title: Scaling out GAE when memory utilization exceeds limit
body: <p>I am using GAE for heavy tasks with high memory needs. And I got the following error:</p>
  
  <pre><code>Exceeded soft memory limit of 512 MB with 561 MB 
  after servicing 3 requests total. 
  Consider setting a larger instance class in app.yaml.
  </code></pre>
  
  <p>As the tasks are expensive, I assume that two applications can work within one instance. But it does not work for three applications:</p>
  
  <pre><code>While handling this request, 
  the process that handled this request was found to be using 
  too much memory and was terminated. 
  This is likely to cause a new process to be used 
  for the next request to your application. 
  If you see this message frequently, 
  you may have a memory leak in your application or may be 
  using an instance with insufficient memory.
  Consider setting a larger instance class in app.yaml.
  </code></pre>
  
  <p>My current settings: </p>
  
  <pre><code>runtime: nodejs8
  instance_class: B4
  basic_scaling:
  max_instances: 10
  idle_timeout: 1m
  </code></pre>
  
  <p>I also tried with these settings:</p>
  
  <pre><code>runtime: nodejs8
  instance_class: F4
  automatic_scaling:
    target_cpu_utilization: 0.5
    max_instances: 10
  </code></pre>
  
  <p>The failure of executing the task is "<strong>Exceeded soft memory limit</strong>".
  So, to solve this error, I think the scale out should be done based on the "memory utilization" rather than "cpu utilization".</p>
  
  <p>How can scaling out be done when the memory utilization exceeds the limit?</p>