CloudWatch Exporter

An exporter for Amazon CloudWatch, for Prometheus.

Building and running

Cloudwatch Exporter requires at least Java 8.

mvn package to build.

java -jar target/cloudwatch_exporter-*-SNAPSHOT-jar-with-dependencies.jar 9106 example.yml to run.

The most recent pre-built JAR can be found at http://search.maven.org/#search%7Cga%7C1%7Ca%3A%22cloudwatch_exporter%22

Credentials and permissions

The CloudWatch Exporter uses the AWS Java SDK, which offers a variety of ways to provide credentials. This includes the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables.

The cloudwatch:ListMetrics and cloudwatch:GetMetricStatistics IAM permissions are required.

Configuration

The configuration is in YAML, an example with common options:

---
region: eu-west-1
metrics:
 - aws_namespace: AWS/ELB
   aws_metric_name: RequestCount
   aws_dimensions: [AvailabilityZone, LoadBalancerName]
   aws_dimension_select:
     LoadBalancerName: [myLB]
   aws_statistics: [Sum]

Name	Description
region	Required. The AWS region to connect to.
role_arn	Optional. The AWS role to assume. Useful for retrieving cross account metrics.
metrics	Required. A list of CloudWatch metrics to retrieve and export
aws_namespace	Required. Namespace of the CloudWatch metric.
aws_metric_name	Required. Metric name of the CloudWatch metric.
aws_dimensions	Optional. Which dimension to fan out over.
aws_dimension_select	Optional. Which dimension values to filter. Specify a map from the dimension name to a list of values to select from that dimension.
aws_dimension_select_regex	Optional. Which dimension values to filter on with a regular expression. Specify a map from the dimension name to a list of regexes that will be applied to select from that dimension.
aws_statistics	Optional. A list of statistics to retrieve, values can include Sum, SampleCount, Minimum, Maximum, Average. Defaults to all statistics unless extended statistics are requested.
aws_extended_statistics	Optional. A list of extended statistics to retrieve. Extended statistics currently include percentiles in the form pN or pN.N.
delay_seconds	Optional. The newest data to request. Used to avoid collecting data that has not fully converged. Defaults to 600s. Can be set globally and per metric.
range_seconds	Optional. How far back to request data for. Useful for cases such as Billing metrics that are only set every few hours. Defaults to 600s. Can be set globally and per metric.
period_seconds	Optional. Period to request the metric for. Only the most recent data point is used. Defaults to 60s. Can be set globally and per metric.
set_timestamp	Optional. Boolean for whether to set the Prometheus metric timestamp as the original Cloudwatch timestamp. For some metrics which are updated very infrequently (such as S3/BucketSize), Prometheus may refuse to scrape them if this is set to true (see #100). Defaults to true. Can be set globally and per metric.

The above config will export time series such as

# HELP aws_elb_request_count_sum CloudWatch metric AWS/ELB RequestCount Dimensions: ["AvailabilityZone","LoadBalancerName"] Statistic: Sum Unit: Count
# TYPE aws_elb_request_count_sum gauge
aws_elb_request_count_sum{job="aws_elb",load_balancer_name="mylb",availability_zone="eu-west-1c",} 42.0
aws_elb_request_count_sum{job="aws_elb",load_balancer_name="myotherlb",availability_zone="eu-west-1c",} 7.0

All metrics are exported as gauges.

In addition cloudwatch_exporter_scrape_error will be non-zero if an error occurred during the scrape, and cloudwatch_exporter_scrape_duration_seconds contains the duration of that scrape.

Timestamps

CloudWatch has been observed to sometimes take minutes for reported values to converge. The default delay_seconds will result in data that is at least 10 minutes old being requested to mitigate this. The samples exposed will have the timestamps of the data from CloudWatch, so usual staleness semantics will not apply and values will persist for 5m for instant vectors.

In practice this means that if you evaluate an instant vector at the current time, you will not see data from CloudWatch. An expression such as aws_elb_request_count_sum offset 10m will allow you to access the data, and should be used in recording rules and alerts.

For certain metrics which update relatively rarely, such as from S3, set_timestamp should be configured to false so that they are not exposed with a timestamp. This is as the true timestamp from CloudWatch could be so old that Prometheus would reject the sample.

Special handling for certain DynamoDB metrics

The DynamoDB metrics listed below break the usual CloudWatch data model.

• ConsumedReadCapacityUnits
• ConsumedWriteCapacityUnits
• ProvisionedReadCapacityUnits
• ProvisionedWriteCapacityUnits
• ReadThrottleEvents
• WriteThrottleEvents

When these metrics are requested in the TableName dimension CloudWatch will return data only for the table itself, not for its Global Secondary Indexes. Retrieving data for indexes requires requesting data across both the TableName and GlobalSecondaryIndexName dimensions. This behaviour is different to that of every other CloudWatch namespace and requires that the exporter handle these metrics differently to avoid generating duplicate HELP and TYPE lines.

When exporting one of the problematic metrics for an index the exporter will use a metric name in the format aws_dynamodb_METRIC_index_STATISTIC rather than the usual aws_dynamodb_METRIC_STATISTIC. The regular naming scheme will still be used when exporting these metrics for a table, and when exporting any other DynamoDB metrics not listed above.

Reloading Configuration

There are two ways to reload configuration:

1. Send a SIGHUP signal to the pid: kill -HUP 1234
2. POST to the reload endpoint: curl -X POST localhost:9106/-/reload

If an error occurs during the reload, check the exporter's log output.

Cost

Amazon charges for every API request, see the current charges.

Every metric retrieved requires one API request, which can include multiple statistics. In addition, when aws_dimensions is provided, the exporter needs to do API requests to determine what metrics to request. This should be negligible compared to the requests for the metrics themselves.

In the case that all aws_dimensions are provided in the aws_dimension_select list, the exporter will not perform the above API request. It will request all possible combination of values for those dimensions. This will reduce cost as the values for the dimensions do not need to be queried anymore, assuming that all possible value combinations are present in CloudWatch.

If you have 100 API requests every minute, with the price of USD$10 per million requests (as of Aug 2018), that is around $45 per month. The cloudwatch_requests_total counter tracks how many requests are being made.

Docker Image

To run the CloudWatch exporter on Docker, you can use the prom/cloudwatch-exporter image. It exposes port 9106 and expects the config in /config/config.yml. To configure it, you can bind-mount a config from your host:

$ docker run -p 9106 -v /path/on/host/config.yml:/config/config.yml prom/cloudwatch-exporter

Specify the config as the CMD:

$ docker run -p 9106 -v /path/on/host/us-west-1.yml:/config/us-west-1.yml prom/cloudwatch-exporter /config/us-west-1.yml

Or create a config file named /config/config.yml along with following Dockerfile in the same directory and build it with docker build:

FROM prom/cloudwatch-exporter