[pylons-discuss] Re: pyramid_tm - is there an acceptable way to unjoin the transaction and use explicit commits?

[Jonathan Vanasco]

>
> `request.tm.commit()`, `request.tm.abort()` and `request.tm.begin()` 
> instead of `request.dbsession.commit()`. 


Thanks, Michael. This obvious answer is what I'll use.

I am very familiar with Celery and task runners, and have a few app using 
it with Pyramid.

In this particular application, the work/results are all instant - there 
are no potentially long-running subprocesses.  I just need to commit 
multiple times within a view to ensure the database records an action was 
performed.

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Re: [pylons-discuss] pyramid_tm - is there an acceptable way to unjoin the transaction and use explicit commits?

[Michael Merickel]

pyramid_tm does have a configurable activate_hook that you can use to turn
off the TM for certain endpoints. You would need to coordinate that with
something else that managed the transaction. If I were doing it myself I'd
probably configure my activate hook to return true/false based on an custom
attribute on the request like `request.activate_tm`. I'd then set this to
False in a tween mounted over pyramid_tm. The reason I'd do it this way is
because if you're turning off pyramid_tm then you probably still need to do
something to manage the connection - and a tween would be a good spot to do
this.

That being said, I'd ask why you would want to turn it off instead of just
committing multiple times? You just need to use `request.tm.commit()`,
`request.tm.abort()` and `request.tm.begin()` instead of
`request.dbsession.commit()`. Make sure to always call begin after
commit/abort and things should work fine - whether it's a good idea or not
in general (see Mikko's comments) is a separate question.

- Michael

On Thu, Feb 6, 2020 at 7:03 PM Jonathan Vanasco 
wrote:

> one of my apps uses pyramid_tm, but has reached a point where one
> (possibly two) views (out of dozens) need to make explicit commits with the
> SqlAlchemy session.
>
> does anyone know if it's currently possible to handle this?  i have a few
> apps that only integrate pyramid_tm on a small subset of views, but i
> haven't tried to bypass it on a single view in many years.  I'm trying to
> avoid a secondary database connection, because this app can support a
> sqlite database and I've had problems with too many connections and sqlite
> in the past.
>
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> .
>


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Michael

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Re: [pylons-discuss] pyramid_tm - is there an acceptable way to unjoin the transaction and use explicit commits?

[Mikko Ohtamaa]

one of my apps uses pyramid_tm, but has reached a point where one (possibly
> two) views (out of dozens) need to make explicit commits with the
> SqlAlchemy session.
>

Because this does not fit well in the view/request model, I would usually
try to offload these tasks to a worker processes (Celery) where it is much
easier to have a explicit control over the transaction cycle. A request
would only serve as a trigger for the background process. It does not work
for all kind of use cases, though.

-Mikko

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