Coordinating non blocking io melb-clj
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This document discusses various approaches to coordinating asynchronous HTTP requests and non-blocking I/O in a web application built with Clojure and HttpKit. It presents several solutions using promises and monads to handle asynchronous operations like making a payment on a bill by first retrieving a credit card token, then making a payment, and finally retrieving updated bill details. The solutions range from synchronous code to fully asynchronous approaches using raw promises, promise monads, and chained promises.
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Coordinating non blocking io melb-clj
- 1. COORDINATING NON-BLOCKING IO AND ASYNC HTTP RESPONSES
- 3. WHAT IS THE WEB STACK • • • HttpKit as web server Compojure for routing HttpKit for non-blocking http requests
- 4. REACTIVE APPROACH PREFERRED We are not using either Functional Reactive Programming or Reactive Programming libraries. Eg. Rx.java • May satisfy other more broad definitions of reactive • Are making better use of threads than traditional approaches •
- 5. Make a payment on a bill - Not necessarily a full payment ! POST /bills/:bill-id/payments Session: user-id Post Data: amount ! 1. Get credit card token for user 1.1. Send request to payment gateway 2. Find how much was left to be payed ! If payment is success: render amount remaining on bill If payment fails: render error
- 6. CANDIDATES • Synchronous promises • core.async • Promise monad let/do • Lamina • Promise monad chain/lift- • Meltdown m-2 pipeline (LMAX Disrupter) • Raw promises • Pulsar promises • Raw callbacks • Pulsar Actors
- 7. SOLUTION 0: SYNCHRONOUS (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (let [token (auth/card-‐token user-‐id) details (bill/details bill-‐id) transaction (payment/bill bill-‐id amount @token)] (if (success? @transaction) (render-‐remaining-‐response @details amount) error-‐response)))
- 8. SOLUTION 1: PROMISE MONAD LET/DO (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (let [token-‐req (auth/card-‐token user-‐id) details-‐req (bill/details bill-‐id)] (do [token token-‐req transaction (payment/bill bill-‐id amount token) details details-‐req] (return (if (success? transaction) (render-‐remaining-‐response details amount) error-‐response)))))
- 9. SOLUTION 1.1: PROMISE MONAD LET/DO/DO (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (let [token-‐req (auth/card-‐token user-‐id) details-‐req (bill/details bill-‐id)] (do [token token-‐req transaction (payment/bill bill-‐id amount token)] (if (success? transaction) (do [details details-‐req] (return (render-‐remaining-‐response details amount))) (return error-‐response)))))
- 10. SOLUTION 1.2: PROMISE MONAD DO (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (do [token (auth/card-‐token user-‐id) transaction (payment/bill bill-‐id amount token) details (bill/details bill-‐id)] (return (if (success? transaction) (render-‐remaining-‐response details amount) error-‐response))))
- 11. SOLUTION 1.3: PROMISE + ERROR MONADS (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (do [token (auth/card-‐token user-‐id) transaction (payment/bill bill-‐id amount token) details (bill/details bill-‐id)] (return (render-‐remaining-‐response details amount))))
- 12. SOLUTION 2: PROMISE CHAIN AND LIFT-M-2 (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (let [transaction-‐req (chain (promise user-‐id) auth/card-‐token (partial payment/bill bill-‐id amount)) details-‐req (bill/details bill-‐id)] (lift-‐m-‐2 (fn [transaction details] (if (success? transaction) (render-‐remaining-‐response details amount) error-‐response))) transaction-‐req details-‐req))
- 13. SOLUTION 3: RAW PROMISES (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (let [transaction-‐req (-‐> (auth/card-‐token user-‐id) (then (partial payment/bill bill-‐id amount))) details-‐req (bill/details bill-‐id)] (when transaction-‐req details-‐req (fn [transaction details] (if (success? transaction) (render-‐remaining-‐response details amount) error-‐response)))))
- 14. SOLUTION 4: RAW CALLBACKS Not Viable
- 15. SOLUTION 5: CORE.ASYNC (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (go (let [token (auth/card-‐token user-‐id) details (bill/details bill-‐id) transaction (payment/bill bill-‐id amount (<! token))] (if (success? (<! transaction)) (render-‐remaining-‐response (<! details) amount) error-‐response))))
- 16. SOLUTION 6: LAMINA PIPELINE (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (let [details-‐req (bill/details bill-‐id)] (pipeline (auth/card-‐token user-‐id) (partial payment/bill bill-‐id amount) (fn [transaction] (if (success? transaction) (on-‐realized details-‐req (fn [details] (render-‐remaining-‐response details amount))) error-‐response)))))
- 18. SOLUTION 8: PULSAR PROMISES (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] #(let [token (auth-‐card-‐token user-‐id) details (bill-‐details bill-‐id) transaction (payment-‐bill bill-‐id amount @token)] (if (success? @transaction) (render-‐remaining-‐response @details amount) error-‐response)))
- 19. SOLUTION 9: PULSAR ACTORS Not Appropriate
- 20. (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (let [token (auth/card-‐token user-‐id) details (bill/details bill-‐id) transaction (payment/bill bill-‐id amount @token)] (if (success? @transaction) (render-‐remaining-‐response @details amount) error-‐response))) Synchronous (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] (go (let [token (auth/card-‐token user-‐id) details (bill/details bill-‐id) transaction (payment/bill bill-‐id amount (<! token))] (if (success? (<! transaction)) (render-‐remaining-‐response (<! details) amount) error-‐response)))) core.async (GET "/bills/:bill-‐id/payments" [bill-‐id user-‐id amount] #(let [token (auth-‐card-‐token user-‐id) details (bill-‐details bill-‐id) transaction (payment-‐bill bill-‐id amount @token)] (if (success? @transaction) (render-‐remaining-‐response @details amount) (error-‐response)))) Pulsar
- 21. SCALA def payBill(billId: Integer, userId: Integer, amount: Integer):Future[Option[Json]] = { val seq = for { token <-‐ Auth.cardToken(userId) tr <-‐ Payment.bill(token) } yield tr async { val transactionProcess = await(seq.run) val detailProcess = await(BillOps.details(billId)) for { transaction <-‐ transactionProcess detail <-‐ detailProcess } yield renderRemainingResponse(amount, detail) } }
- 23. HELLO WORLD • Single C1-Medium • 7GB •8 Ram Cores • 313,852 Concurrent Users • 4756.79 Requests Per Second • More meaningful results once in SVT with full implementation
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