# erlcloud: AWS APIs library for Erlang
[](https://github.com/erlcloud/erlcloud/actions/workflows/ci.yml)
[](https://hex.pm/packages/erlcloud)
[](COPYRIGHT)
This library is not developed or maintained by AWS thus lots of functionality
is still missing comparing to [aws-cli](https://aws.amazon.com/cli/) or
[boto](https://github.com/boto/boto). Required functionality is being added
upon request.
Service APIs implemented:
- Amazon Elastic Compute Cloud (EC2)
- Amazon EC2 Container Service (ECS)
- Amazon Simple Storage Service (S3)
- Amazon Simple Queue Service (SQS)
- Amazon SimpleDB
- Amazon Mechanical Turk
- Amazon CloudWatch (MON)
- Amazon CloudSearch
- Amazon Inspector
- Amazon Key Management Service (KMS)
- Amazon DirectConnect
- Amazon DynamoDB & DDB streams (ddb2)
- Amazon Autoscaling (AS)
- Amazon CloudTrail (CT)
- Cloud Formation (CFN)
- Config
- ElasticLoadBalancing (ELB)
- Identity and Access Management (IAM)
- Kinesis
- Glue (Catalog table, Crawlers and Job APIs support)
- Athena
- Step Functions (SF)
- CloudWatch
- MechanicalTurk
- Simple DB (SDB)
- Relational Data Service (RDS)
- Simple Email Service (SES)
- Short Token Service (STS)
- Simple Notification Service (SNS)
- Web Application Firewall (WAF)
- AWS Cost and Usage Report API
- AWS Secrets Manager
- AWS Systems Manager (SSM)
- and more to come
The majority of API functions have been implemented. Not all functions have
been thoroughly tested, so exercise care when integrating this library into
production code. Please send issues and patches.
The libraries can be used two ways. You can:
- specify configuration parameters in the process dictionary. Useful for simple
tasks, or
- create a configuration object and pass that to each request as the final
parameter. Useful for Cross AWS Account access
## Roadmap
Below is the library roadmap update along with regular features and fixes.
- 3.0.X
- ~~Remove R16 support~~ __done__
- Support maps
- 3.X.X
- Fix dialyzer findings and make it mandatory for the library
- Only SigV4 signing and generalised in one module. Keep SigV2 in SBD section only
- No more `erlang:error()` use and use of regular tuples as error API.
Breaking change.
### Major API compatibility changes between 0.13.X and 2.0.x
- ELB APIs
- ... list to be filled shortly
### Supported Erlang versions
At the moment we support the following OTP releases:
- 19.3
- 20.3
- 21.3
- 22.3
- 23.3
- 24.3
- 25.3
- 26.2
- 27.1
This list is determined by ensuring eunit tests and dialyzer checks succeed for these versions, but not all of these
versions are in active use by library authors. Please report any issues discovered in actual use.
The Github Actions test runners only support OTP 24+ due to runtime issues, but OTP 19-23 were tested locally with unmodified,
official [Erlang docker images](https://hub.docker.com/_/erlang). Dialyzer checks run against the latest hex-published hackney
for OTP 24+, but a previous versions of hackney (1.15.0) and its dependency parse_trans (3.2.0) were used to do dialyzer checks
for OTP 19-23 due to newer versions of parse_trans requiring OTP 21+.
## Getting started
You need to clone the repository and download rebar/rebar3 (if it's not already
available in your path).
```sh
git clone https://github.com/erlcloud/erlcloud.git
cd erlcloud
wget https://s3.amazonaws.com/rebar3/rebar3
chmod a+x rebar3
```
To compile and run erlcloud:
```sh
make
make run
```
To use erlcloud in your application, add it as a dependency in your
application's configuration file. erlcloud is also available as a [Hex](https://hex.pm) package, refer to the Hex [`mix` usage docs](https://hex.pm/docs/usage) or [`rebar3` usage docs](https://hex.pm/docs/rebar3-usage) for more help including dependencies using Hex syntax.
To use erlcloud in the shell, you can start
it by calling:
```erlang
application:ensure_all_started(erlcloud).
```
### Using Temporary Security Credentials
When access to AWS resources is managed through [third-party identity
providers](http://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_create_for-idp.html)
it is performed using [temporary security
credentials](http://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_temp_use-resources.html).
You can provide your AWS credentials in OS environment variables
```sh
export AWS_ACCESS_KEY_ID=<Your AWS Access Key>
export AWS_SECRET_ACCESS_KEY=<Your AWS Secret Access Key>
export AWS_SESSION_TOKEN=<Your AWS Security Token>
export AWS_DEFAULT_REGION=<Your region>
```
If you did not provide your AWS credentials in the OS environment variables,
then you need to provide configuration read from your profile:
```erlang
{ok, Conf} = erlcloud_aws:profile().
erlcloud_s3:list_buckets(Conf).
```
Or you can provide them via `erlcloud` application environment variables.
```erlang
application:set_env(erlcloud, aws_access_key_id, "your key"),
application:set_env(erlcloud, aws_secret_access_key, "your secret key"),
application:set_env(erlcloud, aws_security_token, "your token"),
application:set_env(erlcloud, aws_region, "your region"),
```
### Using Access Key
You can provide your AWS credentials in environmental variables.
```sh
export AWS_ACCESS_KEY_ID=<Your AWS Access Key>
export AWS_SECRET_ACCESS_KEY=<Your AWS Secret Access Key>
```
If you did not provide your AWS credentials in the environment variables, then
you need to provide the per-process configuration:
```erlang
erlcloud_ec2:configure(AccessKeyId, SecretAccessKey [, Hostname]).
```
Hostname defaults to non-existing `"ec2.amazonaws.com"` intentionally to avoid
mix with US-East-1 Refer to
[aws_config](https://github.com/erlcloud/erlcloud/blob/master/include/erlcloud_aws.hrl)
for full description of all services configuration.
Configuration object usage:
```erlang
EC2 = erlcloud_ec2:new(AccessKeyId, SecretAccessKey [, Hostname])
erlcloud_ec2:describe_images(EC2).
```
### aws_config
The [aws_config](https://github.com/erlcloud/erlcloud/blob/master/include/erlcloud_aws.hrl)
record contains many valuable defaults, such as protocols and ports for AWS
services. You can always redefine them by making new `#aws_config{}` record and
changing particular fields, then passing the result to any `erlcloud` function.
But if you want to change something in runtime this might be tedious and/or not
flexible enough.
An alternative approach is to set default fields within the `app.config ->
erlcloud -> aws_config` section and rely on the config, used by all functions
by default.
Example of such `app.config`:
```erlang
[
{erlcloud, [
{aws_config, [
{s3_scheme, "http://"},
{s3_host, "s3.example.com"}
]}
]}
].
```
### VPC endpoints
If you want to utilise AZ affinity for VPC endpoints you can configure those in
application config via:
```erlang
{erlcloud, [
{services_vpc_endpoints, [
{<<"sqs">>, [<<"myAZ1.sqs-dns.amazonaws.com">>, <<"myAZ2.sqs-dns.amazonaws.com">>]},
{<<"kinesis">>, {env, "KINESIS_VPC_ENDPOINTS"}}
]}
]}
```
Two options are supported:
- explicit list of Route53 AZ endpoints
- OS environment variable (handy for ECS deployments). The value of the
variable should be of comma-separated string like
`"myAZ1.sqs-dns.amazonaws.com,myAZ2.sqs-dns.amazonaws.com"`
Upon config generation, `erlcloud` will check the AZ of the deployment and
match it to one of the pre-configured DNS records. First match is used and if
not match found default is used.
## Basic use
Then you can start making API calls, like:
```erlang
erlcloud_ec2:describe_images().
% list buckets of Account stored in config in process dict
% of of the account you are running in.
erlcloud_s3:list_buckets().
erlcloud_s3:list_buckets(erlcloud_aws:default_cfg()).
% List buckets on 3d Account from Conf
erlcloud_s3:list_buckets(Conf).
```
Creating an EC2 instance may look like this:
```erlang
start_instance(Ami, KeyPair, UserData, Type, Zone) ->
Config = #aws_config{
access_key_id = application:get_env(aws_key),
secret_access_key = application:get_env(aws_secret)
},
InstanceSpec = #ec2_instance_spec{image_id = Ami,
key_name = KeyPair,
instance_type = Type,
availability_zone = Zone,
user_data = UserData},
erlcloud_ec2:run_instances(InstanceSpec, Config).
```
For usage information, consult the source code and
[GitHub repo](https://hexdocs.pm/erlcloud). For detailed API description refer
to the AWS references at:
- [AmazonEC2](http://docs.aws.amazon.com/AWSEC2/latest/APIReference/Welcome.html)
- [Amazon S3](http://docs.aws.amazon.com/AmazonS3/latest/API/Welcome.html)
- and [other services](https://aws.amazon.com/documentation/)
## Notes
Indentation in contributions should follow indentation style of surrounding
text. In general it follows default indentation rules of official erlang-mode
as provided by OTP team.
## Best Practices
- All interfaces should provide a method for working with non-default config.
- Public interfaces with paging logic should prefer `{ok, Results, Marker}`
style to the `{{paged, Marker}, Results}` found in some modules.
In case of records output, tokens should be part of the record.
- Passing next page `NextToken`, `NextMarker` is preferred with `Opts` rather
than a fun parameter like found in many modules.
- Public interfaces should normally expose proplists over records. All new
modules are preferred to have both.
- Exposed records are to be used only for complex outputs. Examples to follow:
ddb2, ecs.
- Library should not expose any long running or stateful processes - no
gen_servers, no caches and etc.
## Publishing to hex.pm
erlcloud is available as a [Hex](https://hex.pm) package. A new version of the package can be published by maintainers using mix or rebar3. A `hex-publish` make target that uses rebar3 is provided for maintainers to use or reference when publishing a new version of the package.
Github Actions will eventually be used to automatically publish new versions.
