Messaging Powered Front Ends

Elton StonemanMicrosoft MVP & Pluralsight Author

http://particular.net

Messaging Powered Front Ends

Introduction to ServiceInsight for NServiceBusMessaging Powered Front Ends

•Channel to the User

•Broadcast Notifications

•Targeted Responses

•Fault Tolerance

•Scaling Concerns

Outline


Any back-end communicationClient callback mechanism Mobile push / WebSockets / polling

Channel to the User

BroadcastAll clientsPub-sub style

TargetedSingle clientReq-resp style


Two-way comms over TCP/IPPersistent connection (SPA)SignalR adds fault-tolerance

WebSockets & SignalR

Server.NET HubCan invoke client calls

ClientConnects to HubCan invoke server calls


Demo: Broadcast Notifications

Noticeboard Web App WebSockets & Messaging


Client-server call with SignalRWeb Server publishes to Exchange

Broadcast Notifications

exchange: noticeboard

SendMailRequest


Exchange bound to QueuesWeb Server listens on Queue



SendMailRequestqueue: broadcast

queue: persist


Web server broadcasts to clientsClient renders new message



Multiple ServersAdditional Queues



Demo: Response Messages

Noticeboard Web App WebSockets & Messaging


Multiple message handlers

Targeted Responses


SendMailRequest

queue: broadcast

queue: persist


Dedicated reply queueSpecified in outgoing messagesWeb Server listens for replies

Targeted Responses


SendMailRequest

queue: reply-svr01

Sender: eltonContent: hiReplyTo: reply-svr01


Handlers act on messageSend reply with result

Targeted Responses

SendMailRequest

queue: persist

queue: reply-svr01

MailSavedEvent

HandlerFailedEvent


Handlers act on messageSend reply with result

Targeted Responses

queue: broadcast

queue: reply-svr01

MailBroadcastEvent

HandlerFailedEvent

SendMailRequest


Web server receives replyLooks up client & sends

Targeted Responses


But... you can do this just with SignalR


Persistence handler offline

Demo: Fault Tolerance


SendMailRequest

queue: broadcast

queue: persist X


Durable queuesMessages wait for handler

Fault Tolerance


SendMailRequest

queue: persist


Broadcast notification is easyTargeted response – not so much...

Scaling Concerns


SignalR fault toleranceHeartbeat checks connection

Scaling Concerns


Connection re-establishedLoad-balanced Web servers

Scaling Concerns


Messages to 'wrong' Reply Queue

Scaling Concerns

queue: reply-svr01 queue: reply-svr02


Instead of per-server Reply QueueCommon Reply Exchange

Scaling Concerns


•You need a channel to the client

•Messaging semantics: pub-sub & req-resp

•Maintain patterns with messaging

•Fault tolerance – persistent messages

•Scaling – broadcast and filter

Summary

Thank you

blog.sixeyed.com

@EltonStoneman

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