title: java.util.concurrent.RejectedExecutionException: Rejected command because thread-pool queueSize is at rejection threshold
body: <p>We suddenly started receiving following error in out application services, we did not make any change to config in recent time.  Could any one provide some information regarding error?</p>
  
  <pre><code>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.
  </code></pre>
  
  <p>Configuration in gateway are:</p>
  
  <pre><code>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.&lt;instance&gt;.path=/&lt;instance&gt;/**
  zuul.routes.&lt;instance&gt;.serviceId=&lt;instance&gt;
  zuul.routes.&lt;instance&gt;.sensitiveHeaders=
  &lt;instance&gt;.ribbon.OkToRetryOnAllOperations=true
  &lt;instance&gt;.ribbon.MaxAutoRetriesNextServer=1
  &lt;instance&gt;.ribbon.MaxAutoRetries=0
  hystrix.command.&lt;instance&gt;.execution.isolation.strategy=THREAD
  hystrix.command.&lt;instance&gt;.execution.isolation.thread.timeoutInMilliseconds=360000
  hystrix.threadpool.&lt;instance&gt;.coreSize=40
  hystrix.command.&lt;instance&gt;.circuitBreaker.forceClosed=true
  hystrix.threadpool.&lt;instance&gt;.maximumSize=100
  hystrix.threadpool.&lt;instance&gt;.queueSizeRejectionThreshold=80
  </code></pre>
  
  <p>We were having the coreSize, forceClosed, maxQueueSize and quoteSizeRejectionThreshold as default and not it is configured this level.  It still has the issue.  We tried restart Gateway and Eureka instance.</p>