensional array which looks like this:

For SELECT statements:

[								// Outer array
	[							// Inner array 0, array of result rows
		RowDataPacket (object)
	],
	[							// Inner array 1, array of result fields
		FieldPacket (object)
	]
]

For INSERT, UPDATE or DELETE statements:

[
	OkPacket (object),
	undefined
]

Here is the breakdown on each of these low-level MySQL objects.

RowDataPacket - An object where each property corresponds to one of the fields in the select statement. For example if you are running the following query:

Select `id` FROM `mydb`.`mytable`

An individual RowDataPacket object would be:

{
	id: 2
}

for the first row of the result set.

FieldPacket - Field metadata containing the following properties:

{
	catalog: 'def',
	db: 'theDatabaseName',
	table: 'theTableNameAlias',
	orgTable: 'theTableName',
	name: 'fieldNameAlias',
	orgName: 'fieldName',
	charsetNr: 63,				// The field's character set
	length: 10,					// Size of the field
	type: 3,					// Type of the field
	flags: 16899,
	decimals: 0,				// Number of decimals
	default: undefined,			// The field's default value
	zeroFill: false,			// Whether this field is zero filled
	protocol41: true
}

OkPacket - MySQL statement results containing the following properties:

{
	fieldCount: 0,
	affectedRows: 1,			// Number of rows affected by query
	insertId: 0,				// AutoIncrement ID (if an INSERT)
	serverStatus: 2,
	warningCount: 0,
	message: '(Rows matched: 1  Changed: 1  Warnings: 0',
	protocol41: true,
	changedRows: 1				// Rows that were changed by the query
}

To make use of these promise resolved results, roll like this for a SELECT statement:

.then(function (data) {
	var rows = data[0];
	var fields = data[1];
	console.log(rows.length);	// Your row count
	console.log(rows[0]);		// Your first result
	console.log(fields.length); // The number of fields in the results
	console.log(fields[0]); 	// The first field's metadata
})

and like this for INSERT, UPDATE or DELETE statements:

.then(function (data) {
	var results = data[0];		// Your result object
	var fields = data[1];		// Undefined, ignore this
	console.log(results.affectedRows);	// Doing work son.
})

Error

On error, the promise is rejected with an error message.

.fail(function (err) {
	console.log(err.message); // Error message
})

Arguments

conn.pq accepts the same arguments that the underlying MySQL conn.query method accepts. These options can be:

1. An SQL string
2. An SQL string and an array of placeholder values
3. An options object

For more information, see the documentation for the node-mysql package.

promise kiddy.release(handle)

Releases a MySQL connection handle to the connection pool for reuse.

Return

Returns a promise which is resolved with a success message if the connection was released successfully.

.then(function (msg) {
	console.log(msg); // Success
})

Error

On error, the promise is rejected with an error message.

.fail(function (err) {
	console.log(err.message); // Error message
})

Arguments

kiddy.release accepts one mandatory argument which is the connection handle to release.

promise kiddy.drain(clear_cache = false)

Attempts to drain the MySQL connection pool and close all active connections. After a connection pool is drained, attempts to reuse any connection handles that are still active will result in undefined behavior.

A pool that has been drained can be refilled with a subsequent call to kiddy.touch() which will attempt to reconnect with cached credentials and refill the connection pool.

Return

Returns a promise which is resolved with a success message if the connection was released successfully.

.then(function (msg) {
	console.log(msg); // Success
})

Error

On error, the promise is rejected with an error message.

.fail(function (err) {
	console.log(err.message); // Error message
})

Arguments

kiddy.drain accepts one optional argument for whether or not the credential cache should be purged after the pool is drained. This option defaults to true. Pass in false to preserve the credential cache for later reuse.