As well as TO v2 must support TO API v1 or you risk a nightmare upgrading.
Jonathan G
On 2/14/19, 1:19 PM, "Fieck, Brennan" <brennan_fi...@comcast.com> wrote:
Sure, but TO API v1 would only be implemented by TO v1 and TO API v2 only
implemented by TO v2.
________________________________________
From: Rawlin Peters <rawlin.pet...@gmail.com>
Sent: Thursday, February 14, 2019 12:59 PM
To: dev@trafficcontrol.apache.org
Subject: Re: [EXTERNAL] Re: Traffic Ops API versioning issues
Scripts written against TO API v1 should always work against TO API
v1, no matter if Traffic Ops is v2.2, v3.0, or v4.0. The API version
shouldn't have to match the version of the software that implements
said API.
- Rawlin
On Thu, Feb 14, 2019 at 12:36 PM Fieck, Brennan
<brennan_fi...@comcast.com> wrote:
>
> The idea with regard to breaking changes is that a breaking change in
> the API is seen as a breaking change in TO - so scripts written against
> TO v1 should always work with TO v1. When TO v2 is released, after
> exiting your time machine, you shouldn't expect your v1 scripts to
> work with v2.
> ________________________________________
> From: Rawlin Peters <rawlin.pet...@gmail.com>
> Sent: Thursday, February 14, 2019 10:53 AM
> To: dev@trafficcontrol.apache.org
> Subject: Re: [EXTERNAL] Re: Traffic Ops API versioning issues
>
> There is a lot of stuff to digest here, and I agree that the v1 API is
> desperately in need of a good v2. However, I'm not sure I agree that
> the API should be versioned alongside Traffic Ops. The API version
> should be separate from the Traffic Ops/Traffic Control release
> versions. We should do our best to not break a major API version, so
> in theory a script written against TO API v1 should always work with
> TO API v1. When TO API v2 is introduced, the script written against v1
> would not be guaranteed to work against v2 (although, we should still
> support v1 for some time before deprecating in favor of v2).
>
> - Rawlin
>
> On Thu, Feb 14, 2019 at 8:07 AM Fieck, Brennan
> <brennan_fi...@comcast.com> wrote:
> >
> > I'd take it further, though in my opinion it shouldn't be done until
we're ready to do away with Perl entirely.
> > I've been working on this for a little bit, and I sorta wanted to make
a wiki page for a proposed API v2 design before sending it, but what the heck.
The conversation is here now.
> >
> >
> > I don't like the way our API is versioned. Let me be clear, it _should_
be versioned, and the
> > versions _should_ be semantic, but it is my opinion that the API should
be versioned alongside
> > Traffic Ops rather than at its own pace. I've written essentially an
article on why this should be
> > the case, and it follows:
> >
> > ** TIMING **
> > The first issue I should address is timing - this needn't happen
immediately. For the time being, I
> > think a radical change would be much more harmful than continuing along
our current versioning
> > scheme. This change should be implemented with the advent of what we
currently refer to as "API v2".
> > Presumably, at this time all of the Perl code has been removed and we
are looking to re-tool the API
> > to be more sensible and standards-conforming. It's a time when we'll
already be making big, breaking
> > changes. I personally would love for this to be ATC 4.0, but that may
not be a realistic goal.
> >
> > ** REDUNDANCY **
> > The easiest to see - albiet simultaneously most trivial - issue with
the current API versioning
> > scheme is how every request path must start with '/api/1.x/'. This is
annoying, to be frank;
> > especially when one considers that the current plan for Traffic Ops is
to reduce it entirely to an
> > API, so literally every endpoint will have '/api/' in common. We _know_
the endpoint we are trying
> > to query is an API endpoint because _all_ endpoints are API endpoints.
When we reach "API v2" the
> > '/api/' part of request paths will have lost all value entirely.
> > Even with that gone we are left with '/1.' (or '/2.' as the case may
become) as a common prefix,
> > again annoying although not totally useless in this case. However, the
vast majority of API
> > endpoints see no changes between minor versions, so really '/1.x' just
becomes a static, constant
> > prefix where 'x' is the latest version of the API.
> > In any case, versioning the API alongside Traffic Ops solves this
problem because our Traffic Ops
> > server(s) emit HTTP headers that name the server. Once Perl is gone,
we'll be free to use the HTTP
> > `Server:` header to name the server e.g. `Server: Traffic Ops/3.2.1`.
At this point, we could
> > either implement an `OPTIONS` method request at the server's root that
would just return some
> > headers - including `Server:` or just let people to a `GET` (or better
yet `HEAD`) request to
> > `/ping` and pull the server version out of the headers. The client then
has all the information it
> > needs to communicate effectively with the server. The alternative to
this within our current
> > versioning schema is to implement an unversioned API endpoint such that
we have a hundred `/api/1.x`
> > endpoints and one that has some other - or possibly no - prefix, or
have a versioned API version API
> > endpoint, which is confusing even just to say.
> >
> > ** TRAFFIC OPS _IS_ THE API **
> > As mentioned previously, the endgame of our transition from Perl to Go
is that Traffic Portal is the
> > only UI for ATC - and in fact that's already somewhat true. That leaves
Traffic Ops as a database
> > and a REST API for interacting with said database. In fact, the
database is often referred to as its
> > own service: "ToDb", "Traffic Ops DB" etc. That means that we have the
single most important Traffic
> > Control component split in two - half of its functionality is versioned
sanely with Traffic Control
> > while the other half is versioned separately from anything else in the
world. That's crazy, because
> > if you have a program that only does two things, then surely a breaking
change to one of those
> > things means increasing its major version? If that's the case, then why
are we not versioning the
> > API alongside Traffic Ops?
> > It may be argued (incorrectly, in my opinion) that Traffic Ops does
more than serve an API to
> > interact with a database. It generates configuration files and system
images, it combines data and
> > does heavy processing on it. But really those things shouldn't be taken
into account in a versioning
> > scheme except insofar as they affect the experience of some user,
administrator, or application
> > interfacing with Traffic Ops. If the API responses don't change in form
or content, and if the
> > process of setting up or maintaining the application haven't changed,
then any code changes you've
> > made are a patch, not a version change. Traffic Ops does big things,
but at the end of the day it
> > all just boils down to API inputs and outputs as far as anything and
anyone else is concerned.
> >
> > ** CONFUSION **
> > We currently live in a world where I can run a script using the Traffic
Ops API that works perfectly
> > fine against Traffic Ops version 3.2.1, but then if I again test it
against version 3.2.1 at some
> > point in the future it breaks because breaking changes were made in the
API. It's easy to say, "oh,
> > that just means that when we make breaking API changes we should
increment the version
> > appropriately," but realize that this _is versioning the API alongside
Traffic Ops_. If we're not
> > doing that, we're saying there is unpredictability with the behavior of
our system within releases,
> > and if we _are_ doing that then the only difference between the API
version and the Traffic Ops
> > version is that the API version is confusingly behind by about 2 major
revisions. It should just be
> > the same for simplicity's sake.
> >
> > ** THE API "PROMISE" **
> > The single most common argument I hear in favor of our current API
versioning scheme is "well we've
> > said an API version 1.x behaves in this way, and so we must uphold that
promise to the user base".
> > Not only do we routinely break that promise already,
> > (e.g. PR #3110 [https://github.com/apache/trafficcontrol/pull/3110])
but I'm certainly not
> > suggesting that we don't uphold this promise. Yes, this does mean that
making breaking API changes
> > in TO would require a new major release and adding features/fields to
the API would require a new
> > minor release. I don't see that as a big deal, especially if
implemented at the time I'm suggesting
> > when we'd be re-designing the API - and it does sorely need to be
redesigned.
> >
> > * The API Needs to be Redesigned *
> > I'm going to go down this rabbit hole for a second, if you're already
convinced the TO API needs a
> > re-design then feel free to skip this section. I'm not going to touch
on any problems caused in the
> > API as currently implemented by the use of a standalone API version -
that's what the entire article
> > is for.
> > Currently, our API currently has three huge problems:
> >
> > 1. Rampant oversaturation of endpoints
> > We have a systemic issue of re-implementing behaviour in
multiple endpoints. This is due in part
> > to a lack of good documentation - so developers aren't aware of
the endpoints available to them
> > - and partly because of the "Mojolicious Mindset" that plagues
our oldest endpoints. The
> > "Mojolicious Mindset" refers to the use of URL path fragments
as request parameters, e.g.
> > '/users/{{ID}}' instead of/in addition to '/users?id={{ID}}'.
From the perspective of someone
> > who is just writing the back-end for these endpoints, there's
no clear advantage to one over the
> > other except that the former seems to more clearly reflect the
intent of requesting a specific
> > object whereas the latter could be seen as more of a "filter"
on a larger collection. That's not
> > incorrect, necessarily, but the two are totally separate
request paths, so having '/users' and
> > '/users/{{ID}}' means documenting two endpoints instead of one,
and it means two lines in the
> > route definitions, and it means two seperate handlers instead
of one (albiet a more complex
> > one).
> > Consider also that we have all of the following endpoints for
manipulating Cache Groups:
> >
> > * /api/1.x/cachegroup/{{parameter ID}}/parameter
> > * /api/1.x/cachegroup_fallbacks
> > * /api/1.x/cachegroupparameters
> > * /api/1.x/cachegroupparameters/{{ID}}/{{parameter ID}}
> > * /api/1.x/cachegroups
> > * /api/1.x/cachegroups/{{ID}}
> > * /api/1.x/cachegroups/{{ID}}/deliveryservices
> > * /api/1.x/cachegroups/{{ID}}/parameters
> > * /api/1.x/cachegroups/{{ID}}/queue_updates
> > * /api/1.x/cachegroups/{{ID}}/unassigned_parameters
> > * /api/1.x/cachegroups/{{parameter ID}}/parameter_available
> > * /api/1.x/cachegroups_trimmed
> >
> > These could all be collapsed neatly into one or two endpoints, but
were instead implemented
> > separately for whatever reason(s)
> > (see Issue #2934
[https://github.com/apache/trafficcontrol/issues/2934] for details).
> >
> > 2. Improper/Non-existent standards conformity
> > We have requests that should be read-only that make server-side
state changes (Issue #3054
> > [https://github.com/apache/trafficcontrol/issues/3054]), we
have endpoints returning success
> > responses on failure (Issue #3003
[https://github.com/apache/trafficcontrol/issues/3003]) and
> > our "CRUDER" has failed us. `PUT` should be used to _create_
objects (or possibly update them by
> > creating an alternative representation with the same
identifiying information) but is instead
> > used as the primary "edit this" method. `POST` is for
processing entities in a data payload, but
> > is instead used for object creation. `PATCH` languishes,
totally unimplemented. These problems
> > are systemic and stem partially from the "Mojolicious Mindset"
whereby new functionality is
> > introduced into the API by first considering what request
method is appropriate and then
> > deciding on a request path that names the operation being done.
Request methods are meant to be
> > the different ways in which a client interacts with a resource
on the server, and thus the
> > resources themselves should be considered primary. The "CRUDER"
hampers this mindset, because it
> > makes treating payloads and query parameters generic and isn't
receptive to injection of new
> > behaviour.
> > The "CRUDER" is a great innovation, to be sure, as it saves us
quite a bit of time and prevents
> > duplicating code, but the problem it solves is an emergent
property of of API problem #1 above.
> > With fewer endpoints we'd have much more specific handling, and
the need for and advantages of
> > the "CRUDER" will vanish.
> >
> > 3. Needing multiple queries to obtain a single piece of information
> > This issue is pretty deeply rooted, and is related to the way
our database is structured. But
> > that's part of the problem - an API needn't replicate the
database, and is therefore free from
> > some of the constraints that bind a database.
> > The way things are now, in order to e.g. create a server
definition I must make several
> > preliminary requests to determine the integral, unique,
non-deterministic identifiers of other
> > objects. I think we all agree that ideally these integral IDs
would have no part in the output
> > of the API, and many people I've spoken to would support wiping
them from the database entirely
> > given enough time and manpower.
> >
> > ________________________________________
> > From: Robert Butts <r...@apache.org>
> > Sent: Wednesday, February 13, 2019 6:11 PM
> > To: dev@trafficcontrol.apache.org
> > Subject: Re: [EXTERNAL] Re: Traffic Ops API versioning issues
> >
> > >It doesn't seem like the idea of full TO API SemVer was ever fully
> > discussed and voted on
> >
> > >Since it seems like we never truly committed to SemVer with minor
versions
> > for the TO API
> >
> > There was consensus:
> >
https://lists.apache.org/thread.html/8f8a850c68424021a0fe06967894383a24e463f1b0cee4d652d04590@%3Cdev.trafficcontrol.apache.org%3E
> >
https://lists.apache.org/thread.html/1a42a2192a81fc4d76639ccd10761b6b73c31345a63715bb8aa86e4e@%3Cdev.trafficcontrol.apache.org%3E
> >
> > We didn't do an official [VOTE], but we rarely do that as a project,
unless
> > there's difficulty reaching unofficial consensus. That said, there's
> > nothing stopping another discussion or vote, if we want to change
things.
> >
> > >as long as we set the expectations for the user
> >
> > That's precisely my point. We can always say "we set the expectations,
it's
> > the user's fault for misreading, or misunderstanding, or not noticing a
> > changelog." It's not about fault, it's about providing a better user
> > experience.
> >
> > >that support has to be baked into traffic_ops_golang such that it's
easy
> > and maintainable to support tons of minor versions. If we keep heading
down
> > our current path we are going to be left with a giant mess.
> >
> > I don't think anyone disagrees. Traffic Ops versioning has had
considerable
> > technical debt for some time now. We just haven't been willing to spend
the
> > time to fix it. I agree, that needs to change.
> >
> > I'd also like to note, there's another option: code generation. We can
keep
> > the structs and handlers largely the same, and generate the "duplicate"
> > code when a new minor version is added. There's a strong argument that
this
> > is the "idomatic" way to solve this problem, for the Go language. I
> > personally feel Reflection is better here. But, I wanted everyone to be
> > aware that's an option, if the consensus is that it's the best option.
In a
> > nutshell, we could generate code with a script (with a spectrum of
> > precision and complexity, from `cp && sed` to parsing the AST), and
> > `routes.go` would have a `//go:generate` header. For examples, see:
> >
> > https://blog.golang.org/generate
> > https://godoc.org/golang.org/x/tools/cmd/stringer
> >
> > I did some prototyping of that approach, if anyone is interested, just
let
> > me know and I can provide examples of what that would look like.
> >
> >
> > On Wed, Feb 13, 2019 at 5:09 PM Rawlin Peters <rawlin.pet...@gmail.com>
> > wrote:
> >
> > > On Wed, Feb 13, 2019 at 1:20 PM Gray, Jonathan
> > > <jonathan_g...@comcast.com> wrote:
> > > >
> > > > I'm +1 on keeping full API SemVer.
> > >
> > > > On 2/13/19, 12:16 PM, "Robert Butts" <r...@apache.org> wrote:
> > > >
> > > > We would be abandoning Semantic Versioning.
> > >
> > > This is why I wanted to open this up for broader discussion within the
> > > community. It doesn't seem like the idea of full TO API SemVer was
> > > ever fully discussed and voted on (at least not to my knowledge),
> > > which is why I haven't been abiding by it myself or enforcing it upon
> > > other TO API devs either. If we're going to truly commit to SemVer
> > > with minor versions for TO API then we should fully understand the
> > > cost vs utility of doing so. Also, SemVer doesn't have to be an "all
> > > or nothing" thing, as we currently choose to ignore the "patch"
> > > version for the TO API. We could also choose to ignore the minor
> > > version and just focus on the most important aspect of SemVer which is
> > > not introducing backwards-incompatible changes in the same major
> > > version.
> > >
> > > Since it seems like we never truly committed to SemVer with minor
> > > versions for the TO API, traffic_ops_golang wasn't designed to easily
> > > support minor versions. So if we're going to truly commit to SemVer
> > > with minor versions for TO API, then that support has to be baked into
> > > traffic_ops_golang such that it's easy and maintainable to support
> > > tons of minor versions. If we keep heading down our current path we
> > > are going to be left with a giant mess.
> > >
> > > The only way I can get behind supporting the "minor version promise"
> > > is if we have a way to basically just tag fields as introduced in a
> > > specific API version, with just a single struct per resource and a
> > > single handler per major version of an endpoint. We should only
> > > require a single implementation of an endpoint per major version. If a
> > > custom JSON parser allows us to do that, then that's great. Without
> > > that, I don't think supporting the "minor version promise" is even a
> > > viable option.
> > >
> > > A lot of those scenarios around user confusion due to supporting just
> > > a major version are not really an issue as long as we set the
> > > expectations for the user. I.e.:
> > > - clients should request v1
> > > - as the v1 API is enhanced in a backwards-compatible manner, clients
> > > will begin to see new fields in the server responses
> > > - if a client wants to modify a resource, they will typically do a GET
> > > on the resource, modify the resource, then do a PUT back to the
> > > server.
> > > - in the GET response, if the client sees new fields, they can expect
> > > to modify those fields and see it reflected on the server.
> > > - if the client does NOT see new fields, then they cannot add fields
> > > and expect to see that reflected on the server
> > > - null values in optional fields will be interpreted by the server as
> > > whatever the default for that optional field is. So if the default for
> > > new optional field "foo" is 5, then a client sending `"foo": null`
> > > will be interpreted by the server as `"foo": 5`, and `"foo": null`
> > > should never have a different meaning than `"foo": 5` on the server.
> > >
> > > The advantage of just supporting the "major version promise":
> > > - jives better with Go's lack of metaprogramming
> > > - no custom JSON parser in Go required
> > > - less general overhead in development
> > > - only have to worry about breaking changes
> > > - no worrying about which fields belong to which minor versions
> > > - no extra API testing to make sure fields introduced in API v1.N
> > > aren't returned to v1.N-1 clients
> > > - don't have to update every single client in the repo with the new
> > > minor version every time a minor version is incremented (since clients
> > > would just specify the major version)
> > >
> > > So, as a community, we need to weigh these options and decide whether
> > > or not we want to take the "major version only" route or the "major
> > > plus minor version" route. Personally, I prefer the "major version
> > > only" route because it means less code, less overhead, less
> > > coordination, and less things to potentially go wrong. However, if a
> > > relatively small custom JSON parser is all we really need to
> > > reasonably support the "minor version promise", then I can't say I'm
> > > completely against that route either (just that I wouldn't prefer it).
> > >
> > > - Rawlin
> > >
