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An easy interface to query the EC2 metadata API, with caching.

Project description

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An easy interface to query the EC2 metadata API (version 2), with caching.

A quick example:

>>> from ec2_metadata import ec2_metadata
>>> print(ec2_metadata.region)
us-east-1
>>> print(ec2_metadata.instance_id)
i-123456

Installation

Use pip:

python -m pip install ec2-metadata

Python 3.7 to 3.11 supported.


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Why?

boto came with a utility function to retrieve the instance metadata as a lazy loading dictionary, boto.utils.get_instance_metadata, but this has not been ported to boto3, as per this issue. I thought that rather than building a new version inside boto3 it would work well as a standalone library.

Instance Metadata Service Version 2

In November 2019, AWS released version 2 of the instance metadata service. It’s more secure against Server Side Request Forgery (SSRF) attacks.

ec2-metadata now uses it exclusively. You can therefore consider disabling version 1, as per AWS’ guide.

API

EC2Metadata(session=None)

A container that represents the data available on the EC2 metadata service. Attributes don’t entirely correspond to the paths in the metadata service - they have been ‘cleaned up’. You may also want to refer to the metadata service docs to understand the exact contents.

There’s a singleton instance of it at the name ec2_metadata which should cover 90% of use cases. Use it like:

from ec2_metadata import ec2_metadata

ec2_metadata.region

The session argument, if provided, should be an instance of requests.Session, allowing you to customize the way requests are made.

Most of the attributes are cached, except where noted below. This is because they are mostly immutable, or at least require an instance stop to change. However some cached attributes do represent things that can change without an instance stop, but rarely do, such as network devices.

The caching is done with @cached_property, so they cache on first access. If you want to clear the cache of one attribute you can just del it:

del ec2_metadata.network_interfaces

To clear all, use the clear_all() method as per below.

account_id: str

The current AWS account ID, e.g. '123456789012'.

ami_id: str

The ID of the AMI used to launch the instance, e.g. 'ami-123456'.

autoscaling_target_lifecycle_state: str | None

Uncached. The target Auto Scaling lifecycle state that the instance is transitionioning to, or None if the instance is not in an autoscaling group. See AWS docs page Retrieve the target lifecycle state through instance metadata.

availability_zone: str

The name of the current AZ e.g. 'eu-west-1a'.

availability_zone_id: str | None

The unique, cross-account ID of the current AZ e.g. 'use1-az6'. See AWS docs page AZ IDs for your AWS resources.

ami_launch_index: int

The index of the instance in the launch request, zero-based, e.g. 0.

ami_manifest_path: str

The path to the AMI manifest file in Amazon S3, or '(unknown)' on EBS-backed AMI’s.

clear_all() -> None

Clear all the cached attributes on the class, meaning their next access will re-fetch the data from the metadata API. This includes clearing the token used to authenticate with the service.

domain: str

The domain for AWS resources for the region. E.g. 'amazonaws.com' for the standard AWS regions and GovCloud (US), or 'amazonaws.com.cn' for China.

iam_info: dict | None

A dictionary of data for the IAM role attached to the instance, or None if no role is attached.

iam_security_credentials: dict | None

A dictionary of data for the security credentials associated with the IAM role attached to the instance, or None if no role is attached.

See the AWS docs section “Retrieve security credentials from instance metadata“ for more details.

instance_action: str

Uncached. A state that notifies if the instance will reboot in preparation for bundling. See the AWS docs section “Instance Metadata Categories” for the valid values.

instance_id: str

The current instance’s ID, e.g. 'i-123456'

instance_identity_document: dict

A dictionary of dynamic data - see AWS docs page “Instance Identity Documents”.

instance_profile_arn: str | None

The ARN of the IAM role/instance profile attached to the instance, taken from iam_info, or None if no role is attached.

instance_profile_id: str | None

The ID of the IAM role/instance profile attached to the instance, taken from iam_info, or None if no role is attached.

instance_profile_name: str | None

The instance profile name, extracted from instance_profile_arn, or None if no role is attached.

instance_type: str

The current instance’s type, e.g. 't2.nano'

kernel_id: str | None

The current instance’s kernel ID, or None if it doesn’t have one, e.g. 'aki-dc9ed9af'.

mac : str

The instance’s MAC address, e.g. '0a:d2:ae:4d:f3:12'

network_interfaces: dict[str, NetworkInterface]

A dictionary of mac address to NetworkInterface, which represents the data available on a network interface - see below. E.g. {'01:23:45:67:89:ab': NetworkInterface('01:23:45:67:89:ab')}

partition: str

The AWS partition where the instance is running. E.g. 'aws' for the standard AWS regions, 'aws-us-gov' for GovCloud (US), or 'aws-cn' for China.

private_hostname : str

The private IPv4 DNS hostname of the instance, e.g. 'ip-172-30-0-0.eu-west-1.compute.internal' .

private_ipv4: str

The private IPv4 of the instance, e.g. '172.30.0.0'.

public_hostname : str | None

The public DNS hostname of the instance, or None if the instance is not public, e.g. 'ec2-1-2-3-4.compute-1.amazonaws.com'.

public_ipv4: str | None

The public IPv4 address of the instance, or None if the instance is not public, e.g. '1.2.3.4'.

region: str

The region the instance is running in, e.g. 'eu-west-1'.

reservation_id: str

The ID of the reservation used to launch the instance, e.g. 'r-12345678901234567'.

security_groups : list[str]

List of security groups by name, e.g. ['ssh-access', 'custom-sg-1'].

spot_instance_action: SpotInstanceAction | None

Uncached. An object describing an action about to happen to this spot instance. Returns None if the instance is not spot, or not marked for termination.

The SpotInstanceAction object has two attributes:

  • action: str - the action about to happen, one of "hibernate", "stop", or "terminate".
  • time: datetime - the approximate UTC datetime when the action will occur.

See AWS docs section for a little more information.

tags: InstanceTags

A dict-like mapping of the tags for the instance (documented below). This requires you to explicitly enable the feature for the instance. If the feature is not enabled, accessing this attribute raises an error.

(It also seems that there is a bug where if the feature is enabled and then disabled, the metadata service returns an empty response. This is indistinguishable from “no tags”, so beware that in that case, InstanceTags will just look like an empty mapping.)

user_data: bytes | None

The raw user data assigned to the instance (not base64 encoded), or None if there is none.

InstanceTags

A dict-like mapping of tag names to values (both strs). To avoid unnecessary requests, the mapping is lazy: values are only fetched when required. (Names are known on construction though, from the first request in EC2Metadata.tags.)

The metadata service will receive tag updates on some instance types, as per the AWS documentation:

If you add or remove an instance tag, the instance metadata is updated while the instance is running for instances built on the Nitro System, without needing to stop and then start the instance. For all other instances, to update the tags in the instance metadata, you must stop and then start the instance.

Because InstanceTags is cached, it won’t reflect such updates on Nitro instances unless you clear it first:

del ec2_metadata.tags
ec2_metadata.tags["Name"]  # fresh

NetworkInterface

Represents a single network interface, as retrieved from EC2Metadata.network_interfaces. Again like EC2Metadata all its attributes cache on first access, and can be cleared with del or its clear_all() method.

device_number: int

The unique device number associated with that interface, e.g. 0.

interface_id: str

The unique id used to identify the Elastic Network Interface, e.g. 'eni-12345'.

ipv4_associations: dict[str, list[str]]

A dictionary mapping public IP addresses on the interface to the list of private IP addresses associated with that public IP, for each public IP that is associated with the interface, e.g. {'54.0.0.1': ['172.30.0.0']}.

ipv6s: list[str]

The IPv6 addresses associated with the interface, e.g. ['2001:db8:abcd:ef00::1234'].

mac: str

The MAC address of the interface, e.g. '01:23:45:67:89:ab'.

owner_id: str

The AWS Account ID of the owner of the network interface, e.g. '123456789012'.

private_hostname: str

The interface’s local/private hostname, e.g. 'ip-172-30-0-0.eu-west-1.compute.internal'.

private_ipv4s: list[str]

The private IPv4 addresses associated with the interface, e.g. ['172.30.0.0'].

public_hostname: str | None

The interface’s public DNS (IPv4), e.g. 'ec2-54-0-0-0.compute-1.amazonaws.com'.

public_ipv4s: list[str]

The Elastic IP addresses associated with the interface, e.g. ['54.0.0.0'].

security_groups: list[str]

The names of the security groups to which the network interface belongs, e.g. ['ssh-access', 'custom-sg-1'].

security_group_ids: list[str]

The names of the security groups to which the network interface belongs, e.g. ['sg-12345678', 'sg-12345679'].

subnet_id: str

The ID of the subnet in which the interface resides, e.g. 'subnet-12345678'.

subnet_ipv4_cidr_block: str | None

The IPv4 CIDR block of the subnet in which the interface resides, or None if there is none, e.g. '172.30.0.0/24'.

subnet_ipv6_cidr_blocks: list[str]

The list of IPv6 CIDR blocks of the subnet in which the interface resides, e.g. ['2001:db8:abcd:ef00::/64']. If the subnet does not have any IPv6 CIDR blocks or the instance isn’t in a VPC, the list will be empty, e.g. [].

vpc_id: str

The ID of the VPC in which the interface resides, e.g. 'vpc-12345678'.

vpc_ipv4_cidr_block: str | None

The IPv4 CIDR block of the VPC, or None if the instance isn’t in a VPC, e.g. '172.30.0.0/16'.

vpc_ipv4_cidr_blocks: list[str]

The list of IPv4 CIDR blocks e.g. ['172.30.0.0/16']. If the interface doesn’t have any such CIDR blocks, the list will be empty.

vpc_ipv6_cidr_blocks: list[str]

The list of IPv6 CIDR blocks of the VPC in which the interface resides, e.g. ['2001:db8:abcd:ef00::/56']. If the VPC does not have any IPv6 CIDR blocks or the instance isn’t in a VPC, the list will be empty, e.g. [].

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