Javaone 2016 - Operational Excellence with Hystrix

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Operational Excellence
with Hystrix
Billy Yuen
Principal Engineer
Intuit, Inc.
September 20, 2016
Lesson learned from Quickbooks Online (QBO)

Intuit Mission:
CONSUMERS
SMALL
BUSINESSES
ACCOUNTING
PROFESSIONALS
To improve our customers’ financial lives so profoundly…
they can’t imagine going back to the old way

A Premiere Innovative Growth Company
Employees
8,000+
Customers
45M
Global Offices
US, UK, India,
Canada, Australia
Revenue
4.2B
Founded
1983
Public 1993
INTU

What is resiliency?

Resiliency: Act tough to your enemy even if you are hurting
NORMAL CUSTOMER

And fix the problem quickly before your customers notice!

Why is resiliency hard to achieve?
 Micro-services allow teams to move and innovate faster.
 But failure now will also be distributed!
 New Architecture == New Set of Problems

Even Google has faced this issue!
• On May 3, 2013 “From 6:26 PM to 7:58 PM PT, requests to most Google
APIs resulted in 500 error response messages.”
• “The combination of the bug and configuration error quickly caused all of the serving
threads to be consumed. Traffic was permanently queued waiting for a serving
thread to become available.”
• http://googledevelopers.blogspot.com/2013/05/google-api-infrastructure-
outage_3.html

Challenges we face
• Cascade failures from dependent systems.
• Very few instrumentation and monitoring for the dependent services.
• Decomposition from Monolith to micro-services.
– Design consideration for auto recovery from latency and dependency failure.
– Testing for latency and dependency failure.
• Impossible to achieve 99.9% uptime
– If there are N dependencies and each has 99.9% uptime, best uptime would be 99.9%
^ N (99.9% ^ 10 = 99%).
– If dependency is down for X minutes, our recovery time will be X + Y minutes
(detection and server restart).

How does Hystrix help?
• Also known as “Circuit Breaker”
– Automatic Fail Fast
– Automatic Fail Over (fallback)
– Protocol Agnostics
• Created by an engineer to make his life better during production support!
• Defend against your dependencies (Trust but verify)!
• Battle tested with billions of request per days.
• Metrics Generation

Hystrix at work (fail fast)
Health Check

Overcome Organization Challenge – feature, feature,
feature…
• Growing Pain and Opportunity – QBO experienced big growth and uptime
became a bigger issue.
– Dependency network issue making QBO unresponsive.
– Cascade failure from Disk Failure in one component causing QBO clusters
unresponsive.
• Action over Plan – Implemented Hystrix and monitoring in Payment API to
demonstrate the vision.

Our Journey to implement Hystrix
• Apply Hystrix to legacy code
• Prevent Drift Detection
• Failure Testing
• Real time monitoring
• Production troubleshooting with historical data
• Production support process

Apply Hystrix to Legacy Code
• Challenges
– We don’t know all the network calls. Many calls are also buried in client libraries.
– New Relics can provide the URL for the remote service, but not the stack trace.
• Solution - Hystrix Agent
– Java Agent to detect any “naked” network call.
– Work for both socket and NIO calls.
– https://github.com/Netflix/Hystrix/tree/master/hystrix-contrib/hystrix-network-
auditor-agent

Learning from applying Hystrix Agent in QBO
• Remove Network calls to system that are no longer use.
– Analogous to “Reduce Attack surface” in security.
– Remove unnecessary network calls to “Reduce Dependency Vulnerability”.
• Remove Heart Beat to dependent systems.
• Remove Custom fallback logic.

Prevent Drift detection
• Integrated Hystrix audit agent with regression build.
• Report all unprotected calls in self-service dashboard.

Failure testing
• Mindset changes
– Developer - Coding for resiliency
– Quality - Testing for dependency failure
• Failure testing tools
– Hystrix’s ForceCircuitOpen property
– Unit Test and Integration with Wiremock - Http only
– Custom Proxy (Man in the middle) - Any protocol

Real time monitoring - architecture
• Instance - publish Hystrix Metrics stream (provided by Hystrix).
• Turbine – aggregate all streams in one cluster.

Real time monitoring - dashboard
• Hystrix Dashboard - Rolling window of last ten seconds of dependency
health
• https://github.com/Netflix/Hystrix/tree/master/hystrix-dashboard

Real time monitoring - metrics
• Circuit Breaker Status
• Success, Failure and Timeout Count
• Response time
• Fallback status
• Thread pool status
• https://github.com/Netflix/Hystrix/wiki/Metrics-and-Monitoring

Production troubleshooting with historical data
• Netflix Atlas - https://github.com/Netflix/atlas/wiki/Overview
• Intuit – export the Hystrix Metrics to Splunk
– Pinpoint production issue root cause.
– Measurement for actual latency (Network + Service).
– Troubleshoot random “blip”. What is “blip”?

Splunk Hystrix Dashboard
• Aggregate data by any timeframe
• Drill down to specific Hystrix command for detail.

Production support process
• Configure Alerts around critical Hystrix Commands in Splunk
• Integrate Alerts with PagerDuty.
• Use Hystrix Dashboard to review real time system health.
• Use Splunk to debug production issues
Alert Page Revie
w
Debu
g

Other Considerations
• Is the call necessary?
• Can you create fallback for read?
• Client does not need to know it is from fallback (except fragment caching)
• Can you handle offline write?
• Idempotence for write (or verify before calling again)
• Limit blast radius with thread pool or semaphore.
• Adjust the Hystrix default parameter to your use case.
• Fallback needs to be fast and highly available.
• Timeout vs Failure
• Not applicable to stream or batch.

Thread pool vs Semaphore
• Thread pool
– Guaranteed timeout by using thread interrupt.
– More memory required.
– Support Concurrent programming (Future is non-blocking).
• Semaphore
– No timeout guarantee (your code will assume the timeout responsibility).
– Set Hystrix Timeout to be greater than your timeout to avoid false timeout.
– Should throw HystrixTimeoutException if client code throws timeout exception.
– Scale better for large pool.

E2E experience including UI
• Focus on critical workflows!
• QBO
– Provide degraded experience if not available.
• Payroll is down
• Invoice without attachment service.
– Allow Login if subscription service is temporary not available.
• Payments Service
– Limit dependency calls to only applicable use case.
– Cache read-only data with last known good value.

Demo
• HystrixCommand
– Synchronous
– Asynchronous
– Reactive
– Thread pool vs Semaphore
• HystrixObservableCommand for NIO
• Callable Wrapper for TLS
• Logging Metrics
• https://github.com/billyy/Hystrix-Tutorial

Implementation Best Practices
• Don’t implement fallback if you don’t have a fallback.
• Don’t call another Hystrix Command from catch.
• Good and Bad use of fallback.
• Throw Hystrix TimeoutException if your code is doing timeout.
• Update your catch block once you have implemented Hystrix.
• Avoid the use of thread local.
• Retry only if necessary.

Don’t implement fallback if you don’t have a fallback

Don’t call another Hystrix Command from catch

Good use of fallback

Bad use of fallback

Throw Hystrix TimeoutException if your code is doing
timeout
• Hystrix will report all exceptions as failure.
• Timeout will indicate a potential issue with dependency instead of coding
issue.
• Need to configure Hystrix timeout > your timeout.

Update your catch block once you have implemented Hystrix

Retry only if necessary
• Hystrix does NOT support retry.
• Retry code inside Hystrix Command will skew your metrics.
• Bad things can happen
– Good chance that the immediate retry could also timeout.
– Overload the dependency.
– Exceed your SLA.
• If you have to retry, implement the retry outside of Hystrix.

Minimize the use of thread local
• Not explicit to the caller.
• TLS needs to be copied to the Hystrix worker thread and reset afterward
(Prone for error).
• Implement callable wrapper if TLS is required.
• https://github.com/Netflix/Hystrix/issues/92

Important differences in Hystrix version
• 1.2.x
– Initial public release.
• 1.3.x
– Add support for RxJava.
– Semaphore based execution cannot be interrupted but would throw exception if SLA
is exceeded (even if the call is successful!).
• 1.4.x
– Add HystrixObservableCommand for NIO.
– Semaphore based execution can be interrupted by a separate background thread.
– HystrixTimeoutException is public (1.4.18+).
• 1.5.x – Re-architecture of the Metrics to support metric streaming.

Different ways to implement Hystrix
• Client library - Hystrix jar
– http://www.slideshare.net/MattJacobs11/using-hystrix-to-build-resilient-distributed-
systems-58836753
• Existing application – Javanica
– https://github.com/Netflix/Hystrix/tree/master/hystrix-contrib/hystrix-javanica
• New application - Spring Cloud
– http://cloud.spring.io/spring-cloud-netflix/spring-cloud-netflix.html

Thanks!!!
billy_yuen@intuit.com
Confidential – Oracle Internal/Restricted/Highly Restricted 40

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