Open Stack

Unless anybody has major concerns, I'm going to push this into Gerrit for further technical discussion and review.

Jamie

From: Jamie Hannaford <jamie.hannaford at rackspace.com<mailto:jamie.hannaford at rackspace.com>>
Reply-To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Date: Wednesday, April 30, 2014 at 7:09 PM
To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Cc: "sam.choi at hp.com<mailto:sam.choi at hp.com>" <sam.choi at hp.com<mailto:sam.choi at hp.com>>
Subject: [openstack-dev] [openstack-php-sdk] Transport layer work


Hey everyone,

So I've been working on the transport layer today and wanted to run some thing past everyone to make sure we're all on the same page. There's no new major new work: just tweeking some existing stuff and moving functionality into new files where I thought it would make things clearer.

1. Minor updates `ClientInterface`

I agree with Matt: we need to keep this interface as simple as possible for new client classes to implement. There's two discrete pieces of functionality the interface should care about: requests and configuration. Here's an outline of what I thought might work:

https://gist.github.com/jamiehannaford/01bbf366f5f3da07bbcd

I tried to keep things as simple as possible - can people lend me their thoughts on it?

One of the main differences with the current version is that it separates out the process of creating a request from sending it. Right now we do it in one method, which is disadvantageous for two reasons:

1. It prevents users from modifying the Request object before sending it. Matt raised a very good point that you can pass in extra headers, etc. into the signature itself - but what I'm talking about is things like event subscribers. In the lifecycle of a cURL transaction (a Request being created, prepared, and sent; a response being parsed, etc.) different events are emitted. These events are incredibly useful and empowering for end-users because they enable people to add in their own custom logic to processes which are usually unavailable (unless you actually extend the SDK code). By having a "createRequest" method that actually returns a Request rather than just sending it, we're allowing users to add their own subscribers. Here are a few use-cases: a user might want to add a subscriber which logs everything for that 1 request; a user might want to use a subscriber to handle exceptions differently for that 1 request; a user might want to retry the Request if a particular status code is returned, etc.

2. Most common HTTP frameworks, like Guzzle and ZF2, use these two methods ("createRequest" and "send"). It makes sense to stick with convention so end-users and contributors are not confused.


2. Moving Guzzle stuff to a sub-directory

Right now we're using Guzzle by default, but we also want to support the ability for users to inject their own HTTP client in. So to make this clearer, I've moved Guzzle-specific files to their own "Guzzle" sub-directory (under the OpenStack\Common\Transport\Guzzle namespace). I've also changed the "GuzzleClient" classname to "GuzzleAdapter" because it's actually adapting an existing client, not serving as one. All it's doing is wrapping Guzzle and implementing our standard interface - so I wanted to make that clearer and avoid confusion.


3. HTTP exceptions

I also discovered a really cool way to handle exceptions. Right now, we're throwing exceptions in the adapter - which adds a lot of exception-specific logic to a base class. So instead, I copied all of this existing logic to a new "RequestException" class. All the GuzzleClient/GuzzleAdapter needs to do is call RequestException::create($request, $response) and all of the logic for finding the right class for the right HTTP status code is determined inside RequestException like this:

https://gist.github.com/jamiehannaford/0a085d4b1507308b0190

Another thing I wanted to do is make it easier for devs to debug the problem once an exception is thrown - so I made the Request and Response objects (for a failed request) available in the exception. So instead of printing out a generic message, we also allow them the ability to retrieve the offending request/response with $e->getRequest() and $e->getResponse()

---

That's about it, basically :)

Does anybody have any questions or concerns with any of this?

Jamie



Jamie Hannaford
Software Developer III - CH     [experience Fanatical Support]

Tel:    +41434303908
Mob:    +41791009767
        [Rackspace]




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Jamie Hannaford
Software Developer III - CH     [experience Fanatical Support]

Tel:    +41434303908
Mob:    +41791009767
        [Rackspace]



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This e-mail message (including any attachments or embedded documents) is intended for the exclusive and confidential use of the individual or entity to which this message is addressed, and unless otherwise expressly indicated, is confidential and privileged information of Rackspace. Any dissemination, distribution or copying of the enclosed material is prohibited. If you receive this transmission in error, please notify us immediately by e-mail at abuse at rackspace.com and delete the original message. Your cooperation is appreciated.
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