Reboot an instance, with a Cloud Watch Alarms based on custom metric

Question

My EC2 instance periodically send a custom metric with :

```
aws cloudwatch put-metric-data  --namespace "CICD" --dimensions InstanceID="$MY_INSTANCEID" --metric-name "CICD_IS_UP" --unit Count --value "$is_up" --region eu-west-1
```

So the metric, in the namespace "CICD" contains the InstanceID and a CICD_IS_UP value (0 when down, 1 when up).  
  
I want to have an automatic action to reboot the instance when the metric is 0 (CICD down !).  
  
So, I created a CloudWatch ALARM :  
- I select the metric in CICD namespace  
- I define metric level etc...  
- Because the metric is defined with an InstanceID dimension, I can see the value of the Id in the "InstanceID" field of the metric wizzard  
- But on the "Configure Actions" step, the "EC2 Action" panel contains "This action is only available for EC2 Per-Instance Metrics" but it is greyed : I'm unable to add an EC2 action.  
  
How can I enable EC2 action on a custom metric ? The metric have the InstanceID dimension, but CloudWatch Alarms seems to ignore it.  
  
Edited by: JeromeF on Nov 29, 2019 4:58 AM  
  
Edited by: JeromeF on Nov 29, 2019 4:59 AM

Answer

After double-double-checking on other AWS account, I found the problem : the dimension name for the instance must be spelled **InstanceId**, not **InstanceID**.  
  
Strange behavior of the Create Alarm wizzard : it detects the instance ID even if it is spelled ID instead of Id. But the Action will not be enabled.

Reboot an instance, with a Cloud Watch Alarms based on custom metric

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