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Introduction to Messaging
- 1. Introduction to Messaging Donald Belcham
- 2. wat?
- 6. Y U WANT?
- 21. Your App Your Backend App Your Backend App 2 Your Backend App 3 Your Backend App 1
Editor's Notes
- Messaging is a way to communicate
- Allows us to connect two or more completely separate systems
- Systems don’t have to be tightly connected to work with each other.
- There are a lot of demands placed on business software. Really they’re expectations, not demands...and many of them are entirely reasonable
- Business expectations of how the application should work are at the top of the list
- We’re left to figure out how to realize those business expectations via technology
- The business has asked for things like Reliability USS Reliable served throughout WWII without any notable actions/problems/incidents
- The business expects to have confirmation that a credit card has been charged before beginning to ship the product to the customer. No payment confirmation, no shipping.
- We rely on transactions if possible or “manually” rolling back the data which is more likely
- And Resiliency HMS Hardy...which was badly damaged by German destroyers during the Norway campaign of WWII and had to be run aground so as not to sink. The rising tide lifted her off the bottom and she capsized and was lost.
- When an external system goes offline, they expect that it will not affect their systems
- Usually this means we retry the request/communication with the 3rd party. But we can’t retry forever
- Immediate retires, delayed retries, manual retries
- And scalability
- They want known spikes in traffic/usage to be handled without crippling the system and losing those sales/customers
- Most commonly, infrastructure is built to the highest expected capacity and then run at a fraction of that for the majority of the time
- They want their highest revenue customers to be treated with the priority that they deserve.
- People start talking about multi-tenancy, stand alone systems for high value customers and other ‘duplicative’ solutions.
- The way we historically, and currently, build apps makes overcoming these issues quite difficult.
- Changing to messaging requires changing how you think Compensating actions instead of transactions “Events” and “commands” Idempotency “Immediate” usually means “less than X minutes/hours/days from now”