impl/prod: Make AEContext private.

impl/prod: Make AEContext private.

AEContext is confusing and magical, as is evidenced by #63, exposing
impl/prod's internal structures and a lot of gritty and nuanced details about
how it manages AppEngine SDK Contexts.

Rather than direct users here, let's offer a clean break: users who want
to interact with the Google AppEngine SDK directly must explicitly create
their own Context for this using appengine.(Use|With)Context.
Internally, this is very efficient, as AppEngine retains Contexts bound
to requests in a map.

With this patch the division is clearer: luci/gae will not help you
access the raw AppEngine SDK, period.

BUG=None
TEST=local
  - `goapp test ./impl/prod`

Committed: https://github.com/luci/gae/commit/31b3460980f3e048bb57f214952fb775aa21973f

[dnj, 2016-10-28 17:30:49]

dnj@chromium.org changed reviewers:
+ iannucci@chromium.org

[dnj, 2016-10-28 17:30:50]

PTAL.

I considered, as an alternative, always embedding the AEContext into the
retained Contexts; however, this is problematic b/c it creates the illusion that
the user-supplied Context is being used directly when, in reality, the retained
GAE Context is being used. If you want to see what that looks like, check out:

https://codereview.chromium.org/2460803003

[iannucci, 2016-10-28 18:40:16]

Commented on other CL as well

https://codereview.chromium.org/2460473003/diff/1/impl/prod/context.go
File impl/prod/context.go (right):

https://codereview.chromium.org/2460473003/diff/1/impl/prod/context.go#newcode75
impl/prod/context.go:75: // SDK must derive their own AppEngine Context;
luci/gae will not help you.
I would note that using the raw AppEngine SDK to access any services _covered by
luci/gae_ is dangerous. It's not dangerous to access other services directly.

[dnj, 2016-10-31 16:44:04]

Let's go with this. I've updated the comment.

[iannucci, 2016-11-02 02:06:15]

Yeah, lgtm. I think we should probably also implement the rest of the SDK
services so that the desire to do this is basically gone.

[iannucci, 2016-11-02 02:06:19]

The CQ bit was checked by iannucci@chromium.org

[commit-bot: I haz the power, 2016-11-02 02:06:27]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-02 02:09:45]

Description was changed from

==========
impl/prod: Make AEContext private.

AEContext is confusing and magical, as is evidenced by #63, exposing
impl/prod's internal structures and a lot of gritty and nuanced details about
how it manages AppEngine SDK Contexts.

Rather than direct users here, let's offer a clean break: users who want
to interact with the Google AppEngine SDK directly must explicitly create
their own Context for this using appengine.(Use|With)Context.
Internally, this is very efficient, as AppEngine retains Contexts bound
to requests in a map.

With this patch the division is clearer: luci/gae will not help you
access the raw AppEngine SDK, period.

BUG=None
TEST=local
  - `goapp test ./impl/prod`
==========

to

==========
impl/prod: Make AEContext private.

AEContext is confusing and magical, as is evidenced by #63, exposing
impl/prod's internal structures and a lot of gritty and nuanced details about
how it manages AppEngine SDK Contexts.

Rather than direct users here, let's offer a clean break: users who want
to interact with the Google AppEngine SDK directly must explicitly create
their own Context for this using appengine.(Use|With)Context.
Internally, this is very efficient, as AppEngine retains Contexts bound
to requests in a map.

With this patch the division is clearer: luci/gae will not help you
access the raw AppEngine SDK, period.

BUG=None
TEST=local
  - `goapp test ./impl/prod`

Committed:
https://github.com/luci/gae/commit/31b3460980f3e048bb57f214952fb775aa21973f
==========

[commit-bot: I haz the power, 2016-11-02 02:09:46]

Committed patchset #2 (id:20001) as
https://github.com/luci/gae/commit/31b3460980f3e048bb57f214952fb775aa21973f