protected void setFailure(Throwable ex, int RPid) {
    synchronized (this) {
      failure = ex;
      this.RPid = RPid;
      notify();
    }
  }
Returns the reply processor id for the current failed message. Returns 0 if it does not have
one. Note this method should only be called after getMessage has thrown an exception.
geode-core/src/main/java/org/apache/geode/internal/tcp/MsgDestreamer.java