UnHealthyHostCount, Latency

Number of healthy EC2 instances registered with the load balancer in the specified Availability Zone. Hosts that do not fail the health check beyond the unhealthy threshold are considered healthy. When evaluating this metric, the dimensions should be defined by LoadBalancerName and AvailabilityZone.
This metric represents the number of healthy instances in the specified Availability Zone. Instances may become unhealthy due to connection problems such as non-200 responses (for HTTP and HTTPS health checks) and timeouts when doing health checks. In order to get the total number of all healthy hosts, this metric needs to get each registered AvailabilityZone and add all metrics together.

The elapsed time from request leaving the load balancer to receiving the corresponding response.

CloudWatch Logs

CloudWatch Logs is a log monitoring service provided by AWS. Collect OS logs and application logs of EC2 instances and monitor them in real time.

Amazon CloudWatch is an application monitoring service that runs on AWS. Can use Amazon CloudWatch to gain visibility into resource utilization, application performance, and operation status across the system. Use these insights to respond and keep your application running smoothly.

With CloudWatch Logs, can mainly used for:
– Log accumulation (you can set the retention period)
– Specific character filtering
– Graph what matched the filter pattern
– Alert settings linked with Amazon SNS(Simple Notification Service)










CloudWatch is a monitoring service for AWS resources and applications running on AWS. You can collect and monitor metrics and log files of various AWS services and set alarms. When you start the corresponding AWS service, data points are regularly sent to CloudWatch, so you can view and analyze the metrics on a graphical screen without being particularly aware. With custom metrics, you can use graphical graphs for metrics collected from your own application. Using the alarm function, not only notification using SNS, addition of EC2 instance by Auto Scaling, or recovery of EC2 instance is also possible.

Data points, metrics
When you start a supported AWS service, data points (monitoring data) are sent to CloudWatch stores data points in metrics.
Metrics can be thought of as monitored variables, and data points can be thought of as the values of variables over time. Data points are not necessarily related to AWS services. It may be the data sent by the script created by the user. In other words, the metric may be the CPU utilization of an EC2 instance, or it may be the response speed of the application or room temperature.
Metrics are identified by name, namespace, and one or more dimensions. Metrics are stored for two weeks.

Name space
Namespaces store metrics. The metric name [CPUUtilization] is used in EC2 and RDS. The namespace [AWS/EC2] or [AWS/RDS] is used as one element to identify metrics.

Dimensions are categories of metrics. Statistical monitoring is possible using dimensions. Use the dimension [InstanceId] to check the metrics of an instance. You can use the dimension [AutoScalingGroupName] to monitor data for each autoscaling group.

EC2 Metrics Dimension



AWS CloudWatch

Amazon CloudWatch provides real-time monitoring of Amazon Web Service (AWS) resources and the applications that user are running on AWS. You can use CloudWatch to collect and track metrics. Metrics are variables that can be measured in terms of resources and applications.

The CloudWatch homepage automatically displays metrics about each of the AWS services you are using. In addition, you can create custom dashboards to view custom application metrics or view custom collections of selected metrics.

You can monitor metrics and create alarms that send notifications when thresholds are exceeded or automatically change the resources being monitored. For example, you can monitor CPU usage and disk reads and writes for Amazon EC2 instances, and use that data to decide whether you should launch additional instances to handle the increased load. You can also use this data to save money by shutting down underutilized instances.

What can we do aws monitoring tool “cloud watch”?

What can we do for CloudWatch??

-> CloudWatch is “A fully managed operation monitoring service” provided by AWS, those that monitor various resources of AWS.

In detail and features.
– Can be used without setup
– It detects an abnormal condition and automatically restores it
– Alert notification and action can be set according to metrics.

It can be monitored EC2, EBS, S3, and so on. Cloudwatch have three services.
– CloudWatch : You can make dashboards by graphing multiple items such as CPU and memory.
– CloudWatch Logs:Corresponds to Amazon Linux, RedHat, Windows etc, and by acquiring various logs by putting an agent in the instance. In addtion to OS, application logs are also supported, and you can let alert notice by keyword.
– CloudWatch Events:It is a service that causes some action to be executed by triggering API event.

Other way to watch log is checking access_log, error_log, and monitor_log from Linux.