Service dependencies specification #488

fmui · 2018-04-03T14:38:06Z

See issue #427.

First draft of the service dependencies specification.

cfdreddbot · 2018-04-03T14:38:10Z

Hey fmui!

Thanks for submitting this pull request! I'm here to inform the recipients of the pull request that you and the commit authors have already signed the CLA.

mhrivnak · 2018-04-03T17:12:22Z

spec.md

+      "service_name": "mysql",
+      "plan_id": "1b367d58-6f17-4cb3-9ef8-3a69e752b826",
+      "plan_name": "small",
+      "credentials": {


Since this contains a binding, why not call the key binding? The word credentials doesn't communicate that other things besides credentials can exist in the object (as we see in this example), which I suspect is why the word binding was chosen for the API.

n3wscott · 2018-04-04T17:46:42Z

spec.md

+* Instance dependencies declare dependencies to a specific instance either
+  by a service instance ID or by a service instance alias.
+
+Dependencies are injected as parameters when a service instance is provisioned.


injected

this makes it sound like there is magic happening, these are not just provided in the provision request?

n3wscott · 2018-04-04T17:50:31Z

spec.md

+Dependencies are declared in the catalog at the plan level.
+There are three types of dependencies.
+
+* Open dependencies are arbitrary dependencies.


an "open dependency" sounds like it should be an unfulfilled dependency, ie: the service requests a dependency of some type. This is really a platform defined dependency or something along that line.

n3wscott · 2018-04-04T17:52:39Z

spec.md

+
+| Field | Type | Description |
+| --- | --- | --- |
+| open\_dependencies\_parameter | string | A parameter name used for an open list of dependencies. |


I think this should be "open_dependencies_field" to mean the field name the broker expects this list to be in.

Also: if it is a list, make it a list?

n3wscott · 2018-04-04T17:53:25Z

spec.md

+
+| Field | Type | Description |
+| --- | --- | --- |
+| parameter* | string | Name of the parameter. MUST be a non-empty string and MUST be unique within all dependency parameters. |


here again, field vs parameter.

This is the field that the broker is expecting to look in for the service dependecies? Suppose the broker wanted to accept it in a nested object, I think it might need to be a path to support something like "parameters.dependencies.service"

n3wscott · 2018-04-04T18:05:11Z

spec.md

+| parameter* | string | Name of the parameter. MUST be a non-empty string and MUST be unique within all dependency parameters. |
+| description* | string | A short description of the dependency. MUST be a non-empty string. |
+| optional  | boolean | Whether the dependency is optional or not. Defaults to false. |
+| service_id | string | Service ID of the instance. MUST be a non-empty string. MUST NOT be used in conjunction with the fields `plan_ids` and `service_name`. |


Why not have service_id be service_ids and allow a list?

n3wscott · 2018-04-04T18:33:13Z

spec.md

+
+```
+{
+  "parameters": {


I would recommend pulling out the dependency fields into their own field next to parameters, like:

{ "dependencies" { "service_id": "71ef3933-8520-4f26-b808-f483d23f94a6", "service_name": "mysql", "plan_id": "1b367d58-6f17-4cb3-9ef8-3a69e752b826", "plan_name": "small", }, "parameters": { "database": { "credentials": { "uri": "mysql://mysqluser:pass@mysqlhost:3306/dbname", "username": "mysqluser", "password": "pass", "host": "mysqlhost", "port": 3306, "database": "dbname" } } } }

n3wscott · 2018-04-04T18:37:07Z

spec.md

+
+\* Fields with an asterisk are REQUIRED.
+
+For bindable services, the value MUST contain be the response of a binding request. 


For bindable services, the value MUST contain be the response of a binding request.

I am having a really hard time trying to figure out what this means. The values [in the above table>] must be contained inside the request for binding? What is required about response? I am confused because only requests have "parameters" but this is mixing the request/response demands.

n3wscott · 2018-04-04T18:41:21Z

spec.md

+Instances of non-bindable services can only be provided to the same broker.
+The platform MUST set the instance ID into the parameter value object.
+
+| Field | Type | Description |


Is this a table of allowed additive fields for non-bindable services?

n3wscott · 2018-04-04T18:42:20Z

spec.md

+the structures above. Additionally, the platform MAY add a dependency name,
+set by the user to each object.
+
+| Field | Type | Description |


Is this a table of allowed additive fields for "open deps"?

It took me a very long time to understand this was what this was attempting to say. Perhaps one table with restrictions on the fields?

n3wscott · 2018-04-04T18:44:05Z

spec.md

+```
+{
+  "parameters": {
+    "some_dependencies ": [


If this is suppose to be additive to the OSBAPI, I would recommend not mix instance parameters with broker dependencies. It is really confusing and I suspect this would be difficult to implement cleanly in broker.

n3wscott · 2018-04-04T18:52:46Z

Overall I think this change does not do enough to allow the ecosystem to play nice together. I understand the use-case but I think this implementation is too opinionated about the solution it recommends brokers to implement. I don't see an easy way for broker to broker dependencies, such as the use case where I want to bring my broker that provisions my application, and that application depends on a database of some kind, it would be real nice to be able to say "in my application broker, please tie in a database that speaks SQL".

I think the customizable parameter targets are confusing. And in the very least they need to be paths inside the json object relative to the root of the object.

It would be interesting to use the concept of adheres_to when specify a generic dep.

I think more detail needs to be added around what the platform is expected to do when it provisions something and the catalog can change with more items, or deprovision and items disappear.

I wonder if there is also a chance to add a concept of a service depending on a binding. At the moment we make bindings but we do not get to say who they are for. But a binding could be shared as well so each binding could have n parties using it. I am not sure on that point...

mhrivnak · 2018-04-10T14:16:49Z

I agree with @n3wscott 's summary. It would be helpful to focus more on illustrating the big picture and how the key use cases are fulfilled. Reading this proposal, I found it somewhat difficult to keep track of where things fit in to a high-level workflow, and who-or-what is the actor performing each step.

It may help to focus more on addressing these general questions:

What exactly is the mechanism and algorithm for match-making? There are a lot of details to explore around how a Plan (or other resource maybe) would express what it requires and what it provides. It will help to first describe the data and algorithm without talking about API operations.
What component is expected to execute the match-making algorithm to determine which resource fulfills a requirement? Is it always the Platform?
Once some actor determines which resource fulfills a requirement, what then? What specific actions must that actor take? For example, would the Platform be responsible for creating a binding and passing it (along with additional info about the providing service?) to the service being provisioned?

krancour · 2018-04-19T15:15:48Z

Adding an opinion here that I expressed at the f2f. I believe that solving "adheres to" is a necessary pre-requisite for some of this.

duglin · 2018-05-15T13:44:09Z

Refresh my memory - what's the status of this? Awaiting an updated PR?

Initial draft of service dependencies spec

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n3wscott added the do not merge label Apr 3, 2018

mhrivnak reviewed Apr 3, 2018

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n3wscott reviewed Apr 4, 2018

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duglin added the needs rebase/work label May 15, 2018

fmui closed this Jul 12, 2018

DrackThor mentioned this pull request Mar 7, 2019

Proposal: Add declaration of service instance dependencies #427

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Service dependencies specification #488

Service dependencies specification #488

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n3wscott commented Apr 4, 2018

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krancour commented Apr 19, 2018

duglin commented May 15, 2018 •

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		\* Fields with an asterisk are REQUIRED.

		For bindable services, the value MUST contain be the response of a binding request.

Service dependencies specification #488

Service dependencies specification #488

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fmui commented Apr 3, 2018

cfdreddbot commented Apr 3, 2018

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n3wscott commented Apr 4, 2018

mhrivnak commented Apr 10, 2018

krancour commented Apr 19, 2018

duglin commented May 15, 2018 • edited Loading

duglin commented May 15, 2018 •

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