A RESTful Approach to Real-time, Event Driven Messaging by Paul O'Fallon

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A RESTful Approach to Real-time, Event Driven Messaging Paul O’Fallon @paulofallon Enterprise Architect, Cox Automotive

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4 Our Starting Point

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5 Drawbacks • Adding JMS consumers required SOA configuration changes • JMS isn't the best for non-JVM language support • JMS isn't the best for integrating with 3rd parties over the Internet • No message history • No symmetry between SOAP services and JMS messages

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6 A new "Manheim API" Consistent, cohesive set of endpoints RESTful, hypermedia-inspired API Self-service sign-up, API key management Support for internal projects, customers and partners OAuth2 support for delegated interactions

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7 Each resource has an “href” GET https://api.manheim.com/units/id/429a5d00-353c... {  "href": "https://api.manheim.com/units/id/429a5d00-353c...",  "vin": "1G1AP14P577112297",  "description": {  "modelYear": 2014,  "make": "Ford",  "model": "Mustang",  "trim": "GT Convertible 2-Door",  // ...  }

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8 Related Resources are also “hrefs” GET https://api.manheim.com/consignments/id/863cd3c0... {  "href": "https://api.manheim.com/consignments/id/863cd3c0...",  "status": "ACTIVE", "unit": {  "href": "https://api.manheim.com/units/id/429a5d00-353c..."  },  "operatingLocation": {  "href": "https://api.manheim.com/locations/id/AAA"  },    // ...  }

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10 Eventer

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11 Events “Just an href”

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12 API Example: /events POST https://api.manheim.com/events {  "resource": "https://api.manheim.com/consignments/id/863cd3c0...", "eventType": "CONSIGNMENTS.CHECKEDIN",  "body": {  "href": "https://api.manheim.com/consignments/id/863cd3c0...",  "status": "ATAUCTION",  "unit": {  "href": "https://api.manheim.com/units/id/429a5d00-353c..."  },  "operatingLocation": {  "href": "https://api.manheim.com/locations/id/AAA"  }  }  }

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13 Eventer

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14 Eventer

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15 Subscribers & Subscriptions

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16 API Example: /subscribers POST https://api.manheim.com/subscribers { "callback": "http://www.somecustomer.com/cb", "headers": { "Authorization": "Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==" }, "email": "jdoe@somecustomer.com" } Location: https://api.manheim.com/subscribers/id/005739ae-625b...

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17 Subscribers & Subscriptions

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18 Subscription Matching Criteria • One or more Resource URLs (inc. related resources) • Event type (inc. wildcards: CONSIGNMENTS.*) • VIN … or any combination of the above (treated as a logical 'and')

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19 Resource Expansion { "resource": "https://api.manheim.com/consignments/id/863cd3c...",  "eventType": "CONSIGNMENTS.CHECKEDIN", "body": {  "href": "...",  "status": "ATAUCTION",  "unit": {  "href": "..."  },  "operatingLocation": {  "href": "..." }  } } "expansions": [  "root", "unit",  "operatingLocation"  ]

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20 API Example: /subscriptions POST https://api.manheim.com/subscriptions { "subscriber": {  "href": "https://api.manheim.com/subscribers/id/005739ae..."  }, "criteria": [  { "type": { "pattern": "CONSIGNMENTS.CHECKEDIN" } }, { "resource": { "href": "https://api.manheim.com/locations/id/AAA" } } ], "expansions": ["root", "unit"] }

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21 A Published Event { "href": "https://api.manheim.com/events/id/624c277c...", "eventType": "CONSIGNMENTS.CHECKEDIN", "body": { "href": "https://api.manheim.com/consignments/id/863cd3c0...", "status": "ATAUCTION", "operatingLocation": { "href": https://api.manheim.com/locations/id/AAA } }, "createdOn": "2015-11-16T20:48:26.138Z", "subscription": { "href": "https://api.manheim.com/subscriptions/id/cd09a47c..." }, "subscriber": { "href": "https://api.manheim.com/subscribers/id/005739ae..." } }

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22 Can Pull Events Too By subscription  https://api.manheim.com/events/subscription/696f2d67-b483… By subscriber  https://api.manheim.com/events/subscriber/005739ae-625b... Individual event https://api.manheim.com/events/id/1c160532-13ac...

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23 High Level Architecture

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24 Future Plans Today: Recovery via Retrieval 1. When retries are exhausted, event is not passed to the callback 2. Client must pull (GET /events) for missing events to fill in gaps Future: Recovery via Replay 1. Client can pause callbacks, or… 2. Client can request a "replay" of missed events 3. Recovered events will be delivered in order (before new events)