Paws – A Perl AWS SDK

@pplu_io

03/09/2015 - Granada

YAPC::EU 2015

Jose Luis Martinez

AWS is…• Cloud Computing• Consume computing/database/queuing/etc services via

an API• Everything is an API

AWS is…

Programmers wet dream

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

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

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 specifiedPluggable HTTP client?

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

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

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

I want up to date APIs

Lets write an SDK!

Some numbers52 services

Some numbers52 services

~1600 actions

Some numbers52 services

~1600 actions

~3700 distinct input/output objects

Some numbers52 services

~1600 actions

~3700 distinct input/output objects

~12000 attributes

Write by hand?

Write by hand?

Paws is autogenerated

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

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

Using Paws

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

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 )

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

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 } ])

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

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 });

Methods return objectsmy $object = $x->Method1(…)

Method1 returns Paws::Service::Method1Result has ‘X’, has ‘Y’, has ‘Complex’ => (isa => ‘Paws::Service::Complex1’)

$object->X$object->Complex->Complex1Attribute

Tricks

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

Tricks: open_aws_console• Opens a browser with the AWS console (using the SignIn

service)• Uses your current credentials (extends a temporary

token)

Tricks: Changing endpointsmy $predictor = $paws->service('ML', region_rules => [ { uri => $endpoint_url } ]);

• Works for any service: SQS, EC2…

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

InternalsNote: actual implementation as of Sept 2015

Read the code / changelog to get a hold of changes

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

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

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

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)

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

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

Future

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

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

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

Support for APIs

REST Plain05

101520253035404550

Types of APIs

Query+XML JSON EC2

Support for APIs

REST Plain05

101520253035404550

Types of APIs

Query+XML JSON EC2

Implemented

Support for APIs

REST Plain05

101520253035404550

Types of APIs

Query+XML JSON EC2

Implemented

Need love and testing

S3 not workingRoute53?Lambda?

…

Fork your heart outhttps://github.com/pplu/aws-sdk-perl/

Contact me:

Twitter: @pplu_ioMail: joseluis.martinez@capside.comCPAN: JLMARTIN

CAPSiDETwitter: @capsideMail: hello@capside.com