AWS Systems Manager
User Guide

Reference: ec2messages, ssmmessages, and Other API Calls

If you monitor API calls, you might see calls to the following APIs.

  • ec2messages:AcknowledgeMessage

  • ec2messages:DeleteMessage

  • ec2messages:FailMessage

  • ec2messages:GetEndpoint

  • ec2messages:GetMessages

  • ec2messages:SendReply

  • ssmmessages:CreateControlChannel

  • ssmmessages:CreateDataChannel

  • ssmmessages:OpenControlChannel

  • ssmmessages:OpenDataChannel

  • UpdateInstanceInformation

  • ListInstanceAssociations

  • DescribeInstanceProperties

  • DescribeDocumentParameters

These special calls are used by Systems Manager for various operations.

ec2messages API calls

Calls to ec2messages:* APIs are calls to the ec2messages endpoint. Systems Manager uses this endpoint to make calls from SSM Agent to the Systems Manager service in the cloud. This endpoint is required to send and receive commands.

ssmmessages API calls

Systems Manager uses the ssmmessages endpoint to to make calls from SSM Agent to the Session Manager service in the cloud. This endpoint is required to create and delete session channels with the Session Manager service in the cloud.

Instance-related API calls

UpdateInstanceInformation: SSM Agent calls the Systems Manager service in the cloud every five minutes to provide heartbeat information. This call is necessary to maintain a heartbeat with the agent so that the service knows the agent is functioning as expected.

ListInstanceAssociations: The agent calls this API to see if a new Systems Manager State Manager association is available. This API is required for State Manager to function.

DescribeInstanceProperties and DescribeDocumentParameters: Systems Manager calls these APIs to render specific nodes in the Amazon EC2 console. The DescribeInstanceProperties API displays the Managed Instances node in the left navigation. The DescribeDocumentParameters API displays the Documents node in the left navigation.