A lot has changed - Memory, Storage, and CPU are cheaper and available on demand. Cloud technologies have also disrupted this domain; we now have Infrastructure as a Service (IaaS) - Scaling, Load Balancing, and DR responsibilities have been delegated to the Cloud service providers. By Giri Venkatesan.
In an ideal world, a messaging broker would never need to open the payload - it can be simply passing messages between producers and consumers based on subscription. Not all consumers are equal; they may be built to handle subsets of messages even if they are of the same class. For example, a Tax Calculation service would need to process the message differently based on the country or region the message is originating from.
Fortunately, MQTT-based brokers adopted the hierarchical representation of topics from the get-go.
Source: https://www.linkedin.com/pulse/message-routing-topics-thought-shift-giri-venkatesan/
The benefits of such a hierarchical scheme don’t stop there. Now we can use wild cards at any level to capture a broader range of message topics in a subscription:
- Single-level wildcard: ‘*’
- All credit card transactions from store 1049, with transaction number beginning ‘4’
quickpay/credit/*/4*/01049
- Multi-level wildcard: ‘>’
- All debit transaction to be cleared at bank 18
quickpay/debit/0018/>- Literals at each level are treated as Strings - hence wildcard usage on data types like latitude/longitude coordinates and other custom identifiers would also benefit
bustrak/gps_updt/*/*/45.3*/-75.7*
With support for versioning, topics can be altered dynamically without affecting the existing subscribers and overall architecture. Good read!
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