title: Hystrix command fails with "timed-out and no fallback available"
body: <p>I've noticed that some of the commands in my application fail with </p>
  
  <pre><code>Caused by: ! com.netflix.hystrix.exception.HystrixRuntimeException: GetAPICommand timed-out and no fallback available.
  out: ! at com.netflix.hystrix.HystrixCommand.getFallbackOrThrowException(HystrixCommand.java:1631)
  out: ! at com.netflix.hystrix.HystrixCommand.access$2000(HystrixCommand.java:97)
  out: ! at com.netflix.hystrix.HystrixCommand$TimeoutObservable$1$1.tick(HystrixCommand.java:1025)
  out: ! at com.netflix.hystrix.HystrixCommand$1.performBlockingGetWithTimeout(HystrixCommand.java:621)
  out: ! at com.netflix.hystrix.HystrixCommand$1.get(HystrixCommand.java:516)
  out: ! at com.netflix.hystrix.HystrixCommand.execute(HystrixCommand.java:425)
  out: Caused by: ! java.util.concurrent.TimeoutException: null
  out: !... 11 common frames omitted
  </code></pre>
  
  <p>This is my Hystrix configuration override:</p>
  
  <pre><code>hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=210000
  hystrix.threadpool.default.coreSize=50
  hystrix.threadpool.default.maxQueueSize=100
  hystrix.threadpool.default.queueSizeRejectionThreshold=50
  </code></pre>
  
  <p>What kind of timeout is this? Is it a read/connection timeout to the external application? How do I go about debugging this?</p>