aws-instance-metadata-exporter

Spot instance termination exporter

Prometheus exporters are used to export metrics from third-party systems as Prometheus metrics - this is an exporter to scrape for AWS spot price termination notice on the instance for Hollowtrees.

Spot instance lifecycle

• User submits a bid to run a desired number of EC2 instances of a particular type. The bid includes the price that the user is willing to pay to use the instance for an hour.
• If the bid price exceeds the current spot price (that is determined by AWS based on current supply and demand) the instances are started.
• If the current spot price rises above the bid price or there is no available capacity, the spot instance is interrupted and reclaimed by AWS. 2 minutes before the interruption the internal metadata endpoint on the instance is updated with the termination info.
• If the instance is interrupted the action taken by AWS varies depending on the interruption behaviour (start, stop or hibernate) and the request type (one-time or persistent). These can be configured when requesting the instance. See more about this here

Spot instance termination notice

The Termination Notice is accessible to code running on the instance via the instance’s metadata at http://169.254.169.254/latest/meta-data/spot/termination-time. This field becomes available when the instance has been marked for termination and will contain the time when a shutdown signal will be sent to the instance’s operating system. At that time, the Spot Instance Request’s bid status will be set to marked-for-termination.
The bid status is accessible via the DescribeSpotInstanceRequests API for use by programs that manage Spot bids and instances.

Quick start

The project uses the promu Prometheus utility tool. To build the exporter promu needs to be installed. To install promu and build the exporter:

go get github.com/prometheus/promu
promu build

The following options can be configured when starting the exporter:

./spot-termination-exporter --help
Usage of ./spot-termintation-exporter:
  -bind-addr string
        bind address for the metrics server (default ":9189")
  -log-level string
        log level (default "info")
  -metadata-endpoint string
        metadata endpoint to query (default "http://169.254.169.254/latest/meta-data/")
  -metrics-path string
        path to metrics endpoint (default "/metrics")

Test locally

The AWS instance metadata is available at http://169.254.169.254/latest/meta-data/. By default this is the endpoint that is being queried by the exporter but it is quite hard to reproduce a termination notice on an AWS instance for testing, so the meta-data endpoint can be changed in the configuration. There is a test server in the utils directory that can be used to mock the behavior of the metadata endpoint. It listens on port 9092 and provides dummy responses for /instance-id and /spot/instance-action. It can be started with:

go run util/test_server.go

The exporter can be started with this configuration to query this endpoint locally:

./spot-termination-exporter --metadata-endpoint http://localhost:9092/latest/meta-data/ --log-level debug

Metrics

# HELP aws_instance_metadata_service_available Metadata service available
# TYPE aws_instance_metadata_service_available gauge
aws_instance_metadata_service_available{instance_id="i-0d2aab13057917887"} 1
# HELP aws_instance_termination_imminent Instance is about to be terminated
# TYPE aws_instance_termination_imminent gauge
aws_instance_termination_imminent{instance_action="stop",instance_id="i-0d2aab13057917887"} 1
# HELP aws_instance_termination_in Instance will be terminated in
# TYPE aws_instance_termination_in gauge
aws_instance_termination_in{instance_id="i-0d2aab13057917887"} 119.888545

Default Hollowtrees node exporters associated to alerts:

• AWS spot instance termination collector
• AWS autoscaling group exporter