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rugbert
Asked: 2020-04-05 08:33:40 +0800 CST

AWS Beanstalk Auto-scaling Scaling Triggers with UnhealthyHost count and Health Checking

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I have my scaling triggers set to look for an un-healthy host count but it does not seem to be working. my configuration settings

Now to test this - I am SSHing into one of my instances and halting the HTTPD service. Then, when I navigate to the health overview, I will immediately see that the server I SSHd into now has the status of severe.

severe === unhealthy?

I would assume that at this point, after 1 minute has passed (as per my rules) a new server would be created, but that is not happening.

If I am understanding my rules correctly - there is now 1 (the above the upper threshold) unhealthy server, so we increment up 1. And then once the number of unhealthy servers is 0 (below the lower threshold) then remove 1 sever.

But yeah, I waited around 5 minutes and no new EC2 servers were provisioned.

I also have some settings for the health check:

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Is this conflicting with my autoscaling rules somehow? I thought that the healthcheck file needs to return a 200 response to be considered healthy and if HTTPD is halted - they it would not return that response.

So what gives?

amazon-web-services elastic-beanstalk autoscaling

1 Answers

  1. It looks like you left the units set, which I don't think exist on that metric. You can go to the cloudwatch console and check the alarm and metric to see if they match.

    But Also, scaling on UnHealthyHostCount is a bad idea. Its just going to launch a new instance but not do anything about the unhealthy one. Instead enabling ELB Healthchecks is usually a better idea.

    https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/environmentconfig-autoscaling-healthchecktype.html

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