我们突然开始在应用程序服务中收到以下错误，我们最近没有对配置进行任何更改。任何人都可以提供一些有关错误的信息吗？
Caused by: com.netflix.hystrix.exception.HystrixRuntimeException: xxx service could not be queued for execution and no fallback available.
Caused by: java.util.concurrent.RejectedExecutionException: Rejected command because thread-pool queueSize is at rejection threshold.
网关中的配置为：
hystrix.command.default.execution.isolation.strategy=THREAD
hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=360000
hystrix.threadpool.default.coreSize=40
hystrix.command.default.circuitBreaker.forceClosed=true
hystrix.threadpool.default.maxQueueSize=2000
hystrix.threadpool.default.queueSizeRejectionThreshold=1800
zuul.routes.<instance>.path=/<instance>/**
zuul.routes.<instance>.serviceId=<instance>
zuul.routes.<instance>.sensitiveHeaders=
<instance>.ribbon.OkToRetryOnAllOperations=true
<instance>.ribbon.MaxAutoRetriesNextServer=1
<instance>.ribbon.MaxAutoRetries=0
hystrix.command.<instance>.execution.isolation.strategy=THREAD
hystrix.command.<instance>.execution.isolation.thread.timeoutInMilliseconds=360000
hystrix.threadpool.<instance>.coreSize=40
hystrix.command.<instance>.circuitBreaker.forceClosed=true
hystrix.threadpool.<instance>.maximumSize=100
hystrix.threadpool.<instance>.queueSizeRejectionThreshold=80
我们将 coreSize、forceClosed、maxQueueSize 和 quoteSizeRejectionThreshold 作为默认设置，但并未配置此级别。它仍然存在问题。我们尝试重新启动 Gateway 和 Eureka 实例。