Post on 03-Aug-2020
transcript
EWD.js Architecture
Rob TweedM/Gateway Developments Ltd
Twitter: @rtweedEmail: rtweed@mgateway.com
Tuesday, 18 February 14
EWD.js Architecture
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EWD.js Architecture
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Child Process removed from available poolas soon as a request is sent to it
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EWD.js Architecture
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Child Process returned to available pool as soonas processing is completed
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EWD.js Architecture
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Each Child process handles only one request at a time
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EWD.js Development
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100%JavaScript
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EWD.js Messaging
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EventOccurs
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EWD.js Messaging
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JSONMessageCreated
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EWD.js Messaging
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MessageSent
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EWD.js Messaging
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MessageReceived
atback-end
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EWD.js Messaging
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MessageHandler
fired
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EWD.js Messaging
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_setDocument()
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EWD.js Messaging
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_getDocument()
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EWD.js Messaging
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Messagesentby
back-end
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EWD.js Messaging
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MessageReceived
bybrowser
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EWD.js Messaging
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JSONMessage
EventHandler
Fires
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EWD.js Messaging
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ModifyUI
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Send message from browser
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EWD.sockets.sendMessage({ type: "sendHelloWorld", params: { text: 'Hello World!', sender: 'Rob', date: new Date().toUTCString() } });
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Back-end Module
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module.exports = { onMessage: { sendHelloWorld: function(payload, ewd) { // do whatever is required with payload return {received: true}; // or any JSON } }};
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Back-end Module
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module.exports = { onMessage: { sendHelloWorld: function(payload, ewd) { // eg save payload to JSON store var store = new ewd.mumps.GlobalNode('myStore', [1]); store._setDocument(payload); return {savedInto: ‘myStore’}; } }};
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Browser-side Handler
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onMessage { sendHelloWorld: function(msgObject) { // do whatever you need to do with the incoming message, eg: var text = 'Your message was successfully saved into ' + messageObj.message.savedInto; toastr.clear(); toastr.info(text); } };
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No Polling!
• With WebSockets, the back-end can send a message at any time to:– a specific browser– all browsers running a specific EWD.js
application– all currently-connected browsers
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Back-end can send a message
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var savedMsg = new ewd.mumps.GlobalNode('myMessage', []); ewd.sendWebSocketMsg({ type: 'savedMessage', message: savedMsg._getDocument() });
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Node.js, but Synchronous Code!
• Your back-end code runs in a Node.js Child Process
• An EWD.js Child Process only handles a single request at a time so it can afford to use blocking, synchronous I/O
• If all Child Processes are busy, incoming requests are queued in the fully asynchronous master Node.js process
• Child Process pool size is configurable to match demand
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Tuesday, 18 February 14
Node.js, but Synchronous Code!
• Database connector interfaces used by EWD.js are synchronous
• Your back-end JavaScript logic can be written in easy-to-maintain, intuitive synchronous style
• No “callback hell” or pseudo-synchronous syntax
• Result: faster development, maintainable JavaScript logic
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Built-in secured Web Services
• Any back-end EWD.js JavaScript method can also be exposed as a JSON Web Service
• Access is automatically secured– HMAC-SHA256 digital signatures required for
every HTTP request– The same security used by Amazon Web
Services• Lightweight peer-to-peer access between
EWD.js systems 26
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Secured Linked Systems
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EWD.js requirements
• Ideally browsers that support HTML5 WebSockets– however, EWD.js uses Node.js socket.io
library• emulates websockets using other techniques if not
available• even works with old versions of Internet Explorer!
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