Amazon CloudWatch
User Guide

Publishing Custom Metrics

You can publish your own metrics to CloudWatch using the AWS CLI or an API. You can view statistical graphs of your published metrics with the AWS Management Console.

CloudWatch stores data about a metric as a series of data points. Each data point has an associated time stamp. You can even publish an aggregated set of data points called a statistic set.

High-Resolution Metrics

Each metric is one of the following:

  • Standard resolution, with data having a one-minute granularity

  • High resolution, with data at a granularity of one second

Metrics produced by AWS services are standard resolution by default. When you publish a custom metric, you can define it as either standard resolution or high resolution. When you publish a high-resolution metric, CloudWatch stores it with a resolution of 1 second, and you can read and retrieve it with a period of 1 second, 5 seconds, 10 seconds, 30 seconds, or any multiple of 60 seconds.

High-resolution metrics can give you more immediate insight into your application's sub-minute activity. Keep in mind that every PutMetricData call for a custom metric is charged, so calling PutMetricData more often on a high-resolution metric can lead to higher charges. For more information about CloudWatch pricing, see Amazon CloudWatch Pricing.

If you set an alarm on a high-resolution metric, you can specify a high-resolution alarm with a period of 10 seconds or 30 seconds, or you can set a regular alarm with a period of any multiple of 60 seconds. There is a higher charge for high-resolution alarms with a period of 10 or 30 seconds.

Using Dimensions

In custom metrics, the --dimensions parameter is common. A dimension further clarifies what the metric is and what data it stores. You can have up to 10 dimensions in one metric, and each dimension is defined by a name and value pair.

How you specify a dimension is different when you use different commands. With put-metric-data, you specify each dimension as MyName=MyValue, and with get-metric-statistics or put-metric-alarm you use the format Name=MyName, Value=MyValue. For example, the following command publishes a Buffers metric with two dimensions named InstanceId and InstanceType.

aws cloudwatch put-metric-data --metric-name Buffers --namespace MyNameSpace --unit Bytes --value 231434333 --dimensions InstanceId=1-23456789,InstanceType=m1.small

This command retrieves statistics for that same metric. Separate the Name and Value parts of a single dimension with commas, but if you have multiple dimensions, use a space between one dimension and the next.

aws cloudwatch get-metric-statistics --metric-name Buffers --namespace MyNameSpace --dimensions Name=InstanceId,Value=1-23456789 Name=InstanceType,Value=m1.small --start-time 2016-10-15T04:00:00Z --end-time 2016-10-19T07:00:00Z --statistics Average --period 60

If a single metric includes multiple dimensions, you must specify a value for every defined dimension when you use get-metric-statistics. For example, the Amazon S3 metric BucketSizeBytes includes the dimensions BucketName and StorageType, so you must specify both dimensions with get-metric-statistics.

aws cloudwatch get-metric-statistics --metric-name BucketSizeBytes --start-time 2017-01-23T14:23:00Z --end-time 2017-01-26T19:30:00Z --period 3600 --namespace AWS/S3 --statistics Maximum --dimensions Name=BucketName,Value=MyBucketName Name=StorageType,Value=StandardStorage --output table

To see what dimensions are defined for a metric, use the list-metrics command.

Publishing Single Data Points

To publish a single data point for a new or existing metric, use the put-metric-data command with one value and time stamp. For example, the following actions each publish one data point.

aws cloudwatch put-metric-data --metric-name PageViewCount --namespace MyService --value 2 --timestamp 2016-10-20T12:00:00.000Z aws cloudwatch put-metric-data --metric-name PageViewCount --namespace MyService --value 4 --timestamp 2016-10-20T12:00:01.000Z aws cloudwatch put-metric-data --metric-name PageViewCount --namespace MyService --value 5 --timestamp 2016-10-20T12:00:02.000Z

If you call this command with a new metric name, CloudWatch creates a metric for you. Otherwise, CloudWatch associates your data with the existing metric that you specified.

Note

When you create a metric, it can take up to 2 minutes before you can retrieve statistics for the new metric using the get-metric-statistics command. However, it can take up to 15 minutes before the new metric appears in the list of metrics retrieved using the list-metrics command.

Although you can publish data points with time stamps as granular as one-thousandth of a second, CloudWatch aggregates the data to a minimum granularity of 1 second. CloudWatch records the average (sum of all items divided by number of items) of the values received for each period, as well as the number of samples, maximum value, and minimum value for the same time period. For example, the PageViewCount metric from the previous examples contains three data points with time stamps just seconds apart. If you have your period set to 1 minute, CloudWatch aggregates the three data points because they all have time stamps within a 1-minute period.

You can use the get-metric-statistics command to retrieve statistics based on the data points that you published.

aws cloudwatch get-metric-statistics --namespace MyService --metric-name PageViewCount \ --statistics "Sum" "Maximum" "Minimum" "Average" "SampleCount" \ --start-time 2016-10-20T12:00:00.000Z --end-time 2016-10-20T12:05:00.000Z --period 60

The following is example output.

{ "Datapoints": [ { "SampleCount": 3.0, "Timestamp": "2016-10-20T12:00:00Z", "Average": 3.6666666666666665, "Maximum": 5.0, "Minimum": 2.0, "Sum": 11.0, "Unit": "None" } ], "Label": "PageViewCount" }

Publishing Statistic Sets

You can aggregate your data before you publish to CloudWatch. When you have multiple data points per minute, aggregating data minimizes the number of calls to put-metric-data. For example, instead of calling put-metric-data multiple times for three data points that are within 3 seconds of each other, you can aggregate the data into a statistic set that you publish with one call, using the --statistic-values parameter.

aws cloudwatch put-metric-data --metric-name PageViewCount --namespace MyService --statistic-values Sum=11,Minimum=2,Maximum=5,SampleCount=3 --timestamp 2016-10-14T12:00:00.000Z

CloudWatch needs raw data points to calculate percentiles. If you publish data using a statistic set instead, you can't retrieve percentile statistics for this data unless one of the following conditions is true:

  • The SampleCount of the statistic set is 1

  • The Minimum and the Maximum of the statistic set are equal

Publishing the Value Zero

When your data is more sporadic and you have periods that have no associated data, you can choose to publish the value zero (0) for that period or no value at all. If you use periodic calls to PutMetricData to monitor the health of your application, you might want to publish zero instead of no value. For example, you can set a CloudWatch alarm to notify you if your application fails to publish metrics every five minutes. You want such an application to publish zeros for periods with no associated data.

You might also publish zeros if you want to track the total number of data points or if you want statistics such as minimum and average to include data points with the value 0.