Zuul defaulting hystrix isolation strategy to SEMAPHORE - spring-cloud

Question

This is in continuation to my previous question where in my hystrix dashboard the Thread Pool section keeps on loading:- Hystrix Dashboard with Turbine issue
Why is zuul forcing the isolation strategy for hystrix to be SEMAPHORE. I tried adding the configuration to my application.yml but still it ignores that and uses SEMAPHORE. Is there something that I am missing here. Or how would i change it from SEMAPHORE to THREAD.
Application.yml
info:
component: Zuul Server
eureka:
client:
service-url:
defaultZone: http://localhost:8761/eureka/
endpoints:
restart:
enabled: true
shutdown:
enabled: true
health:
sensitive: false
server:
port: 8006
zuul:
routes:
UserCards-V1:
path: /user/v1/accountholders/*/cards/**
service-id: usercards-v1
strip-prefix: false
UserTransactions-V1_1:
path: /user/v1/accountholders/*/transactions
service-id: usertransactions-v1
strip-prefix: false
UserTransactions-V1_2:
path: /user/v1/accountholders/*/accounts/*/transactions
service-id: usertransactions-v1
strip-prefix: false
UserAccounts-V1:
path: /user/v1/accountholders/*/accounts/**
service-id: useraccounts-v1
strip-prefix: false
UserCardholders-V1:
path: /user/v1/accountholders/**
service-id: usercardholders-v1
strip-prefix: false
hystrix:
command.default.execution.isolation.strategy: THREAD
command.default.execution.isolation.thread.timeoutInMilliseconds: 60000
command.default.execution.timeout.enabled: false
command.default.fallback.enabled: false
threadpool.default.coreSize: 20
ribbon:
ConnectTimeout: 3000
ReadTimeout: 60000
turbine:
clusterNameExpression: zuul
Hystrix.stream
data: {"type":"HystrixCommand","name":"usercardholders-v1RibbonCommand","group":"RibbonCommand","currentTime":1451411772021,"isCircuitBreakerOpen":false,"errorPercentage":0,"errorCount":0,"requestCount":0,"rollingCountBadRequests":0,"rollingCountCollapsedRequests":0,"rollingCountEmit":0,"rollingCountExceptionsThrown":0,"rollingCountFailure":0,"rollingCountEmit":0,"rollingCountFallbackFailure":0,"rollingCountFallbackRejection":0,"rollingCountFallbackSuccess":0,"rollingCountResponsesFromCache":0,"rollingCountSemaphoreRejected":0,"rollingCountShortCircuited":0,"rollingCountSuccess":0,"rollingCountThreadPoolRejected":0,"rollingCountTimeout":0,"currentConcurrentExecutionCount":0,"rollingMaxConcurrentExecutionCount":0,"latencyExecute_mean":0,"latencyExecute":{"0":0,"25":0,"50":0,"75":0,"90":0,"95":0,"99":0,"99.5":0,"100":0},"latencyTotal_mean":0,"latencyTotal":{"0":0,"25":0,"50":0,"75":0,"90":0,"95":0,"99":0,"99.5":0,"100":0},"propertyValue_circuitBreakerRequestVolumeThreshold":20,"propertyValue_circuitBreakerSleepWindowInMilliseconds":5000,"propertyValue_circuitBreakerErrorThresholdPercentage":50,"propertyValue_circuitBreakerForceOpen":false,"propertyValue_circuitBreakerForceClosed":false,"propertyValue_circuitBreakerEnabled":true,"propertyValue_executionIsolationStrategy":"SEMAPHORE","propertyValue_executionIsolationThreadTimeoutInMilliseconds":60000,"propertyValue_executionTimeoutInMilliseconds":60000,"propertyValue_executionIsolationThreadInterruptOnTimeout":true,"propertyValue_executionIsolationThreadPoolKeyOverride":null,"propertyValue_executionIsolationSemaphoreMaxConcurrentRequests":100,"propertyValue_fallbackIsolationSemaphoreMaxConcurrentRequests":10,"propertyValue_metricsRollingStatisticalWindowInMilliseconds":10000,"propertyValue_requestCacheEnabled":true,"propertyValue_requestLogEnabled":true,"reportingHosts":1,"threadPool":"RibbonCommand"}
data: {"type":"HystrixCommand","name":"usercards-v1RibbonCommand","group":"RibbonCommand","currentTime":1451411772522,"isCircuitBreakerOpen":false,"errorPercentage":0,"errorCount":0,"requestCount":1,"rollingCountBadRequests":0,"rollingCountCollapsedRequests":0,"rollingCountEmit":0,"rollingCountExceptionsThrown":0,"rollingCountFailure":0,"rollingCountEmit":0,"rollingCountFallbackFailure":0,"rollingCountFallbackRejection":0,"rollingCountFallbackSuccess":0,"rollingCountResponsesFromCache":0,"rollingCountSemaphoreRejected":0,"rollingCountShortCircuited":0,"rollingCountSuccess":1,"rollingCountThreadPoolRejected":0,"rollingCountTimeout":0,"currentConcurrentExecutionCount":0,"rollingMaxConcurrentExecutionCount":1,"latencyExecute_mean":0,"latencyExecute":{"0":0,"25":0,"50":0,"75":0,"90":0,"95":0,"99":0,"99.5":0,"100":0},"latencyTotal_mean":0,"latencyTotal":{"0":0,"25":0,"50":0,"75":0,"90":0,"95":0,"99":0,"99.5":0,"100":0},"propertyValue_circuitBreakerRequestVolumeThreshold":20,"propertyValue_circuitBreakerSleepWindowInMilliseconds":5000,"propertyValue_circuitBreakerErrorThresholdPercentage":50,"propertyValue_circuitBreakerForceOpen":false,"propertyValue_circuitBreakerForceClosed":false,"propertyValue_circuitBreakerEnabled":true,"propertyValue_executionIsolationStrategy":"SEMAPHORE","propertyValue_executionIsolationThreadTimeoutInMilliseconds":60000,"propertyValue_executionTimeoutInMilliseconds":60000,"propertyValue_executionIsolationThreadInterruptOnTimeout":true,"propertyValue_executionIsolationThreadPoolKeyOverride":null,"propertyValue_executionIsolationSemaphoreMaxConcurrentRequests":100,"propertyValue_fallbackIsolationSemaphoreMaxConcurrentRequests":10,"propertyValue_metricsRollingStatisticalWindowInMilliseconds":10000,"propertyValue_requestCacheEnabled":true,"propertyValue_requestLogEnabled":true,"reportingHosts":1,"threadPool":"RibbonCommand"}

Answer 1

zuul.ribbonIsolationStrategy=THREAD
You can use above command to force the ZUUL to use the THREAD strategy

Answer 2

Why is zuul forcing the isolation strategy for hystrix to be SEMAPHORE
See https://github.com/spring-cloud/spring-cloud-netflix/blob/f3deb04521c8c0a0b6d9923b0b37d8673cb7fa0b/spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/route/support/AbstractRibbonCommand.java#L85.
// we want to default to semaphore-isolation since this wraps
// 2 others commands that are already thread isolated