f597fc1b07
* Fix languages * Missed change for version number * Add language field for presentation * Revert change in README for double buffer Co-authored-by: Jackie Nim <=>
111 lines
3.4 KiB
Markdown
111 lines
3.4 KiB
Markdown
---
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layout: pattern
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title: Aggregator Microservices
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folder: aggregator-microservices
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permalink: /patterns/aggregator-microservices/
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categories: Architectural
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language: en
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tags:
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- Cloud distributed
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- Decoupling
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- Microservices
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---
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## Intent
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The user makes a single call to the aggregator service, and the aggregator then calls each relevant microservice.
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## Explanation
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Real world example
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> Our web marketplace needs information about products and their current inventory. It makes a call to an aggregator
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> service which in turn calls the product information microservice and product inventory microservice returning the
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> combined information.
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In plain words
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> Aggregator Microservice collects pieces of data from various microservices and returns an aggregate for processing.
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Stack Overflow says
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> Aggregator Microservice invokes multiple services to achieve the functionality required by the application.
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**Programmatic Example**
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Let's start from the data model. Here's our `Product`.
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```java
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public class Product {
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private String title;
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private int productInventories;
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// getters and setters ->
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...
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}
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```
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Next we can introduce our `Aggregator` microservice. It contains clients `ProductInformationClient` and
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`ProductInventoryClient` for calling respective microservices.
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```java
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@RestController
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public class Aggregator {
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@Resource
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private ProductInformationClient informationClient;
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@Resource
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private ProductInventoryClient inventoryClient;
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@RequestMapping(path = "/product", method = RequestMethod.GET)
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public Product getProduct() {
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var product = new Product();
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var productTitle = informationClient.getProductTitle();
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var productInventory = inventoryClient.getProductInventories();
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//Fallback to error message
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product.setTitle(requireNonNullElse(productTitle, "Error: Fetching Product Title Failed"));
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//Fallback to default error inventory
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product.setProductInventories(requireNonNullElse(productInventory, -1));
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return product;
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}
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}
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```
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Here's the essence of information microservice implementation. Inventory microservice is similar, it just returns
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inventory counts.
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```java
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@RestController
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public class InformationController {
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@RequestMapping(value = "/information", method = RequestMethod.GET)
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public String getProductTitle() {
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return "The Product Title.";
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}
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}
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```
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Now calling our `Aggregator` REST API returns the product information.
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```bash
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curl http://localhost:50004/product
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{"title":"The Product Title.","productInventories":5}
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```
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## Class diagram
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## Applicability
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Use the Aggregator Microservices pattern when you need a unified API for various microservices, regardless the client device.
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## Credits
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* [Microservice Design Patterns](http://web.archive.org/web/20190705163602/http://blog.arungupta.me/microservice-design-patterns/)
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* [Microservices Patterns: With examples in Java](https://www.amazon.com/gp/product/1617294543/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=1617294543&linkId=8b4e570267bc5fb8b8189917b461dc60)
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* [Architectural Patterns: Uncover essential patterns in the most indispensable realm of enterprise architecture](https://www.amazon.com/gp/product/B077T7V8RC/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=B077T7V8RC&linkId=c34d204bfe1b277914b420189f09c1a4)
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