Amazon ECS service utilization metrics

The service utilization metrics are available for CPU, memory, and, when there is an EBS volume attached to your tasks, EBS filesystem utilization. The service level metrics are supported for services with tasks hosted on both Amazon EC2 instances and Fargate.

Service level CPU and memory utilization

The CPU and memory utilization is measured as the percentage of CPU and memory that is used by the Amazon ECS tasks that belong to a service on a cluster when compared to the CPU and memory that is specified in the service's task definition.

                                      (Total CPU units used by tasks in service) x 100
Service CPU utilization =  ----------------------------------------------------------------------------
                           (Total CPU units specified in task definition) x (number of tasks in service)

                                       (Total MiB of memory used by tasks in service) x 100
Service memory utilization =  --------------------------------------------------------------------------------
                              (Total MiB of memory specified in task definition) x (number of tasks in service)

Each minute, the Amazon ECS container agent calculates the number of CPU units and MiB of memory that are currently being used for each task owned by the service, and this information is reported back to Amazon ECS. The total amount of CPU and memory used for all tasks owned by the service that are running on the cluster is calculated, and those numbers are reported to CloudWatch as a percentage of the total resources that are specified for the service in the service's task definition. If you specify a soft limit (memoryReservation), it's used to calculate the amount of reserved memory. Otherwise, the hard limit (memory) is used. For more information about hard and soft limits, see Task size.

For example, the task definition for a service specifies a total of 512 CPU units and 1,024 MiB of memory (with the hard limit memory parameter) for all of its containers. The service has a desired count of 1 running task, the service is running on a cluster with 1 c4.large container instance (with 2,048 CPU units and 3,768 MiB of total memory), and there are no other tasks running on the cluster. Although the task specifies 512 CPU units, because it is the only running task on a container instance with 2,048 CPU units, it can use up to four times the specified amount (2,048 / 512). However, the specified memory of 1,024 MiB is a hard limit and it can't be exceeded, so in this case, service memory utilization can't exceed 100%.

If the previous example used the soft limit memoryReservation instead of the hard limit memory parameter, the service's tasks could use more than the specified 1,024 MiB of memory as needed. In this case, the service's memory utilization could exceed 100%.

If your application has a sudden spike in memory utilization for a short amount of time, you will not see the service memory utilization increasing because Amazon ECS collects multiple data points every minute, and then aggregates them to one data point that is sent to CloudWatch.

If this task is performing CPU-intensive work during a period and using all 2,048 of the available CPU units and 512 MiB of memory, the service reports 400% CPU utilization and 50% memory utilization. If the task is idle and using 128 CPU units and 128 MiB of memory, the service reports 25% CPU utilization and 12.5% memory utilization.

Service level EBS filesystem utilization

The service level EBS filesystem utilization is measured as the total amount of the EBS filesystem in use by the tasks that belong to the service, divided by the total amount of EBS filesystem storage that is allocated for all tasks that belong to the service.

                                       (Total GB of EBS filesystem used by tasks in the service x 100)
Service EBS filesystem utilization =  -----------------------------------------------------------------
                                       (Total GB of EBS filesystem allocated to tasks in the service)

Service RUNNING task count

You can use CloudWatch metrics to view the number of tasks in your services that are in the RUNNING state. For example, you can set a CloudWatch alarm for this metric to alert you if the number of running tasks in your service falls below a specified value.

Service RUNNING task count in Amazon ECS CloudWatch Container Insights

A "Number of Running Tasks" (RunningTaskCount) metric is available per cluster and per service when you use Amazon ECS CloudWatch Container Insights. You can use Container Insights for all new clusters created by opting in to the containerInsights account setting, on individual clusters by turning on the cluster settings during cluster creation, or on existing clusters by using the UpdateClusterSettings API. Metrics collected by CloudWatch Container Insights are charged as custom metrics. For more information about CloudWatch pricing, see CloudWatch Pricing.

To view this metric, see Amazon ECS Container Insights Metrics in the Amazon CloudWatch User Guide.