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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: [email protected]: JLMARTIN
CAPSiDETwitter: @capsideMail: [email protected]