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![32 VictorRentea.ro
An operaEon is idempotent if repeaEng it doesn't change any state
§Get product by id via GET ?
- ✅ YES: no state changes on server
§Cancel Payment by id via HTTP DELETE or message
- ✅ YES: canceling it again won't change anything
§Update Product price by id via PUT or message
- ✅ YES: the price stays unchanged on server
§Place Order { items: [..] } via POST or message
- ❌ NO the retry could create a second order
- ✅ YES, detect duplicates via pastHourOrders = Map<customerId, List<hash(order)>>
§Place Order { id: UUID, items: [..] } (client generated id) via PUT or message
- ✅ YES: a duplicate would cause a PK/UK viola>on
Idempotency](https://image.slidesharecdn.com/resiliencepatternsvoxxedcern-240123072957-b7aaf4a2/85/Microservice-Resilience-Patterns-VoxxedCern-24-32-320.jpg)
Uploaded byVictor Rentea
Microservice Resilience Patterns @VoxxedCern'24
The document discusses resilience patterns for microservices, emphasizing the importance of handling unexpected situations with minimal user impact and graceful degradation. It outlines various strategies including isolation, bulkheads, circuit breakers, and idempotency that help maintain system availability and performance under failure conditions. The author, Victor Rentea, also highlights the significance of monitoring, asynchronous communication, and eventual consistency in building resilient systems.
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Microservice Resilience Patterns @VoxxedCern'24
- 1. The Resilience Patterns yourMicroservices Teams Should Know Victor Rentea | https://victorrentea.ro | @victorrentea
- 2. 👉 victorrentea.ro/training-offer VictorRentea.ro 👋 I'mVictor Rentea 🇷🇴 PhD(CS), Java Champion 18 years of code 10 years training bright developers at 120+ EU companies: ❤ Clean Code, Tes+ng, Architecture 🛠 Java, Spring, Hibernate, Reac+ve ⚡ Java Performance, Secure Coding Educa9ve Talks on YouTube.com/vrentea European So=ware Cra=ers Community (6K devs) 👉 Join for free monthly events at victorrentea.ro/community Life += 👪 + 🐈 + 🌷garden
- 3. 3 VictorRentea.ro Benefits ofMicroservices ü Faster Time-to-Market: 😁 Business ü Lower Cognitive Load: 😁 Developers ü Technology Upgrade/Change ü Scalability for the 🔥hot parts that require it ü Availability, tolerance to partial failures
- 4. 4 VictorRentea.ro But we'resafe. We're using HTTP between our services. 😎
- 5. 5 VictorRentea.ro Fallacies ofDistributed Computing The network is reliable Latency is zero Bandwidth is infinite Transport cost is zero The network is secure Fixed topology Has one administrator The network is homogeneous
- 6. 6 VictorRentea.ro A distributedsystem is one in which the failure of a computer you didn't even know existed can render your own computer unusable. Leslie Lamport
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- 9. 9 VictorRentea.ro = 𝑀𝑇𝑇𝐹 𝑀𝑇𝑇𝐹 +𝑀𝑇𝑇𝑅 Mean Time To Failure (crash) Mean Time To Recovery (downtime) ⬆ Write more tests: unit-, integration-, smoke-, end-to-end- Also: load-, spike-, resilience- (see ToxyProxy by shopify) ⬆ ⬇ Faster Recovery 𝐴𝑣𝑎𝑖𝑙𝑎𝑏𝑖𝑙𝑖𝑡𝑦
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- 11. 11 VictorRentea.ro The abilityof a system to handle unexpected situations - without users noticing it (best case), or - with a graceful degradation of service Resilience
- 12. 12 VictorRentea.ro 👉 AQuery reading data can failover to: - Return an older value, eg. cached 5 minutes ago - Return a lower quality response: eg. NETFLIX: per-country, not client-tailored >tles - Call a slower system: eg. search in SQL DB when ES is down - Send results later: "We'll email you the results when done" 👉 A Command changing data: - Outbox table paJern: insert it in DB + schedule⏱ a persistent retry - Send it as a message instead of HTTP - Log an error raising an alarm🔔 calling for manual interven+on - Send an error event to a supervisor for automa+c recovery ("saga" paNern) Graceful Degrada5on
- 13. 13 VictorRentea.ro ISOLATION LOOSE COUPLING LATENCYCONTROL SUPERVISION
- 14. 14 VictorRentea.ro The enKresystem becomes unavailable ↓ Split the system in separate pieces and isolate those pieces against each other. Catastrophic Failure
- 15. 15 VictorRentea.ro §Long chainsof REST calls A à B à C à D à E §A request causes the instance to restart & client keeps retrying §A "poison pill" message is retried infinitely, blocking the listener §Unbounded queues kept in memory causes OutOfMemoryError §Concurrent massive import/export overloads the DB ☠ Isola7on An7-Pa;erns ☠
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- 18. 18 VictorRentea.ro Bulkhead Isolated Failure Theship does not sink! 🎉
- 19. 19 VictorRentea.ro §Core isolaKonpaVern §Pure design issue: What should be independent of what ? §Used as units of redundancy §Used as units of scale Bulkhead (aka Failure Units) Microservices Resilience Pa/erns by jRebel
- 20. 20 VictorRentea.ro §Key Features:catalog, search, checkout §Markets / Regions §Tenants ☁ Isolate them using separate: §ConnecKon-/ Thread- Pools §ApplicaKon Instances §Databases, Queues Bulkhead Examples
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- 22. 22 VictorRentea.ro §Limit theload on a server to - 💥 Prevent a crash: a few 503 are beNer than OutOfMemoryError - ⏱ Preserve response +me: error is beNer than OK aTer 60 seconds - ⚠ Protect cri+cal endpoints: place order over export invoices - ⚖ Ensure fairness: return 429 to greedy clients/tenants - 💲 Limit auto-scaling to fit budget §What to throEle: - Request Rate: max 300 requests/second, eg via @RateLimiter - Concurrency: max 3 exports in parallel, eg via @BulkHead - Traffic: max 1 GB/minute, or cost: max 300 credits/minute Thro=ling
- 23. 23 VictorRentea.ro C degraded BthroNled (stopped) A untouched as it's cri>cal Thro%ling Features
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- 25. 25 VictorRentea.ro Sweet Spot ßbest performance à Performance Response Curve throughput # requests completed / sec by one machine # concurrent requests - load Enqueuing excess load can improve overall performance response_time = queue_waiting + execution_time Monitored. Bounded. 💥
- 26. 26 VictorRentea.ro §Obvious, yetoen neglected §Validate data when you see it: client requests & API responses §But don't go too far: validate only what you care about👉 Full Parameter Check
- 27. 27 VictorRentea.ro Be conservativein what you do, but liberal in what you accept from others. -- Robustness Principle (aka Postel's Law)
- 28. 28 VictorRentea.ro ISOLATION LOOSE COUPLING LATENCYCONTROL SUPERVISION Thro%ling Bulkhead Complete Parameter Checking Bounded Queues
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- 30. 30 VictorRentea.ro §Set aKmeout every Kme you block👍 §If too large - Impacts my response >me - ⚠ Mind the defaults: RestTemplate=1 minute, WebClient=unbounded😱 §If too short - False errors: the opera>on might succeed later on the server - Keep above the API measured/SLA response >me (max or 99%th) - Tailor per endpoint, eg: longer for /export §Monitoring + Alarms🔔 Timeout
- 31. 31 VictorRentea.ro A callfailed or ,med out > I want to retry it. Key ques,ons to ask?🤔 Error cause: 400, 500, Kmeout, {retryable:false} in response?.. Worth retrying? Max aVempts? What backoff? How to monitor? Is the operaKon idempotent?
- 32. 32 VictorRentea.ro An operaEonis idempotent if repeaEng it doesn't change any state §Get product by id via GET ? - ✅ YES: no state changes on server §Cancel Payment by id via HTTP DELETE or message - ✅ YES: canceling it again won't change anything §Update Product price by id via PUT or message - ✅ YES: the price stays unchanged on server §Place Order { items: [..] } via POST or message - ❌ NO the retry could create a second order - ✅ YES, detect duplicates via pastHourOrders = Map<customerId, List<hash(order)>> §Place Order { id: UUID, items: [..] } (client generated id) via PUT or message - ✅ YES: a duplicate would cause a PK/UK viola>on Idempotency
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- 34. 34 VictorRentea.ro Over thelast 5 minutes, 99% requests to a system failed or timed-out. What are the chances a new call will succeed?
- 35. 35 VictorRentea.ro If youknow you're going to fail, at least fail fast.
- 36. 36 VictorRentea.ro Circuit Breaker 🛑OPEN ✅ CLOSED 🛑 OPEN = flow is stopped Introduced by Michael Nygard in his book Release It h"ps://www.amazon.com/Release-Produc7on-Ready-So:ware-Pragma7c-Programmers/dp/0978739213
- 37. 37 VictorRentea.ro Circuit Breaker ✅CLOSED allow all calls, coun;ng OK, errors, ;med-out 🛑 OPEN stop all calls for a while 🟡 HALF-OPEN allow only a few calls (eg: 2), to test if server is back any request failed ⏱ delay all requests=OK failed % > threshold (eg. >99%) over last 100 calls/seconds START Fail fast to save client resources. Let server recover. Hit server gently aTer recovery.
- 38. 38 VictorRentea.ro §When callinga fragile/slow systems: SAP, Siebel, external API §Between services in different bulkheads §At API Gateway level (entry point to ecosystem) Where to Implement These? Timeout Retry Circuit Breaker ThroYling Fallback
- 39. 39 VictorRentea.ro Bounded Queues ISOLATION LOOSE COUPLING LATENCYCONTROL SUPERVISION Fan out & quickest reply Retry Circuit Breaker Timeouts Fail Fast Thro%ling Bulkhead Complete Parameter Checking Idempotency SLA
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- 41. 41 VictorRentea.ro §Keeping stateinside a service can impact: - Consistency: all nodes must sync it - Availability: failover nodes must replicate it - Scalability: new instances must copy it §Move state out 👍 - To databases - To clients (browser, mobile) if related to UI flow - Via request tokens if user metadata (email, roles..) Stateless Service
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- 43. 43 VictorRentea.ro §Guaranteed delivery,even if the receiver is unavailable now §Prevent cascading failures between bulkheads §Breaks the call stack paradigm -- thus, apparently hard §With resilience concerns, REST also becomes scary §Sender should NOT need a response or status – design change §DON'T expect that your changes are applied instantaneously è Eventual Consistency ç Asynchronous Communica,on (MQ)
- 44. 44 VictorRentea.ro You caneither be Consistent or Available when Partitioned CAP Theorem All data is in perfect sync You get an answer Using mulEple machines
- 45. 45 VictorRentea.ro §Examples: - Oneof the items in stock is accidentally broken during handling - The product page displays stock: 1, but by the Eme the customer clicks "add to cart", someone else already bought it! è Relax, and embrace Eventual Consistency - A"er you understand the busine$$ impact The Real World is not Consistent
- 46. 46 VictorRentea.ro §State movesvia events à less REST J §Lossless capture of history §Ability to =me-travel by replaying events §Allows scaling up the read flows separately (CQRS) Event-Sourcing
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- 48. 48 VictorRentea.ro §Poison pillmessage è send to dead-leEer or retry queue §Duplicated messages è idempotent consumer §Out-of-order messages è aggregator, Kme-based- on smart- §Data privacy è Claim Check paVern §Event versioning è Backward-forward compaPbilty §MisconfiguraKon of infrastructure Messaging PiIalls
- 49. 49 VictorRentea.ro Bounded Queues ISOLATION LOOSE COUPLING LATENCYCONTROL SUPERVISION Fan out & quickest reply Retry Circuit Breaker Timeouts Fail Fast Thro%ling Bulkhead Complete Parameter Checking Error Handler Asynchronous Communica;on Loca;on Transparency Idempotency Event-Driven Stateless Eventual Consistency Monitor Escala;on SLA Also see: "Pa:erns of resilience" talk by Uwe Friedrichsen Health Check
- 50. 50 VictorRentea.ro Clients cannot/ should not handle downstream errors
- 51. 51 VictorRentea.ro People No matterwhat a problem seems to be at first, it's always a people problem. - First Law of Consulting
- 52. 52 VictorRentea.ro To buildhighly-resilient systems, you need DevOps teams
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- 55. 55 VictorRentea.ro Own YourProduc8on See metrics & set alarms Prometheus+Grafana.. Distributed request tracing OpenTelemetry Log aggregaPon ELK... Time span samples Zipkin... SHOW STOPPER if lacking these
- 56. 56 VictorRentea.ro §IdenKfy bulkheads(failure units) §Sync calls += Kmeout, retry, throVling, circuit breaker, failover §Slow responses can cause cascading failures §Slow down to move faster §If you fail, at least fail fast §Embrace eventual consistency and favor async messages Key Points
- 57. The Resilience Patterns yourMicroservices Teams Should Know Victor Rentea | https://victorrentea.ro | @victorrentea Thank you! Join my community: