2.8 geographically distributed architecture
architecture
resource group
Azure CDN
Content Delivery Network
global service caches static content at points of presence all around the world.
Azure search
allows us to make all content searchable, and provide search suggestions and fuzzy search results to our users.
azure front door
- poll multiple App Services
- global system
Regional Pairs
- area with a single geography that contains one or more Azure datacenters
- updates and planned maintenance are done on only one region at a time.
SLA
calculate the overall SLA for the app as a composite of all other services SLAs.
- multiplying together the SLAs of the component services
resource group doesn't limit us to use the same Azure region for the included resources
networking
Azure DNS
- inherently multi-regional
- SLA also has a 100% guarantee
traffic router
Azure Application Gateway
- single region bound
Azure Traffic Manager
Azure Front Door
- global load balancer
- uses DNS records to route traffic
priority routing mode
primary and secondary region
uses the DNS system to route traffic
- YES: it routes any protocol, not just HTTP traffic
- NO can't route or filter traffic based on HTTP properties, such as client country codes or user-agent headers
- NO: can't do Transport Layer Security (TLS) protocol termination
highly configurable: protocol, port, path, custom header, number of failures
- global load balancer
- it works at the network application layer, Layer 7, and uses HTTP and HTTPS properties to do filtering and routing
- YES: route traffic based on the browser's country code.
- YES: supports TLS protocol termination
- BUT: If we want to route traffic for any protocol other than HTTP and HTTPS, we'll have to use Traffic Manager.
- assign priorities to the various backends
- health probes
When should you perform a full failover to another region
- When you know definitively, that a region is down.
application
data
make sure the web application doesn't store any session state information in memory
storage account
geo redundancy is asynchronous
--> you can have lag
Azure SQL Database
- geo-replication
- failover groups
- Only the primary logical server hosts a writable copy of the database
- up to four other logical servers
- We can manually initiate a failover as we notice the problem
- group of databases where data replicates automatically
- from a primary to one or more secondary servers
- automate the response to a failure by defining a policy
replication asynchronous
replication asynchronous
Azure Cosmos DB
multi-regional cloud database system
- Multi-region accounts with multiple write regions
- Multi-region accounts with a single write region
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