[openstack-dev] [pecan] [WSME] Different content-type in request and response

Doug Hellmann doug at doughellmann.com
Thu Dec 18 16:59:24 UTC 2014


On Dec 18, 2014, at 2:53 AM, Renat Akhmerov <rakhmerov at mirantis.com> wrote:

> Doug,
> 
> Sorry for trying to resurrect this thread again. It seems to be pretty important for us. Do you have some comments on that? Or if you need more context please also let us know.

WSME has separate handlers for JSON and XML now. You could look into adding one for YAML. I think you’d want to start looking in http://git.openstack.org/cgit/stackforge/wsme/tree/wsme/rest

By default WSME is going to want to encode the response in the same format as the inputs, because it’s going to expect the clients to want that. I’m not sure how hard it would be to change that assumption, or whether the other WSME developers would really think it’s a good idea.

Doug

> 
> Thanks
> 
> Renat Akhmerov
> @ Mirantis Inc.
> 
> 
> 
>> On 27 Nov 2014, at 17:43, Renat Akhmerov <rakhmerov at mirantis.com> wrote:
>> 
>> Doug, thanks for your answer! 
>> 
>> My explanations below..
>> 
>> 
>>> On 26 Nov 2014, at 21:18, Doug Hellmann <doug at doughellmann.com> wrote:
>>> 
>>> 
>>> On Nov 26, 2014, at 3:49 AM, Renat Akhmerov <rakhmerov at mirantis.com> wrote:
>>> 
>>>> Hi,
>>>> 
>>>> I traced the WSME code and found a place [0] where it tries to get arguments from request body based on different mimetype. So looks like WSME supports only json, xml and “application/x-www-form-urlencoded”.
>>>> 
>>>> So my question is: Can we fix WSME to also support “text/plain” mimetype? I think the first snippet that Nikolay provided is valid from WSME standpoint.
>>> 
>>> WSME is intended for building APIs with structured arguments. It seems like the case of wanting to use text/plain for a single input string argument just hasn’t come up before, so this may be a new feature.
>>> 
>>> How many different API calls do you have that will look like this? Would this be the only one in the API? Would it make sense to consistently use JSON, even though you only need a single string argument in this case?
>> 
>> We have 5-6 API calls where we need it.
>> 
>> And let me briefly explain the context. In Mistral we have a language (we call it DSL) to describe different object types: workflows, workbooks, actions. So currently when we upload say a workbook we run in a command line:
>> 
>> mistral workbook-create my_wb.yaml
>> 
>> where my_wb.yaml contains that DSL. The result is a table representation of actually create server side workbook. From technical perspective we now have:
>> 
>> Request:
>> 
>> POST /mistral_url/workbooks
>> 
>> {
>>   “definition”: “escaped content of my_wb.yaml"
>> }
>> 
>> Response:
>> 
>> {
>>   “id”: “1-2-3-4”,
>>   “name”: “my_wb_name”,
>>   “description”: “my workbook”,
>>   ...
>> }
>> 
>> The point is that if we use, for example, something like “curl” we every time have to obtain that “escaped content of my_wb.yaml” and create that, in fact, synthetic JSON to be able to send it to the server side.
>> 
>> So for us it would be much more convenient if we could just send a plain text but still be able to receive a JSON as response. I personally don’t want to use some other technology because generally WSME does it job and I like this concept of rest resources defined as classes. If it supported text/plain it would be just the best fit for us.
>> 
>>>> 
>>>> Or if we don’t understand something in WSME philosophy then it’d nice to hear some explanations from WSME team. Will appreciate that.
>>>> 
>>>> 
>>>> Another issue that previously came across is that if we use WSME then we can’t pass arbitrary set of parameters in a url query string, as I understand they should always correspond to WSME resource structure. So, in fact, we can’t have any dynamic parameters. In our particular use case it’s very inconvenient. Hoping you could also provide some info about that: how it can be achieved or if we can just fix it.
>>> 
>>> Ceilometer uses an array of query arguments to allow an arbitrary number.
>>> 
>>> On the other hand, it sounds like perhaps your desired API may be easier to implement using some of the other tools being used, such as JSONSchema. Are you extending an existing API or building something completely new?
>> 
>> We want to improve our existing Mistral API. Basically, the idea is to be able to apply dynamic filters when we’re requesting a collection of objects using url query string. Yes, we could use JSONSchema if you say it’s absolutely impossible to do and doesn’t follow WSME concepts, that’s fine. But like I said generally I like the approach that WSME takes and don’t feel like jumping to another technology just because of this issue.
>> 
>> Thanks for mentioning Ceilometer, we’ll look at it and see if that works for us.
>> 
>> Renat
> 
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