"Perl was lacking a complete SDK for all of AWSs' services. Now that Paws has been released to CPAN, come to hear how to use it, how it came to be, what you can expect, and how you can contribute." Talk profile page at the YAPC Europe 2015 conference: http://act.yapc.eu/ye2015/talk/6196

1. Paws – A Perl AWS SDK
@pplu_io
03/09/2015 - Granada
YAPC::EU 2015
Jose Luis Martinez

2. AWS is…
• Cloud Computing
• Consume computing/database/queuing/etc services via an API
• Everything is an API 

3. AWS is…
Programmers wet dream

4. Why?
Isn’t there support for AWS on CPAN?

5. AWS Services on CPAN
• There are a LOT
• EC2, SQS, S3, RDS, DynamoDB, etc
• But lots are were missing
• AWS::CLIWrapper is a generic solution too
• Shells off to the oficial AWS CLI (python)
I want Perl support for ALL of them

6. Different authors, different opinions
• Default region (eu-west-1 for some, us-east-1 for others)
• Different HTTP clients
• LWP, HTTP::Tiny, Furl, etc
I want explicit, required, region. Croak if not specified
Pluggable HTTP client?

9. Different authors, different photo
• Some regions not supported due to bugs
• Subtle name changes in region endpoints
• Credential handling
• Module just covers their needs
I want as broad support as we can get

10. Credential handling
• Roles in AWS help you not have to distribute credentials (AccessKey
and SecretKey)
• Support depends on author of module knowing of them / needing them
I want support for Instance Roles, STS AssumeRole, Federation for all
services

11. UpToDate-ness
• Being up to date depends on authors needs, time, etc
• AWS APIs are updated a lot
I want up to date APIs

12. Lets write an SDK!

14. Some numbers
52 services

15. Some numbers
52 services
~1600 actions

16. Some numbers
52 services
~1600 actions
~3700 distinct input/output objects

17. Some numbers
52 services
~1600 actions
~3700 distinct input/output objects
~12000 attributes

19. Write by hand?

20. Write by hand?

21. Paws is autogenerated

23. Paws is autogenerated
• AWS has some JSON definition files in their SDKs (data-driven)
• Pick them up to generate classes for:
• Actions
• Inputs to actions (parameters)
• Outputs from actions (outputs)
• HTML documentation -> POD
make gen-classes

25. Code generators
• In builder-lib (not distributed on CPAN)
• Paws::API::Builder
• Paws::API::Builder::EC2
• Paws::API::Builder::query
• Paws::API::Builder::json
• Paws::API::Builder::restjson
• Paws::API::Builder::restxml
• Leaves all auto-generated code in auto-lib (distributed on CPAN)
• Hand-written code is in lib
Note: this is not needed if you only want to use Paws. This is intended for developers. We’ll see more internals later 

26. Using Paws

27. Each AWS API is a “Service Class”
• Each Action in the API is a method on the Service Class
• EC2 API -> Paws::EC2 service class
• Paws::EC2 objects have methods like
• RunInstances
• TerminateInstances
• DescribeInstances

28. How do I get an instance of a service
class?
use Paws;
my $ec2 = Paws->service(‘EC2’, region => ‘eu-west-1’);
my $iam = Paws->service(‘IAM’);
# $ec2 and $iam are instances of Paws::EC2 and
Paws::IAM
# they use Paws default config (they just work )

29. How do I get an instance of a service
class? (II)
my $paws = Paws->new(config => {
region => ‘eu-west-1’,
caller => ‘Paws::Net::LWPCaller’,
credentials => ‘My::Custom::Credential::Provider’
});
my $ec2 = $paws->service(‘EC2’);
# ec2 is bound to region ‘eu-west-1’
# and called with LWP
# and gets it’s credentials from some custom source

30. Calling a method
$ec2->Method1(
Param1 => ‘Something’,
Param2 => 42,
Complex1 => {
x => 1,
y => 2,
z => 3
},
Complex2 => [
{ x => 1, y => 2 },
{ x => 2, y => 3 }
])

31. Calling a method
$ec2->Method1(
Param1 => ‘Something’,
Param2 => 42,
Complex1 => {
x => 1,
y => 2,
z => 3
},
Complex2 => [
{ x => 1, y => 2 },
{ x => 2, y => 3 }
])
Docs tell you that this is a Paws::Service::XXX object, but you don’t have
to instance it !!!
Just pass the attributes and the values as a hashref 

32. Calling a method: maps
• Arbitrary key/value pairs
• Don’t build an object either. Paws will handle it for you
• $ec2->Method1(
Map1 => {
x => 1,
y => 2,
z => 3
});

33. Methods return objects
my $object = $x->Method1(…)
Method1 returns Paws::Service::Method1Result
has ‘X’, has ‘Y’, has ‘Complex’ => (isa => ‘Paws::Service::Complex1’)
$object->X
$object->Complex->Complex1Attribute

34. Tricks

35. Tricks: CLI
• Paws ships with a CLI
paws SERVICE --region xx-east-1 DescribeFoo Arg1 Val1
Uses ARGV::Struct to convey nested datastructures via command line

36. Tricks: open_aws_console
• Opens a browser with the AWS console (using the SignIn service)
• Uses your current credentials (extends a temporary token)

37. Tricks: Changing endpoints
my $predictor = $paws->service('ML', region_rules =>
[ { uri => $endpoint_url } ]);
• Works for any service: SQS, EC2…

38. Tricks: Credential providers
• Default one tries to behave like AWS SDKs
• Environment (AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY)
• File (~/.aws/credentials, an ini file)
• From the metadata service (Instance Roles)
• Your own
• Just attach Role “Paws::Credential” and get the credentials from wherever

39. Internals
Note: actual implementation as of Sept 2015
Read the code / changelog to get a hold of changes

41. Each method has parameters
• Parameters are converted into Moose objects for validation
package Paws::EC2
sub Method(Param1 => Str, Param2 => Int)
Coerces its @_ into Paws::EC2::Method (has ‘Param1’, has
‘Param2’)
Note: not using Moose coercion. Using new_with_coercions

42. Each method has parameters
• Parameters are converted into Moose objects for validation
package Paws::EC2
sub Method(Param3 => Complex1)
Complex1 has it’s own “input class”
Paws::EC2::Complex1 has [‘X’, ‘Y’, ‘Z’ ]
new_with_coercions knows how to coerce { x => 1, y => 2, z => 3 }
into a Paws::EC2::Complex1

43. After coercing parameters into an object
• $self->caller->do_call($self, $call_object)
• Service classes have a “caller”. Caller is defined when constructing the
service object.
• Callers are responsable for
• Getting a Paws::Net::APIRequest (via prepare_request_for_call)
• Prepare_request_for_call is specialized for each type of service in Paws::Net::*Caller roles
• Doing I/O
• Paws::Net::Caller uses HTTP::Tiny (Paws default)
• Paws::Net::LWPCaller uses LWP (contributed)
• Paws::Net::MojoAsyncCaller uses Mojo::UserAgent (experimental)
• Passing results to handle_response

44. Call Object to APIRequest
(prepare_request_for_call)
• Looks in the call object where it has to place parameters to the API
• Headers
• In a serialized body
• JSON
• Query Parameters
• Arrays get coded in f(x) of the API
• att.0=xxx
• att.members.0=xxx
• In the body
• In the URL (REST APIs)
• Signs the request (via roles that know how to sign for that service)

45. handle_response
• Takes a look if there were error conditions in the HTTP call
• Future: should determine how to retry
• Deserializes the response
• XML
• JSON
• Deserializes into objects
• Note: sometimes decides it wants an exception
• Doesn’t throw: just creates an exception object

46. Callers
• Do the IO
• Have to handle some common logic (still)
• Asyc callers don’t need to return the result immediately
• The experimental Mojo caller returns a Future 
• The future fails if the result was an exception

47. Future

49. Future (hint: help needed and accepted)
• Testing Async stuff
• Retrying
• Some APIs return temporary failures
• Want automatic exponential backoff with jitter
• Paging
• Some APIs return paged results
• Want a “give me all of them”
• Waiters
• Wait until some condition is met
• Want a call to wait until Instance is in running state
• A lot more: take a look at GitHub issues

50. Future (hint: help needed and accepted)
• Object Oriented results
• $ec2->TerminateInstances(InstanceIds => [ ‘i-12345678’ ])
• $instance->Terminate
• Special properties
• En/Decode base64, URIescape, etc
• Better access to ArrayRefs
• Use ArrayRef Moose trait for
• Number of elements
• Get element i
• Get list of elements

51. Future (hint: help needed and accepted)
• Refactoring generator clases
• MooseX::DataModel
• Template::Toolkit
• Split Paws into separately instalable modules
• Rinse and Repeat
• For other APIs
• AWS API as a Service

52. Support for APIs
0
5
10
15
20
25
30
35
40
45
50
REST Plain
Types of APIs
Query+XML JSON EC2

53. Support for APIs
0
5
10
15
20
25
30
35
40
45
50
REST Plain
Types of APIs
Query+XML JSON EC2
Implemented

54. Support for APIs
0
5
10
15
20
25
30
35
40
45
50
REST Plain
Types of APIs
Query+XML JSON EC2
Implemented
Need love and testing
S3 not working
Route53?
Lambda?
…

55. Fork your heart out
https://github.com/pplu/aws-sdk-perl/
Contact me:
Twitter: @pplu_io
Mail: joseluis.martinez@capside.com
CPAN: JLMARTIN
CAPSiDE
Twitter: @capside
Mail: hello@capside.com