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Description:

botoendpointurlshim 0.0.5

Boto Endpoint URL shim
Configure boto3 and botocore endpoint URL via environment variables or
shared configuration file.
This project is motivated by the yet-to-be-merged boto3 PR#2746, and
follows the aws-sdk proposal #230 (updated for commit b912470).
Quick start
To use the main interface described in proposal #230, set up either
service-specific environment variables or endpoint_url in a service-specific
sub-section of the shared configuration file and set up the proposed endpoint
URL resolution.
import boto_endpoint_url_shim
import boto3

boto_endpoint_url_shim.proposed_endpoint_url_resolution()

s3 = boto3.resource("s3") # uses custom endpoint URL

Endpoint URL resolution order
The core functionality of this package is exposed through the
proposed_endpoint_url_resolution function which sets up the proposed endpoint
resolution order of proposal #230:

endpoint_url keyword argument
import boto3
boto3.resource("s3", endpoint_url="http://localhost:8088")

configuration via service-specific environment variable
configuration via global environment variable
configuration via service sub-sections of the shared configuration file
configuration via global parameter in shared configuration file
fallback to default endpoint determination of botocore

The first truthy value provided by one of the steps will be used as endpoint URL
for the clients and resources, otherwise the resolution continues to the next
step.
Any other endpoint URL resolution order, can be set up using the
custom_endpoint_url_resolution function, with passing the configuration
functions as variadic arguments in the order they should be used.
boto_endpoint_url_shim.custom_endpoint_url_resolution(step1, step2, ..., stepN)

Endpoint URL configuration options
Proposed interface
The proposal #230 includes four main methods for endpoint resolution, two
service-specific endpoint configuration and two global.
This main interface can be set up using proposed_endpoint_url_resolution().
Configuration via service-specific environment variable
Implementation: read_service_env_var.
Read the configuration from environment variables
AWS_<SERVICE_ID>_ENDPOINT_URL in which <SERVICE_ID> is the ServiceId of
the of a specific service as defined in its ServiceModel, transformed with
spaces replaced with underscores and letters upper-cased.
AWS_ENDPOINT_URL_DYNAMODB=http://localhost:8024
AWS_ENDPOINT_URL_ELASTIC_BEANSTALK=http://localhost:8053

Configuration via global environment variable
Implementation: read_global_env_var.
Read the configuration from the global environment variable AWS_ENDPOINT_URL
and use this endpoint URL for all services.
AWS_ENDPOINT_URL=http://localhost:8099

Configuration via service sub-sections of the shared configuration file
Implementation: read_service_config_file.
Read the configuration from the shared configuration file, as the endpoint_url
parameter under the service_id sub-section in the services definition. As
above, service_id is a transform for the ServiceId with spaces replaced with
underscores and letters lower-cased. The services definition to use is
referenced by key in the profile via the services parameter.
[services local-db-eb]
dynamodb =
endpoint_url = http://localhost:8024
elastic_beanstalk =
endpoint_url = http://localhost:8053
[profile testing]
services = local-db-eb

Configuration via global parameter in shared configuration file
Implementation: read_global_config_file.
Read the configuration from the endpoint_url parameter at the top level of a
services definition and use this endpoint URL for all services. The services
definition to use is referenced by key in the profile via the services
parameter.
[services local-services]
endpoint_url = http://localhost:8099
[profile testing]
services = local-services

Alternative interfaces
Several more interfaces are included in the proposal #230, they have been
implemented as functions in this package.
As a convenience, the proposed interface above followed by the global
environment variable and global configuration file methods can be set up using
global_endpoint_url_resolution.
Configuration via mapping in global environment variable
Implementation: read_mapping_env_var.
Read the configuration from the global environment variable AWS_ENDPOINT_URL,
containing a mapping of lower-case service_ids to endpoint URLs.
AWS_ENDPOINT_URL="dynamodb=http://localhost:8024,elastic_beanstalk=http://localhost:8053"

NB. The mapping is loaded once on the first use of the function and cached
for later uses.
Configuration via named top level parameters in shared configuration file
Implementation: read_named_top_level_config_file.
Read the configuration from the <service_id>_endpoint_url parameter at the top
level of a profile, with <service_id> the lower-case service_id.
[profile local-services]
dynamodb_endpoint_url = http://localhost:8024
elastic_beanstalk_endpoint_url = http://localhost:8053

Custom interface
Users are free to define and use functions to obtain the endpoint URL of a
service.
The custom functions must adhere to the following signature:
def func(session: botocore.session.Session, service_id: str) -> str | None: ...

with:

session a botocore.session.Session
service_id the ServiceId of a specific service as defined in its
ServiceModel, transformed with spaces replaced with underscores and letters
lower-cased
returns a str | None either the endpoint URL or None to continue to the
next step in the resolution chain