NAME

Amazon::API - A generic base class for AWS Services

SYNOPSIS

package Amazon::CloudWatchEvents;

use parent qw( Amazon::API );

# subset of methods I need
our @API_METHODS = qw(
 ListRuleNamesByTarget
 ListRules
 ListTargetsByRule
 PutEvents
 PutRule
);

sub new {
  my ($class, %options) = @_;

  $class->SUPER::new(
    service       => 'events',
    api           => 'AWSEvents',
    api_methods   => \@API_METHODS,
    decode_always => 1,
    %options,
  );
}

1;

Then...

my $rules = Amazon::CloudWatchEvents->new->ListRules();

...or

my $rules = Amazon::API->new(
  { service => 'events',
    api     => 'AWSEvents',
  }
)->invoke_api( 'ListRules' );

DESCRIPTION

https://github.com/rlauer6/perl-Amazon-API/actions/workflows/build.yml/badge.svg

Generic class for constructing AWS API interfaces. Typically used as a parent class, but can be used directly. This package can also generates stubs for Amazon APIs using the Botocore project's metadata. (See "BOTOCORE SUPPORT").

See "IMPLEMENTATION NOTES" for using Amazon::API directly to call AWS services.
See Amazon::CloudWatchEvents for an example of how to use this module as a parent class.
See Amazon::API::Botocore::Pod for information regarding how to automatically create Perl classes for AWS services using Botocore metadata.

BACKGROUND AND MOTIVATION

A comprehensive Perl interface to AWS services similar to the Botocore library for Python has been a long time in coming. The PAWS project has been attempting to create an always up-to-date AWS interface with community support. Some however may find that project a little heavy in the dependency department. If you are looking for an extensible (albeit spartan) method of invoking a subset of services with a lower dependency count, you might want to consider Amazon::API.

Think of this class as a DIY kit for invoking only the methods you need for your AWS project. Using the included amazon-api utility however, you can also roll your own complete Amazon API classes that include support for serializing requests and responses based on metadata provided by the Botocore project. The classes you create with amazon-api include full documentation as pod. (See "BOTOCORE SUPPORT" for more details).

NOTE: The original Amazon::API was written in 2017 as a very lightweight way to call a handfull of APIs. The evolution of the module was based on discovering, without much documentation or help, the nature of Amazon APIs. In retrospect, even back then, it would have been easier to consult the Botocore project and decipher how that project managed to create a library from the metadata. Fast forward to 2022 and Amazon::API is now capable of using the Botocore metadata in order to, in most cases, correctly call any AWS service. The Amazon::API module can still be used without the assistance of Botocore metadata, but it works a heckuva lot better with it.

You can use Amazon::API in 3 different ways:

Take the Luddite approach

my $queues = Amazon::API->new(
 {
  service     => 'sqs',
  http_method => 'GET'
 })->invoke_api('ListQueues');

Build your own API classes with just what you need

package Amazon::API::SQS;

use strict;
use warnings;

use parent qw( Amazon::API );

our @API_METHODS = qw(
  ListQueues
  PurgeQueue
  ReceiveMessage
  SendMessage
);

sub new {
  my ( $class, @options ) = @_;
  $class = ref($class) || $class;

  my %options = ref( $options[0] ) ? %{ $options[0] } : @options;

  return $class->SUPER::new(
    { service       => 'sqs',
      http_method   => 'GET',
      api_methods   => \@API_METHODS,
      decode_always => 1,
      %options
    }
  );
}

1;

use Amazon::API::SQS;
use Data::Dumper;

my $sqs = Amazon::API::SQS->new;
print Dumper($sqs->ListQueues);

Use the Botocore metadata to build classes for you

amazon-api -s sqs create-stubs
amazon-api -s sqs create-shapes

perl -I . -MData::Dumper -MAmazon::API:SQS -e 'print Dumper(Amazon::API::SQS->new->ListQueues);'

NOTE: In order to use Botocore metadata you must clone the Botocore repository and point the utility to the repo.

Clone the Botocore project from GitHub:

mkdir ~/git
cd git
git clone https://github.com/boto/botocore.git

Generate stub classes for the API and shapes:

amazon-api -b ~/git/botocore -s sqs -o ~/lib/perl5 create-stubs
amazon-api -b ~/git/botocore -s sqs -o ~/lib/perl5 create-shapes

perldoc Amazon::API::SQS

See Amazon::API::Botocore::Pod for more details regarding building stubs and shapes.

THE APPROACH

Essentially, most AWS APIs are RESTful services that adhere to a common protocol, but differences in services make a single solution difficult. All services more or less adhere to this framework:

1. Set HTTP headers (or query string) to indicate the API and method to be invoked
2. Set credentials in the header
3. Set API specific headers
4. Sign the request and set the signature in the header
5. Optionally send a payload of parameters for the method being invoked

Specific details of the more recent AWS services are well documented, however early services were usually implemented as simple HTTP services that accepted a query string. This module attempts to account for most of the nuances involved in invoking AWS services and provide a fairly generic way of invoking these APIs in the most lightweight way possible.

Using Amazon::API as a generic, lightweight module, naturally does not provide nuanced support for individual AWS services. To use this class in that manner for invoking the AWS APIs, you need to be very familiar with the specific API requirements and responses and be willng to invest time reading the documentation on Amazon's website. The payoff is that you can probably use this class to call any AWS API without installing a large number of dependencies.

If you don't mind a few extra dependencies and overhead, you should generate the stub APIs and support classes using the amazon-api utility. The stubs and shapes produced by the utility will serialize and deserialize requests and responses correctly by using the Botocore metadata. Botocore metadata provides the necessary information to create classes that can successfully invoke all of the Amazon APIs.

A good example of creating a quick and dirty interface to CloudWatch Events can be found here:

Amazon::CloudWatchEvents

And invoking some of the APIs can be as easy as:

Amazon::API->new(
  service     => 'sqs',
  http_method => 'GET'
}
)->invoke_api('ListQueues');

BOTOCORE SUPPORT

A new experimental module ( Amazon::API::Botocore) is now included in this project.

!!CAUTION!!

Support for API calls using the Botocore metadata may be buggy and is subject to change. It may not be suitable for production environments at this time.

Using Botocore metadata and the utilities in this project, you can create Perl classes that simplify calling AWS services. After creating service classes and shape objects from the Botocore metadata calling AWS APIs will look something like this:

use Amazon::API::SQS;

my $sqs = Amazon::API::SQS->new;
my $rsp = $sqs->ListQueues();

The Amazon::API::Botocore module augments Amazon::API by using Botocore metadata for determining how to call individual services and serialize parameters passed to its API methods. A utility (amazon-api) is provided that can generate Perl classes for all AWS services using the Botocore metadata.

Perl classes that represent AWS data structures (aka shapes) that are passed to or returned from services can also be generated. These classes allow you to call all of the API methods for a given service using simple Perl objects that are serialized correctly for a specific method.

Service classes are subclassed from Amazon::API so their new() constructor takes the same arguments as Amazon::API::new().

my $credentials = Amazon::Credential->new();

my $sqs = Amazon::API::SQS->new( credentials => $credentials );

If you are going to use the Botocore support and automatically generate API classes you must also create the data structure classes that are used by each service. The Botocore based APIs will use these classes to serialize requests and responses.

For more information on generating API classes, see Amazon::API::Botocore::Pod.

Response Serialization

With little documentation to go on, interpretting the Botocore metadata and deducing how to serialize Botocore shapes (using a single serializer) from Perl objects has been a difficult task. It's likely that there are still some edge cases and bugs lurking in the serialization methods. Accordingly, starting with version 1.4.5, serialization exceptions or exceptions that occur while attempting to decode a response, will result in the raw response being returned to the caller. The idea being that getting something back that allows you figure out what to do with the response might be better than receiving an error.

OTOH, you might want to see the error, report it, or possibly contribute to its resolution. You can prevent errors from being surpressed by setting the raise_serializtion_errors to a true value. The default is false.

Throughout the rest of this documentation a request made using one of the classes created by the Botocore support scripts will be referred to as a Botocore request or Botocore API.

Starting with version 2.0.12 serialization has become much more reliable, but there are still some differences in the way the Python Botocore library serialize responses. For example, some serializers may include or exclude members that are not present in the response payload. If you are testing a response element, the best approach is to first test the truthiness and then test the presence of content.

if ( $result->{$key} && @{$result->{$key}} ) 

if ( $result->{$key} && %{result->{$key}} )

ERRORS

When an error is returned from an API request, an exception class (Amazon::API::Error) will be raised if raise_error has been set to a true value. Additionally, a detailed error message will be displayed if print_error is set to true.

See Amazon::API::Error for more details.

METHODS AND SUBROUTINES

Reminder: You can mostly ignore this part of the documentation when you are leveraging Botocore to generate your API classes.

new

new(options)

All options are described below. options can be a list of key/values or hash reference.

action

The API method. Normally, you would not set action when you construct your object. It is set when you call the invoke_api method or automatically set when you call one of the API stubs created for you.

Example: 'PutEvents'

api

The name of the AWS service. See "IMPLEMENTATION NOTES" for a detailed explanation of when to set this value.

Example: 'AWSEvents'

api_methods

A reference to an array of method names for the API. The new constructor will automatically create methods for each of the method names listed in the array.

The methods that are created for you are nothing more than stubs that call invoke_api. The stub is a convenience for calling the invoke_api method as shown below.

my $api = Amazon::CloudWatch->new;

$api->PutEvents($events);

...is equivalent to:

$api->invoke_api->('PutEvents', $events);

Consult the Amazon API documentation for the service to determine what parameters each action requires.

aws_access_key_id

Your AWS access key. Both the access key and secret access key are required if either is passed. If no credentials are passed, an attempt will be made to find credentials using Amazon::Credentials. Note that you may need to pass token as well if you are using temporary credentials.

aws_secret_access_key

Your AWS secret access key.

content_type

Default content for parameters passed to the invoke_api() method. If you do not provide this value, a default content type will be selected based on the service's protocol.

query     => application/x-www-form-urlencoded
rest-json => application/x-amz-json-1.1
json      => application/json
rest-xml  => application/xml

credentials (optional)

Accessing AWS services requires credentials with sufficient privileges to make programmatic calls to the APIs that support a service. This module supports three ways that you can provide those credentials.

1. Pass the credentials directly.

Pass the values for the credentials (aws_access_key_id, aws_secaret_access_key, token) when you call the new method. A session token is typically required when you have assumed a role, you are using the EC2's instance role or a container's role.

2. Pass a class that will provide the credential keys.

Pass a reference to a class that has getters for the credential keys. The class should supply getters for all three credential keys.

Pass the reference to the class as credentials in the constructor as shown here:

my $api = Amazon::API->new(credentials => $credentials_class, ... );

3. Use the default Amazon::Credentials class.

If you do not explicitly pass credentials or do not pass a class that will supply credentials, the module will use the Amazon::Credentials class that attempts to find credentials in the environment, your credentials file(s), or the container or instance role. See Amazon::Credentials for more details.

NOTE: The latter method of obtaining credentials is probably the easiest to use and provides the most succinct and secure way of obtaining credentials.

debug

Set debug to a true value to enable debug messages. Debug mode will dump the request and response from all API calls. You can also set the environment variable DEBUG to enable debugging output. Set the debug value to '2' to increase the logging level.

default: false

decode_always

Set decode_always to a true value to return Perl objects from API method calls. The default is to return the raw output from the call. Typically, API calls will return either XML or JSON encoded objects. Setting decode_always will attempt to decode the content based on the returned content type.

default: false

error

The most recent result of an API call. undef indicates no error was encountered the last time invoke_api was called.

http_method

Sets the HTTP method used to invoke the API. Consult the AWS documentation for each service to determine the method utilized. Most of the more recent services utilize the POST method, however older services like SQS or S3 utilize GET or a combination of methods depending on the specific method being invoked.

default: POST

last_action

The last method call invoked.

no_passkey_warning

Prevent passkey warning. This is an option to Amazon::Credentials.

print_error

Setting this value to true enables a detailed error message containing the error code and any messages returned by the API when errors occur.

default: true

protocol

One of 'http' or 'https'. Some Amazon services do not support https (yet).

default: https

raise_error

Setting this value to true will raise an exception when errors occur. If you set this value to false you can inspect the error attribute to determine the success or failure of the last method call.

$api->invoke_api('ListQueues');

if ( $api->get_error ) {
  ...
}

default: true

region

The AWS region. Pass an empty string if the service is a global service that does not require or want a region.

default: $ENV{'AWS_REGION'}, $ENV{'AWS_DEFAULT_REGION'}, 'us-east-1'

response

The HTTP response from the last API call.

service

The AWS service name. Example: sqs. This value is used as a prefix when constructing the the service URL (if not url attribute is set).

service_url_base

Deprecated, use service

token

Session token for assumed roles.

url

The service url. Example: https://events.us-east-1.amazonaws.com

Typically this will be constructed for you based on the region and the service being invoked. However, you may want to set this manually if for example you are using a service like <LocalStack|https://localstack.cloud/> that mocks AWS API calls.

my $api = Amazon::API->new(service => 's3', url => 'http://localhost:4566/');

user_agent

Your own user agent object. Using Furl, if you have it avaiable may result in faster response.

default: LWP::UserAgent

version

Sets the API version. Some APIs require a version. Consult the documentation for individual services.

invoke_api

invoke_api(action, [parameters], [content-type], [headers]);

or using named parameters...

invoke_api({ action => args, ... } )

Invokes the API with the provided parameters.

action

API name.

parameters

Parameters to send to the API. parameters can be a scalar, a hash reference or an array reference. See the discussion below regarding content-type and how invoke_api() formats parameters before sending them as a payload to the API.

You can use the param_n() method to format query string arguments that are required to be in the param.n notation. This is about the best documentation I have seen for that format. From the AWS documentation...

Some actions take lists of parameters. These lists are specified using the param.n notation. Values of n are integers starting from 1. For example, a parameter list with two elements looks like this:

&AttributeName.1=first

&AttributeName.2=second

An example of using this notation is to set queue attributes when creating an SQS queue.

my $attributes = { Attributes => [ { Name => 'VisibilityTimeout', Value => '100' } ] };
my @sqs_attributes= Amazon::API::param_n($attributes);

eval {
  $sqs->CreateQueue([ 'QueueName=foo', @sqs_attributes ]);
};

See "param_n" for more details.

content-type

If you pass the content-type parameter, it is assumed that the parameters are the actual payload to be sent in the request (unless the parameter is a reference).

The parameters will be converted to a JSON string if the parameters value is a hash reference. If the parameters value is an array reference it will be converted to a query string (Name=Value&...).

To pass a query string, you should send an array of key/value pairs, or an array of scalars of the form Name=Value.

[ { Action => 'DescribeInstances' } ]
[ 'Action=DescribeInstances' ]

headers

Array reference of key/value pairs representing additional headers to send with the request.

decode_response

Boolean that indicates whether or not to deserialize the most recent response from an invoked API based on the Content-Type header returned. If there is no Content-Type header, then the method will try to decode it first as a JSON string and then as an XML string. If both of those fail, the raw content is returned.

You can enable or disable deserializing responses globally by setting the decode_always attribute when you call the new constructor.

default: true

By default, `Amazon::API` will retrieve all results for Botocore based API calls that require pagination. To turn this behavior off, set use_paginator to a false value when you instantiate the API service.

my $ec2 = Amazon::API->new(use_paginator => 0);

You can also use the "paginator" method to retrieve all results from Botocore requests that implement pagination.

submit

submit(options)

This method is used internally by invoke_api and normally should not be called by your applications.

options is a reference to a hash of options:

content

Payload to send.

content_type

Content types we have seen used to send values to AWS APIs:

application/json
application/x-amz-json-1.0
application/x-amz-json-1.1
application/x-www-form-urlencoded

Check the documentation for the individual APIs for the correct content type.

headers

Array reference of key/value pairs that represent additional headers to send with the request.

EXPORTED METHODS

get_api_service

get_api_service(api, options)

Convenience routine that will return an API instance.

my $sqs = get_api_service 'sqs';

Equivalent to:

require Amazon::API::SQS;

my $sqs = Amazon::API::SQS->new(%options);

api: The service name. Example: route53, sqs, sns
options: list of key/value pairs passed to the new constructor as options

create_url_encoded_content

create_urlencoded_content(parameters, action, version)

Returns a URL encoded query string. parameters can be any of SCALAR, ARRAY, or HASH. See below.

parameters

SCALAR

Query string to encode (x=y&w=z..)

ARRAY

Can be one of:

Array of hashes where the keys are the query string variable and the value is the value of that variable
Array of strings of the form "x=y"
An array of key/value pairs - qw( x y w z )

HASH

Key/value pairs. If value is an array it is assumed to be a list of hashes

action

The method being called. For some query type APIs an Action query variable is required.

version

The WSDL version for the API. Some query type APIs require a Version query variable.

paginator

paginator(service, api, request)

Returns an array containing the results of an API call that requires pagination,

my $result = paginator($ec2, 'DescribeInstances', { MaxResults => 10 });

param_n

param_n(parameters)

Format parameters in the "param.n" notation.

parameters should be a hash or array reference.

A good example of a service that uses this notation is the SendMessageBatch SQS API call.

The sample request can be found here:

SendMessageBatch

https://sqs.us-east-2.amazonaws.com/123456789012/MyQueue/
?Action=SendMessageBatch
&SendMessageBatchRequestEntry.1.Id=test_msg_001
&SendMessageBatchRequestEntry.1.MessageBody=test%20message%20body%201
&SendMessageBatchRequestEntry.2.Id=test_msg_002
&SendMessageBatchRequestEntry.2.MessageBody=test%20message%20body%202
&SendMessageBatchRequestEntry.2.DelaySeconds=60
&SendMessageBatchRequestEntry.2.MessageAttribute.1.Name=test_attribute_name_1
&SendMessageBatchRequestEntry.2.MessageAttribute.1.Value.StringValue=test_attribute_value_1
&SendMessageBatchRequestEntry.2.MessageAttribute.1.Value.DataType=String
&Expires=2020-05-05T22%3A52%3A43PST
&Version=2012-11-05
&AUTHPARAMS

To produce this message you would pass the Perl object below to param_n():

my $message = {
  SendMessageBatchRequestEntry => [
    { Id          => 'test_msg_001',
      MessageBody => 'test message body 1'
    },
    { Id               => 'test_msg_002',
      MessageBody      => 'test message body 2',
      DelaySeconds     => 60,
      MessageAttribute => [
        { Name  => 'test_attribute_name_1',
          Value =>
            { StringValue => 'test_attribute_value_1', DataType => 'String' }
        }
      ]
    }
  ]
};

CAVEATS

If you are calling an API that does not expect parameters (or all of them are optional and you do not pass a parameter) the default is to pass an empty hash..

$cwe->ListRules();

would be equivalent to...

$cwe->ListRules({});

CAUTION! This may not be what the API expects! Always consult the AWS API for the service you are are calling.

GORY DETAILS

If you using the Botocore APIs you can probably ignore this section.

X-Amz-Target

Most of the newer AWS APIs are invoked as HTTP POST operations and accept a header X-Amz-Target in lieu of the CGI parameter Action to specify the specific API action. Some APIs also want the version in the target, some don't. There is sparse documentation about the nuances of using the REST interface directly to call AWS APIs.

When invoking an API, the class uses the api value to indicate that the action should be set in the X-Amz-Target header. We also check to see if the version needs to be attached to the action value as required by some APIs.

if ( $self->get_api ) {
  if ( $self->get_version) {
    $self->set_target(sprintf('%s_%s.%s', $self->get_api, $self->get_version, $self->get_action));
  }
  else {
    $self->set_target(sprintf('%s.%s', $self->get_api, $self->get_action));
  }

  $request->header('X-Amz-Target', $self->get_target());
}

DynamoDB and KMS seem to be able to use this in lieu of query variables Action and Version, although again, there seems to be a lot of inconsistency (and sometimes flexibility) in the APIs. DynamoDB uses DynamoDB_YYYYMMDD.Action while KMS does not require the version that way and prefers TrentService.Action (with no version). There is no explanation in any of the documentations I have been able to find as to what "TrentService" might actually mean. Again, your best approach is to read Amazon's documentation and look at their sample requests for guidance. You can also look to the Botocore project for information regarding the service. Checkout the service-2.json file within the sub-directory botocore/botocore/data/{api-version}/{service-name} which contains details for each service.

In general, the AWS API ecosystem is very organic. Each service seems to have its own rules and protocol regarding what the content of the headers should be.

As noted, this generic API interface tries to make it possible to use one class Amazon::API as a sort of gateway to the APIs. The most generic interface is simply sending query variables and not much else in the header. Services like EC2 conform to that protocol and can be invoked with relatively little fanfare.

use Amazon::API;
use Data::Dumper;

print Dumper(
  Amazon::API->new(
    service => 'ec2',
    version => '2016-11-15'
  )->invoke_api('DescribeInstances')
);

Note that invoking the API in this fashion, version is required.

For more hints regarding how to call a particular service, you can use the AWS CLI with the --debug option. Invoke the service using the CLI and examine the payloads sent by the botocore library.

Rolling a New API

The Amazon::API class will stub out methods for the API if you pass an array of API method names. The stub is equivalent to:

sub some_api {
  my $self = shift;

  $self->invoke_api('SomeApi', @_);
}

Some will also be happy to know that the class will create an equivalent CamelCase version of the method.

As an example, here is a possible implementation of Amazon::CloudWatchEvents that implements one of the API calls.

package Amazon::CloudWatchEvents;

use parent qw/Amazon::API/;

sub new {
  my ($class, $options) = @_;

  my $self = $class->SUPER::new(
    { %{$options},
      api         => 'AWSEvents',
      service     => 'events',
      api_methods => [qw( ListRules )],
    }
  );

  return $self;
}

Then...

use Data::Dumper;

print Dumper(Amazon::CloudWatchEvents->new->ListRules({}));

Of course, creating a class for the service is optional. It may be desirable however to create higher level and more convenient methods that aid the developer in utilizing a particular API.

Overriding Methods

Because the class does some symbol table munging, you cannot easily override the methods in the usual way.

sub ListRules {
  my $self = shift;
  ...
  $self->SUPER::ListRules(@_)
}

Instead, you should re-implement the method as implemented by this class.

sub ListRules {
  my $self = shift;
  ...
  $self->invoke_api('ListRules', @_);
}

Content-Type

Yet another piece of evidence that suggests the organic nature of the Amazon API ecosystem is their use of different Content-Type headers. Some of the variations include:

application/json
application/x-amz-json-1.0
application/x-amz-json-1.1
application/x-www-form-urlencoded

Accordingly, the invoke_api() method can be passed the Content-Type or will try to make its best guess based on the service protocol. It guesses using the following decision tree:

You can also set the default content type used for the calling service by passing the content_type option to the constructor.

$class->SUPER::new(
  content_type => 'application/x-amz-json-1.1',
  api          => 'AWSEvents',
  service      => 'events'
);

ADDITIONAL HINTS

Bad Request

If you send the wrong headers or payload you're liable to get a 400 Bad Request. You may also get other errors that can be misleading when you send incorrect parameters. When in doubt compare your requests to requests from the AWS CLI using the --debug option.

1. Set the debug option to true to see the request object and the response object from Amazon::API.

2. Excecute the AWS CLI with the --debug option and compare the request and response with that of your calls.
Payloads

Pay attention to the payloads that are required by each service. Do not assume that sending nothing when you have no parameters to pass is correct. For example, the ListSecrets API of SecretsManager requires at least an empty JSON object.
```
$api->invoke_api('ListSecrets', {});
```
Failure to send at least an empty JSON object will result in a 400 response.

VERSION

This documentation refers to version 2.0.13 of Amazon::API.

DIAGNOSTICS

To enable diagnostic output set debug to a true value when calling the constructor. You can also set the DEBUG environment variable to a true value to enable diagnostics.

Logging

By default Amazon::API uses Log::Log4perl's Stealth loggers to log at the DEBUG and TRACE levels. Setting the environment variable DEBUG to some value or passing a true value for debug in the constructor will trigger verbose logging.

If you pass a logger to the constructor, Amazon::API will attempt to use that if it has the appropriate logging level methods (error, warn, info, debug, trace). If Log::Log4perl is unavailable and you do not pass a logger, logging is essentially disabled at any level.

If, for some reason you set the enviroment variable DEBUG to a true value but do not want Amazon::API to log messages you can turn off logging as shown below:

my $ec2 = Amazon::API::EC2->new();

$ec2->set_log_level('fatal');

DEPENDENCIES

...and possibly others.

INCOMPATIBILITIES

BUGS AND LIMITATIONS

This module has not been tested on Windows OS. Please report any issues found by opening an issue here:

https://github.com/rlauer6/perl-Amazon-API/issues

FAQs

Why should I use this module instead of PAWS?

Maybe you shouldn't. PAWS is a community supported project and may be a better choice for most people. The programmers who created PAWS are luminaries in the pantheon of Perl programming (alliteration intended). If you want to use something a little lighter in the dependency department however, and perhaps only need to invoke a single service, Amazon:API may be the right choice.

Does it perform better than PAWS?

Probably. But individual API calls to Amazon services have their own performance characteristics and idiosyncracies. The overhead introduced by this module and PAWS may be insignificant compared to the API performance itself. YMMV.

Does this work for all APIs?

I don't know. Probably not. Would love to hear your feedback. Amazon::API has been developed based on my needs. Although I have tested it on many APIs, there may still be some cases that are not handled properly and I am still deciphering the nuances of flattening, boxing and serializing objects to send to Amazon APIs. The newer versions of this module using Botocore metadata have become increasingly reliable.

Amazon APIs are not created equal, homogenous or invoked in the the same manner. Some accept parameters as a query strings, some parameters are embedded in the URI, some are sent as JSON payloads and others as XML. Content types for payloads are all over the map. Likewise with return values.

Luckily, the Botocore metadata describes the protocols, parameters and return values for all APIs. The Botocore metadata is quite amazing actually. It is used to provide information to the Botocore library for calling any of the AWS services and even for creating documentation!

Amazon::API can use that information for creating the Perl classes that invoke each API but may not interpret the metadata correctly in all circumstances. Bugs almost certainly exist. :-( Did I mention help is welcome?

If you want to use this to invoke S3 APIs, don't. I haven't tried it and I'm pretty sure it would not work anyway. There are modules designed specifically for S3; Amazon::S3, Net::Amazon::S3. Use them.

Do I have to create the shape classes when I generate stubs for a service?

Possibly. If you create stubs manually, then you do not need the shape classes. If you use the scripts provided to create the API stubs using Botocore metadata, then yes, you must create the shapes so that the Botocore API methods know how to serialize requests. Note that you can create the shape stubs using the Botocore metadata while not creating the API services. You might want to do that if you want a lean stub but want the benefits of using the shape stubs for serialization of the parameters.

If you produce your stubs manually and do not create the shape stubs, then you must pass parameters to your API methods that are ready to be serialized by Amazon::API. Creating data structures that will be serialized correctly however is done for you if you use the shape classes. For example, to create an SQS queue using the shape stubs, you can call the CreateQueue API method as describe in the Botocore documentation.

$sqs->CreateQueue(
 { QueueName => $queue_name,
   tags       => { Name => 'my-new-queue' }, { Env => 'dev' },
   Attributes =>  { VisibilityTimeout => 40 }, { DelaySeconds => 60 }
 });

If you do not use the shape classes, then you must pass the arguments in the form that will eventually be serialized in the correct manner as a query string.

$sqs->CreateQueue([
 'QueueName=foo',
 'Attributes.1.Value=100',
 'Attributes.1.Name=VisibilityTimeout',
 'Tag.1.Key=Name',
 'Tag.1.Value=foo',
 'Tag.2.Key=Env',
 'Tag.2.Value=dev'
]);

This code is wonky. Why?

This code has evolved over the years from being ONLY a way to make RESTful calls to Amazon APIs to incorporating the use of the Botocore metadata. It was one person's effort to create a somewhat lightweight interface to a few AWS APIs. As my own needs have changed and my knowledge of AWS services has increased it became obvious that using the Botocore metadata would yield far superior results. Still, I'm grokking the Botocore metadata intuitively without any help. My interpretations may be off. Help? Pull requests welcomed.

How do I pass AWS credentials to the API?

There is a bit of magic here as Amazon::API will use Amazon::Credentials transparently if you do not explicitly pass the credentials object. I've taken great pains to try to make the aforementioned module somewhat useful and secure.

See Amazon::Credentials.

Can I use more than one set of credentials to invoke different APIs?

Yes. See Amazon::Credentials.

OMG! You update this too frequently!

Yeah, there are a lot of bugs. Should I stop fixing them?

Why are you using XML::Simple when it clearly says "DO NOT"?

It's simple. And it seems easier to build than other modules that almost do the same thing.

I tried to use this with XYZ service and it barfed. What do I do?

That's not too surprising. There are several reasons why your call might not have worked. The most likely place for API calls to fail is when serializing requests or serializing results. Enable debugging and see how far the API gets. Report whether the serialization on the request or response failed. If the serialization of the results failed, you can set decode_always to false which will prevent serialization of the result.

You passed bad data

Take a look at the data you passed, how was it serialized and ultimately passed to the API? Setting the debug flag is usually helpful in understanding how requests and responses are serialized.
You didn't read the docs and passed bad data
```
amazon-api -s sqs CreateQueue
```
The serialization of Amazon::API::Botocore::Shape is busted

Serialization output for every class for every API has not been tested. You may find that some API methods return Bad Request or do not serialize the results (or more likely requests) in the manner expected. Requests are serialized based solely on the metadata found in the Botocore project. There lie the clues for each API (protocol, end points, etc) and the models (shapes) for requests and response elements.

Some requests require a query string, some an XML or JSON payload. The Botocore based API classes use the metadata to determine how to send a request and how to interpret the results. This module uses XML::Simple or JSON to parse the results. It then uses the Amazon::API::Botocore::Serializer to turn the parsed results into a Perl object that respresents the response shape. It's likely that this module has bugs and the shapes returned might not exactly match the return response from the aws command line interface version.

What should be returned by an API request method is documented in these modules and Amazon's CLI.
```
perldoc Amazon::API::Botocore::Shape::EC2:DescribeInstancesRequest
```
Make sure you understand what the API request should look like. amazon_api will help illuminate values you should be sending to APIs.
```
amazon-api -s sqs help CreateQueue
```
Additional Details
Some APIs, most notably query protocol APIs like EC2 seem to require special serializers. Looking at the Python implementation of the Botocore library reveals a separate EC2 serializer. This API has no such "hook" for APIs that require a unique intepretation of the Botocore metadata.

You can however create the correct payloads expected by an API and pass those when you make a request. For example, the EC2 DescribeSecurityGroups API accepts a Filter object to filter the results. The Python Botocore signature looks like this:
```
response = client.describe_security_groups(
    Filters=[
        {
            'Name': 'string',
            'Values': [
                'string',
            ]
        },
    ],
    GroupIds=[
        'string',
    ],
    GroupNames=[
        'string',
    ],
    DryRun=True|False,
    NextToken='string',
    MaxResults=123
)
```
That signature provides a convenient way to pass the required parameters to the API. However, when actually passed to the API the payload is serialized into a query string parameter that might look something like:
```
Filter.1.Name=group-name&Filter.1.Value.1=some-value&Action=DescribeSecurityGroups&Version=2016-11-15
```
The Filters object you passed gets serialized into param.n notation as describe earlier in this documentation. Knowing that fact (by looking at the AWS API for DescribeSecurityGroups) and experiencing a failure when sending what should be the correct request to the API using this class, you could send correctly formatted payloads to query protocol APIs like this one.
```
my @filter = param_n(
   { Filter => [
       { Name  => 'group-name',
         Value => ['tbc-ssh-only']
       }
     ]
   }
 );

print Dumper([filter => \@filter]);
```
Would result in:
```
$VAR1 = [
          'filter',
          [
            'Filter.1.Name=group-name',
            'Filter.1.Value.1=tbc-ssh-only'
          ]
        ];
```
Arrays passed to query protocol requests are assumed to be lists of query variables and values and are added to the URL when the request is made.

Hopefully, as more is learned about serializing those kinds of API requests this class will be able to successfully make those API calls.

UPDATE: Try using the Botocore protocol for APIs by passing a hash reference of expected variables first. Recent updates have been made to create special serializers for these older query protocol APIs.
If you find this project's serializer deficient, please log an issue and I will attempt to address it.

LICENSE AND COPYRIGHT

This module is free software. It may be used, redistributed and/or modified under the same terms as Perl itself.

SEE OTHER

Amazon::Credentials, Amazon::API::Error, AWS::Signature4, Amazon::API::Botocore

AUTHOR

Rob Lauer - <rlauer6@comcast.net>

To install Amazon::API, copy and paste the appropriate command in to your terminal.

cpanm

cpanm Amazon::API

CPAN shell

perl -MCPAN -e shell
install Amazon::API

For more information on module installation, please visit the detailed CPAN module installation guide.

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NAME

SYNOPSIS

DESCRIPTION

BACKGROUND AND MOTIVATION

THE APPROACH

BOTOCORE SUPPORT

Response Serialization

ERRORS

METHODS AND SUBROUTINES

new

invoke_api

decode_response

submit

EXPORTED METHODS

get_api_service

create_url_encoded_content

paginator

param_n

CAVEATS

GORY DETAILS

X-Amz-Target

Rolling a New API

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Content-Type

ADDITIONAL HINTS

VERSION

DIAGNOSTICS

Logging

DEPENDENCIES

INCOMPATIBILITIES

BUGS AND LIMITATIONS

FAQs

Why should I use this module instead of PAWS?

Does it perform better than PAWS?

Does this work for all APIs?

Do I have to create the shape classes when I generate stubs for a service?

This code is wonky. Why?

How do I pass AWS credentials to the API?

Can I use more than one set of credentials to invoke different APIs?

OMG! You update this too frequently!

Why are you using XML::Simple when it clearly says "DO NOT"?

I tried to use this with XYZ service and it barfed. What do I do?

LICENSE AND COPYRIGHT

SEE OTHER

AUTHOR

Module Install Instructions