update protocol

8 files changed, 469 insertions, 137 deletions

diff --git a/README.md b/README.md
index 382d7e0..3061dee 100644
--- a/README.md
+++ b/README.md
@@ -42,6 +42,21 @@ CREATE TABLE `jobs` (
 
 For optimization purposes, you can turn fields `target` and `slot` into `ENUM`s.
 
+
+## TODO
+
+**jobd**:
+- `pause(targets)` / `continue(targets)`
+- `runManual` with multiple jobs
+
+**jobd-master**:
+- `status(workers=true)`
+- `pause(targets)` / `continue(targets)`
+
+both:
+- text protocol
+
+
 ## License
 
 BSD-2c
\ No newline at end of file
diff --git a/src/jobd-master.js b/src/jobd-master.js
index 608750d..d6bc09a 100755
--- a/src/jobd-master.js
+++ b/src/jobd-master.js
@@ -65,7 +65,9 @@ async function main() {
 
     // start server
     server = new Server()
-    server.on('message', onMessage)
+    server.on('new-connection', (connection) => {
+        connection.on('request-message', onRequestMessage)
+    })
     server.start(config.get('port'), config.get('host'))
     logger.info('server started')
 }
@@ -75,65 +77,71 @@ async function main() {
  * @param {Connection} connection
  * @return {Promise<*>}
  */
-async function onMessage({message, connection}) {
+async function onRequestMessage(message, connection) {
     try {
-        if (!(message instanceof RequestMessage)) {
-            logger.debug('ignoring message', message)
-            return
-        }
-
-        if (message.requestType !== 'ping')
-            logger.info('onMessage:', message)
-
-        if (config.get('password') && message.password !== config.get('password')) {
-            connection.send(new ResponseMessage().setError('invalid password'))
-            return connection.close()
-        }
+        logger.info('onMessage:', message)
 
         switch (message.requestType) {
-            case 'ping':
-                connection.send(new ResponseMessage().setError('pong'))
-                break
-
             case 'register-worker': {
                 const targets = message.requestData?.targets || []
                 if (!targets.length) {
-                    connection.send(new ResponseMessage().setError(`targets are empty`))
+                    connection.send(
+                        new ResponseMessage(message.requestNo)
+                            .setError(`targets are empty`)
+                    )
                     break
                 }
 
                 workers.add(connection, targets)
-                connection.send(new ResponseMessage().setData('ok'))
+                connection.send(
+                    new ResponseMessage(message.requestNo)
+                        .setData('ok')
+                )
                 break
             }
 
             case 'poke': {
                 const targets = message.requestData?.targets || []
                 if (!targets.length) {
-                    connection.send(new ResponseMessage().setError(`targets are empty`))
+                    connection.send(
+                        new ResponseMessage(message.requestNo)
+                            .setError(`targets are empty`)
+                    )
                     break
                 }
 
                 workers.poke(targets)
-                connection.send(new ResponseMessage().setData('ok'))
+                connection.send(
+                    new ResponseMessage(message.requestNo)
+                        .setData('ok')
+                )
                 break
             }
 
             case 'status':
                 const info = workers.getInfo()
-                connection.send(new ResponseMessage().setData({
-                    workers: info,
-                    memoryUsage: process.memoryUsage()
-                }))
+                connection.send(
+                    new ResponseMessage(message.requestNo)
+                        .setData({
+                            workers: info,
+                            memoryUsage: process.memoryUsage()
+                        })
+                )
                 break
 
             default:
-                connection.send(new ResponseMessage().setError(`unknown request type: '${message.requestType}'`))
+                connection.send(
+                    new ResponseMessage(message.requestNo)
+                        .setError(`unknown request type: '${message.requestType}'`)
+                )
                 break
         }
     } catch (error) {
         logger.error(`error while handling message:`, message, error)
-        connection.send(new ResponseMessage().setError('server error: ' + error?.message))
+        connection.send(
+            new ResponseMessage(message.requestNo)
+                .setError('server error: ' + error?.message)
+        )
     }
 }
 
diff --git a/src/jobd.js b/src/jobd.js
index a175b63..0df4e70 100755
--- a/src/jobd.js
+++ b/src/jobd.js
@@ -22,7 +22,7 @@ let logger
 let server
 
 /**
- * @type {object.<string, Connection>}
+ * @type {object.<string, {connection: Connection, requestNo: number}>}
  */
 let jobDoneAwaiters = {}
 
@@ -90,8 +90,14 @@ async function main() {
     }
     worker.on('job-done', (data) => {
         if (jobDoneAwaiters[data.id] !== undefined) {
-            jobDoneAwaiters[data.id].send(new ResponseMessage().setData(data))
-            jobDoneAwaiters[data.id].close()
+            const {connection, requestNo} = jobDoneAwaiters[data.id]
+
+            connection.send(
+                new ResponseMessage(requestNo)
+                    .setData(data)
+            )
+            connection.close()
+
             delete jobDoneAwaiters[data.id]
         }
     })
@@ -99,7 +105,9 @@ async function main() {
 
     // start server
     server = new Server()
-    server.on('message', onMessage)
+    server.on('new-connection', (connection) => {
+        connection.on('request-message', onRequestMessage)
+    })
     server.start(config.get('port'), config.get('host'))
     logger.info('server started')
 
@@ -114,36 +122,27 @@ async function main() {
  * @param {Connection} connection
  * @return {Promise<*>}
  */
-async function onMessage({message, connection}) {
+async function onRequestMessage(message, connection) {
     try {
-        if (!(message instanceof RequestMessage)) {
-            logger.debug('ignoring message', message)
-            return
-        }
-
-        if (message.requestType !== 'ping')
-            logger.info('onMessage:', message)
-
-        if (config.get('password') && message.password !== config.get('password')) {
-            connection.send(new ResponseMessage().setError('invalid password'))
-            return connection.close()
-        }
+        logger.info('onMessage:', message)
 
         switch (message.requestType) {
-            case 'ping':
-                connection.send(new ResponseMessage().setData('pong'))
-                break
-
             case 'poll':
                 const targets = message.requestData?.targets || []
                 if (!targets.length) {
-                    connection.send(new ResponseMessage().setError('empty targets'))
+                    connection.send(
+                        new ResponseMessage(message.requestNo)
+                            .setError('empty targets')
+                    )
                     break
                 }
 
                 for (const t of targets) {
                     if (!worker.hasTarget(t)) {
-                        connection.send(new ResponseMessage().setError(`invalid target '${t}'`))
+                        connection.send(
+                            new ResponseMessage(message.requestNo)
+                                .setError(`invalid target '${t}'`)
+                        )
                         break
                     }
                 }
@@ -151,28 +150,38 @@ async function onMessage({message, connection}) {
                 worker.setPollTargets(targets)
                 worker.poll()
 
-                connection.send(new ResponseMessage().setData('ok'));
+                connection.send(
+                    new ResponseMessage(message.requestNo)
+                        .setData('ok')
+                )
                 break
 
             case 'status':
                 const qs = worker.getStatus()
                 connection.send(
-                    new ResponseMessage().setData({
-                        queue: qs,
-                        jobDoneAwaitersCount: Object.keys(jobDoneAwaiters).length,
-                        memoryUsage: process.memoryUsage()
-                    })
+                    new ResponseMessage(message.requestNo)
+                        .setData({
+                            queue: qs,
+                            jobDoneAwaitersCount: Object.keys(jobDoneAwaiters).length,
+                            memoryUsage: process.memoryUsage()
+                        })
                 )
                 break
 
             case 'run-manual':
                 const {id} = message.requestData
                 if (id in jobDoneAwaiters) {
-                    connection.send(new ResponseMessage().setError('another client is already waiting this job'))
+                    connection.send(
+                        new ResponseMessage(message.requestNo)
+                            .setError('another client is already waiting this job')
+                    )
                     break
                 }
 
-                jobDoneAwaiters[id] = connection
+                jobDoneAwaiters[id] = {
+                    connection,
+                    requestNo: message.requestNo
+                }
 
                 const {accepted, error} = await worker.getTasks(null, STATUS_MANUAL, {id})
                 if (!accepted) {
@@ -181,18 +190,28 @@ async function onMessage({message, connection}) {
                     let message = 'failed to run task'
                     if (typeof error === 'string')
                         message += `: ${error}`
-                    connection.send(new ResponseMessage().setError(message))
+
+                    connection.send(
+                        new ResponseMessage(message.requestNo)
+                            .setError(message)
+                    )
                 }
 
                 break
 
             default:
-                connection.send(new ResponseMessage().setError(`unknown request type: '${message.requestType}'`))
+                connection.send(
+                    new ResponseMessage(message.requestNo)
+                        .setError(`unknown request type: '${message.requestType}'`)
+                )
                 break
         }
     } catch (error) {
         logger.error(`error while handling message:`, message, error)
-        connection.send(new ResponseMessage().setError('server error: ' + error?.message))
+        connection.send(
+            new ResponseMessage(message.requestNo)
+                .setError('server error: ' + error?.message)
+        )
     }
 }
 
@@ -202,11 +221,17 @@ function connectToMaster() {
     connection.connect(config.get('master_host'), config.get('master_port'))
 
     connection.on('connect', function() {
-        connection.send(
+        connection.sendRequest(
             new RequestMessage('register-worker', {
                 targets: worker.getTargets()
             })
         )
+        .then(response => {
+            logger.debug('connectToMaster: response:', response)
+        })
+        .catch(error => {
+            logger.error('connectToMaster: error while awaiting response:', error)
+        })
     })
 
     connection.on('close', () => {
@@ -216,17 +241,7 @@ function connectToMaster() {
         }, config.get('master_reconnect_timeout') * 1000)
     })
 
-    connection.on('message', (message) => {
-        if (!(message instanceof RequestMessage)) {
-            logger.debug('message from master is not a request, hmm... skipping', message)
-            return
-        }
-
-        onMessage({message, connection})
-            .catch((error) => {
-                logger.error('connectToMaster: onMessage:', error)
-            })
-    })
+    connection.on('request-message', onRequestMessage)
 }
 
 
diff --git a/src/lib/config.js b/src/lib/config.js
index a59615e..eb1135d 100644
--- a/src/lib/config.js
+++ b/src/lib/config.js
@@ -112,7 +112,7 @@ function parseMasterConfig(file) {
 }
 
 /**
- * @param {string} key
+ * @param {string|null} key
  * @return {string|number|object}
  */
 function get(key = null) {
diff --git a/src/lib/data-validator.js b/src/lib/data-validator.js
new file mode 100644
index 0000000..276ea9b
--- /dev/null
+++ b/src/lib/data-validator.js
@@ -0,0 +1,71 @@
+const {isInteger, isObject} = require('lodash')
+const {getLogger} = require('./logger')
+
+const typeNames = {
+    'i': 'integer',
+    'n': 'number',
+    's': 'string',
+    'o': 'object',
+    'a': 'array',
+}
+
+const logger = getLogger('data-validator')
+
+/**
+ * @param {string} expectedType
+ * @param value
+ */
+function checkType(expectedType, value) {
+    switch (expectedType) {
+        case 'i':
+            return isInteger(value)
+        case 'n':
+            return typeof value === 'number'
+        case 's':
+            return typeof value === 'string'
+        case 'o':
+            return typeof value === 'object'
+        case 'a':
+            return Array.isArray(value)
+        default:
+            logger.error(`checkType: unknown type ${expectedType}`)
+            return false
+    }
+}
+
+/**
+ * @param {object} data
+ * @param {array} schema
+ */
+function validateMessageData(data, schema) {
+    if (!isObject(data))
+        throw new Error(`data is not an object`)
+
+    for (const field of schema) {
+        let [name, types, required] = field
+        if (!(name in data)) {
+            if (required)
+                throw new Error(`missing required field ${name}`)
+
+            continue
+        }
+
+        types = types.split('')
+
+        if (!types
+            .map(type => checkType(type, data[name]))
+            .some(result => result === true)) {
+
+            let error = `'${name}' must be `
+            if (types.length === 1) {
+                error += typeNames[types[0]]
+            } else {
+                error += 'any of: ' + types.map(t => typeNames[t]).join(', ')
+            }
+
+            throw new Error(error)
+        }
+    }
+}
+
+module.exports = {validateMessageData}
\ No newline at end of file
diff --git a/src/lib/server.js b/src/lib/server.js
index 08eadca..ca06a6d 100644
--- a/src/lib/server.js
+++ b/src/lib/server.js
@@ -1,14 +1,21 @@
 const net = require('net')
 const EventEmitter = require('events')
 const {getLogger} = require('./logger')
-const isObject = require('lodash/isObject')
+const random = require('lodash/random')
+const config = require('./config')
+const {createCallablePromise} = require('./util')
+const {validateMessageData} = require('./data-validator')
 
 const EOT = 0x04
+const REQUEST_NO_LIMIT = 999999
+
 
 class Message {
 
     static REQUEST = 0
     static RESPONSE = 1
+    static PING = 2
+    static PONG = 3
 
     /**
      * @param {number} type
@@ -20,37 +27,61 @@ class Message {
         this.type = type
     }
 
+    /**
+     * @return {array}
+     */
     getAsObject() {
         return [this.type]
     }
-
 }
 
 class ResponseMessage extends Message {
-    constructor() {
+    /**
+     * @param {number} requestNo
+     */
+    constructor(requestNo) {
         super(Message.RESPONSE)
 
+        this.requestNo = requestNo
         this.error = null
         this.data = null
     }
 
+    /**
+     * @param {string} error
+     * @return {ResponseMessage}
+     */
     setError(error) {
         this.error = error
         return this
     }
 
+    /**
+     * @param data
+     * @return {ResponseMessage}
+     */
     setData(data) {
         this.data = data
         return this
     }
 
+    /**
+     * @return {array}
+     */
     getAsObject() {
+        let response = {
+            no: this.requestNo
+        }
+
+        if (this.error !== null)
+            response.error = this.error
+
+        if (this.data !== null)
+            response.data = this.data
+
         return [
             ...super.getAsObject(),
-            [
-                this.error,
-                this.data
-            ]
+            response
         ]
     }
 }
@@ -77,16 +108,28 @@ class RequestMessage extends Message {
          * @type {null|string}
          */
         this.password = null
+
+        /**
+         * @type {null|number}
+         */
+        this.requestNo = null
     }
 
+    /**
+     * @return {array}
+     */
     getAsObject() {
         let request = {
+            no: this.requestNo,
             type: this.requestType
         }
 
         if (this.requestData)
             request.data = this.requestData
 
+        if (this.password)
+            request.password = this.password
+
         return [
             ...super.getAsObject(),
             request
@@ -99,8 +142,28 @@ class RequestMessage extends Message {
     setPassword(password) {
         this.password = password
     }
+
+    /**
+     * @param {number} no
+     */
+    setRequestNo(no) {
+        this.requestNo = no
+    }
 }
 
+class PingMessage extends Message {
+    constructor() {
+        super(Message.PING)
+    }
+}
+
+class PongMessage extends Message {
+    constructor() {
+        super(Message.PONG)
+    }
+}
+
+
 class Server extends EventEmitter {
 
     constructor() {
@@ -137,14 +200,10 @@ class Server extends EventEmitter {
     onConnection = (socket) => {
         let connection = new Connection()
         connection.setSocket(socket)
-        connection.on('message', (message) => {
-            this.emit('message', {
-                message,
-                connection
-            })
-        })
 
         this.logger.info(`new connection from ${socket.remoteAddress}:${socket.remotePort}`)
+
+        this.emit('new-connection', connection)
     }
 
     onListening = () => {
@@ -158,6 +217,7 @@ class Server extends EventEmitter {
 
 }
 
+
 class Connection extends EventEmitter {
 
     constructor() {
@@ -190,9 +250,32 @@ class Connection extends EventEmitter {
         this.remotePort = null
 
         /**
-         * @type {null|number}
+         * @type {boolean}
+         * @private
+         */
+        this._isAuthorized = config.get('password') === ''
+
+        /**
+         * @type {boolean}
+         * @private
          */
-        this.id = null
+        this._textConversationAllowed = false
+
+        /**
+         * @type {boolean}
+         */
+        this._isOutgoing = false
+
+        /**
+         * @type {number}
+         */
+        this._lastOutgoingRequestNo = random(0, REQUEST_NO_LIMIT)
+
+        /**
+         * @type {object.<number, Promise>}
+         * @private
+         */
+        this._requestPromises = {}
 
         this._setLogger()
     }
@@ -205,13 +288,14 @@ class Connection extends EventEmitter {
         if (this.socket !== null)
             throw new Error(`this Connection already has a socket`)
 
+        this._isOutgoing = true
+
         this.socket = new net.Socket()
         this.socket.connect({host, port})
 
         this.remoteAddress = host
         this.remotePort = port
 
-        this._setId()
         this._setLogger()
         this._setSocketEvents()
     }
@@ -225,7 +309,11 @@ class Connection extends EventEmitter {
         this.remoteAddress = socket.remoteAddress
         this.remotePort = socket.remotePort
 
-        this._setId()
+        if (this.remoteAddress === '127.0.0.1') {
+            this._isAuthorized = true
+            this._textConversationAllowed = true
+        }
+
         this._setLogger()
         this._setSocketEvents()
     }
@@ -235,14 +323,7 @@ class Connection extends EventEmitter {
      */
     _setLogger() {
         let addr = this.socket ? this.remoteAddr() : '?'
-        this.logger = getLogger(`<Connection ${this.id} ${addr}>`)
-    }
-
-    /**
-     * @private
-     */
-    _setId() {
-        this.id = Math.floor(Math.random() * 10000)
+        this.logger = getLogger(`<Connection ${addr}>`)
     }
 
     /**
@@ -304,76 +385,183 @@ class Connection extends EventEmitter {
 
         this.logger.trace(`processChunks (after parsing):`, this.data)
 
-        for (let message of messages) {
+        for (let rawMessage of messages) {
             try {
-                let buf = message.toString('utf-8')
+                let buf = rawMessage.toString('utf-8')
                 this.logger.debug(buf)
 
                 let json = JSON.parse(buf)
-                this._emitMessage(json)
+
+                // try to parse the message
+                let message
+                try {
+                    message = this._parseMessage(json)
+                } catch (e) {
+                    // message is malformed
+                    this.logger.error(e.message)
+
+                    // send error to the other size
+                    this.send(
+                        new ResponseMessage(0).setError(e.message)
+                    )
+
+                    continue
+                }
+
+                if (message instanceof PingMessage) {
+                    this.send(new PongMessage())
+                    continue
+                }
+
+                if (message instanceof PongMessage)
+                    continue
+
+                if (message instanceof RequestMessage) {
+                    if (!this._isAuthorized) {
+                        if (message.password !== config.get('password')) {
+                            this.send(new ResponseMessage(message.requestNo).setError('invalid password'))
+                            this.close()
+                            break
+                        }
+
+                        this._isAuthorized = true
+                    }
+
+                    this.emit('request-message', message, this)
+                }
+
+                if (message instanceof ResponseMessage) {
+                    if (message.requestNo in this._requestPromises) {
+                        const P = this._requestPromises[message.requestNo]
+                        delete this._requestPromises[message.requestNo]
+
+                        P.resolve(message)
+                    } else {
+                        this.logger.warn('received unexpected Response message:', message)
+                    }
+                }
             } catch (error) {
                 this.logger.error('failed to parse data as JSON')
-                this.logger.debug(message)
+                this.logger.debug(rawMessage)
             }
         }
     }
 
     /**
+     * Parse incoming message
+     *
      * @param {object} json
+     * @return {Message}
      * @private
+     * @throws Error
      */
-    _emitMessage(json) {
-        if (!Array.isArray(json)) {
-            this.logger.error('malformed message, JSON array expected', json)
-            return
-        }
+    _parseMessage(json) {
+        if (!Array.isArray(json))
+            throw new Error('JSON array expected, got: ' + json)
 
         let type = json.shift()
         let message
         switch (type) {
             case Message.REQUEST: {
                 let data = json.shift()
-                if (!data || !isObject(data)) {
-                    this.logger.error('malformed REQUEST message')
-                    return
+
+                try {
+                    validateMessageData(data, [
+                        // name      type    required
+                        ['type',     's',    true],
+                        ['no',       'i',    true],
+                        ['password', 's',    false],
+                        ['data',     'snoa', false]
+                    ])
+                } catch (e) {
+                    throw new Error(`malformed REQUEST message: ${e.message}`)
                 }
 
                 message = new RequestMessage(data.type, data.data || null)
+                message.setRequestNo(data.no)
                 if (data.password)
                     message.setPassword(data.password)
-                break
+
+                return message
             }
 
             case Message.RESPONSE: {
                 let data = json.shift()
-                if (!data || !Array.isArray(data) || data.length < 2) {
-                    this.logger.error('malformed RESPONSE message')
-                    return
+
+                try {
+                    validateMessageData(data, [
+                        // name   type     required
+                        ['no',    'i',     true],
+                        ['data',  'snoa',  false],
+                        ['error', 's',     false],
+                    ])
+                } catch (e) {
+                    throw new Error(`malformed RESPONSE message: ${e.message}`)
                 }
 
-                message = new ResponseMessage()
-                message.setError(data[0]).setData(data[1])
+                message = new ResponseMessage(data.no)
+                message.setError(data.error || null)
+                    .setData(data.data || null)
 
-                break
+                return message
             }
 
+            case Message.PING:
+                return new PingMessage()
+
+            case Message.PONG:
+                return new PongMessage()
+
             default:
-                this.logger.error(`malformed message, unexpected type ${type}`)
-                return
+                throw new Error(`unexpected type ${type}`)
+        }
+    }
+
+    /**
+     * Send request
+     *
+     * @param {RequestMessage} message
+     * @return {Promise}
+     */
+    sendRequest(message) {
+        if (!(message instanceof RequestMessage))
+            throw new Error('sendRequest only accepts RequestMessage, got:', message)
+
+        // send password once (when talking to jobd-master)
+        if (!this._isAuthorized) {
+            message.setPassword(config.get('password'))
+            this._isAuthorized = true
+        }
+
+        // assign request number
+        const no = this._getNextOutgoingRequestNo()
+        if (this._requestPromises[no] !== undefined) {
+            this.logger.error(`sendRequest: next request's No is ${no}, found a promise awaiting response with the same no, rejecting...`)
+            this._requestPromises[no].reject(new Error(`this should not happen, but another request needs this number (${no})`))
+            delete this._requestPromises[no]
         }
 
-        this.emit('message', message)
+        message.setRequestNo(no)
+
+        // send it
+        this.send(message)
+
+        // create and return promise
+        const P = createCallablePromise()
+        this._requestPromises[no] = P
+
+        return P
     }
 
     /**
+     * Send any Message
+     *
      * @type {Message} data
      * @param message
      */
     send(message) {
         if (!(message instanceof Message))
-            throw new Error('send expects Message, got', message)
-
-        // TODO set password!
+            throw new Error('send expects Message, got: ' + message)
 
         let json = JSON.stringify(message.getAsObject())
         let buf = Buffer.concat([
@@ -391,13 +579,20 @@ class Connection extends EventEmitter {
         }
     }
 
+    _getNextOutgoingRequestNo() {
+        this._lastOutgoingRequestNo++;
+        if (this._lastOutgoingRequestNo >= REQUEST_NO_LIMIT)
+            this._lastOutgoingRequestNo = 1
+        return this._lastOutgoingRequestNo
+    }
+
     /**
      */
     close() {
         try {
             this.socket.end()
             this.socket.destroy()
-            this._emitClose()
+            this._handleClose()
         } catch (error) {
             this.logger.error('close:', error)
         }
@@ -406,12 +601,17 @@ class Connection extends EventEmitter {
     /**
      * @private
      */
-    _emitClose() {
-        if (this._closeEmitted)
-            return
+    _handleClose() {
+        if (!this._closeEmitted) {
+            this._closeEmitted = true
+            this.emit('close')
+        }
+
+        for (const no in this._requestPromises) {
+            this._requestPromises[no].reject(new Error('socket is closed'))
+        }
 
-        this._closeEmitted = true
-        this.emit('close')
+        this._requestPromises = {}
     }
 
     onConnect = () => {
@@ -433,12 +633,12 @@ class Connection extends EventEmitter {
     }
 
     onClose = (hadError) => {
-        this._emitClose()
+        this._handleClose()
         this.logger.debug(`socket closed` + (hadError ? ` with error` : ''))
     }
 
     onError = (error) => {
-        this._emitClose()
+        this._handleClose()
         this.logger.warn(`socket error:`, error)
     }
     
@@ -448,5 +648,7 @@ module.exports = {
     Server,
     Connection,
     RequestMessage,
-    ResponseMessage
+    ResponseMessage,
+    PingMessage,
+    PongMessage,
 }
\ No newline at end of file
diff --git a/src/lib/util.js b/src/lib/util.js
index 6de07e5..a4e0025 100644
--- a/src/lib/util.js
+++ b/src/lib/util.js
@@ -5,5 +5,26 @@ module.exports = {
 
     isNumeric(n) {
         return !isNaN(parseFloat(n)) && isFinite(n)
+    },
+
+    /**
+     * Creates a Promise that can be resolved or rejected from the outside
+     *
+     * @param {Function} abortCallback
+     * @return {Promise}
+     */
+    createCallablePromise(abortCallback = null) {
+        let promise, resolve, reject
+        promise = new Promise(function(_resolve, _reject) {
+            resolve = _resolve
+            reject = _reject
+        })
+        promise.resolve = function(result) {
+            resolve(result)
+        }
+        promise.reject = function(result) {
+            reject(result)
+        }
+        return promise
     }
-}
\ No newline at end of file
+}
diff --git a/src/lib/workers-list.js b/src/lib/workers-list.js
index 620f711..ed436e0 100644
--- a/src/lib/workers-list.js
+++ b/src/lib/workers-list.js
@@ -1,7 +1,7 @@
 const intersection = require('lodash/intersection')
 const config = require('./config')
 const {getLogger} = require('./logger')
-const {RequestMessage} = require('./server')
+const {RequestMessage, PingMessage} = require('./server')
 const throttle = require('lodash/throttle')
 
 class WorkersList {
@@ -136,7 +136,7 @@ class WorkersList {
         this.workers
             .forEach(w => {
                 this.logger.trace(`sending ping to ${w.connection.remoteAddr()}`)
-                w.connection.send(new RequestMessage('ping'))
+                w.connection.send(new PingMessage())
             })
     }