Rails core - Jul 2012 - Database connection parameters are tied to the filesystem

HI Guys,

I recently tried VERY hard to override the database configuration bassed on 
ENV vars or actual API calls. This task is almost next to impossible. 

I know that the database.yml file is parsed as ERB but that is sane for 
simple ENV replacement if you want to actually change which database 
adaptor it is (requires extra config/params) it becomes messy. 

I found https://github.com/rails/rails/issues/5297  which explains the 
issue/solution far better then I could. 

Active record supports this natively, I can''t see why rails would force
the
requirement of a database.yml and for it to have a "production"
section.
see http://apidock.com/rails/ActiveRecord/Base/establish_connection/class 
URL section.

Regards

David

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On Tue, Jul 17, 2012 at 9:59 AM, David Rubin <davidrub@gmail.com>
wrote:
> HI Guys,
>
> I recently tried VERY hard to override the database configuration bassed on
> ENV vars or actual API calls. This task is almost next to impossible.
>
> I know that the database.yml file is parsed as ERB but that is sane for
> simple ENV replacement if you want to actually change which database
adaptor
> it is (requires extra config/params) it becomes messy.
>
> I found https://github.com/rails/rails/issues/5297  which explains the
> issue/solution far better then I could.
>
> Active record supports this natively, I can''t see why rails would
force the
> requirement of a database.yml and for it to have a "production"
section. see
> http://apidock.com/rails/ActiveRecord/Base/establish_connection/class URL
> section.
As I mentioned on the ticket, I would rather have ENV["DATABASE_URL"]
supported as well, but I can''t see how it''s "VERY hard to
override".
See https://github.com/rails/rails/issues/5297#issuecomment-7037942

I''ve been using variations of that for a long time, and it works pretty
well.

Cheers,
-foca
> Regards
>
> David
>
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On Tue, Jul 17, 2012 at 12:17:26PM -0300, Nicolás Sanguinetti
wrote:
> On Tue, Jul 17, 2012 at 9:59 AM, David Rubin <davidrub@gmail.com>
wrote:
> > HI Guys,
> >
> > I recently tried VERY hard to override the database configuration
bassed on
> > ENV vars or actual API calls. This task is almost next to impossible.
> >
> > I know that the database.yml file is parsed as ERB but that is sane
for
> > simple ENV replacement if you want to actually change which database
adaptor
> > it is (requires extra config/params) it becomes messy.
> >
> > I found https://github.com/rails/rails/issues/5297  which explains the
> > issue/solution far better then I could.
> >
> > Active record supports this natively, I can''t see why rails
would force the
> > requirement of a database.yml and for it to have a
"production" section. see
> > http://apidock.com/rails/ActiveRecord/Base/establish_connection/class
URL
> > section.
> 
> As I mentioned on the ticket, I would rather have
ENV["DATABASE_URL"]
> supported as well, but I can''t see how it''s "VERY
hard to override".
> See https://github.com/rails/rails/issues/5297#issuecomment-7037942
> 
> I''ve been using variations of that for a long time, and it works
pretty well.
3.2+ should have support for a DATABASE_URL environment variable:

 
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_handling.rb#L39

Which you should be able to use like this:

  $ DATABASE_URL=''sqlite3:///db/development.sqlite3'' rake
do:whatever

But that doesn''t help the problem in #5297.  The problem in #5297 is
that Heroku calculates it''s own parameters to pass in for the URL.
AFAIK, there is no way to augment the connection parameters that Heroku
sends.  But this seems like an issue with Heroku rather than Rails.

If you find entry points where the environment variable *isn''t* used,
then we should consider it a bug.  For example, I just discovered that
`rake db:schema:dump` will not use the environment variable:

 
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/railties/databases.rake#L229

So someone should send a patch for that. :-)

-- 
Aaron Patterson
http://tenderlovemaking.com/

On Tue, Jul 17, 2012 at 2:27 PM, Aaron Patterson
<tenderlove@ruby-lang.org> wrote:
> If you find entry points where the environment variable *isn''t*
used,
> then we should consider it a bug.  For example, I just discovered that
> `rake db:schema:dump` will not use the environment variable:
>  
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/railties/databases.rake#L229
>
> So someone should send a patch for that. :-)
Is it simple as:

-        ActiveRecord::Base.establish_connection(Rails.env)
+        ActiveRecord::Base.establish_connection(ENV["DATABASE_URL"]
|| Rails.env)

wherever I see it not being used? Also inside namespace :test? Are
there tests for rake tasks?

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On Sun, Jul 22, 2012 at 12:52:26PM -0400, TuteC wrote:
> On Tue, Jul 17, 2012 at 2:27 PM, Aaron Patterson
> <tenderlove@ruby-lang.org> wrote:
> > If you find entry points where the environment variable
*isn''t* used,
> > then we should consider it a bug.  For example, I just discovered that
> > `rake db:schema:dump` will not use the environment variable:
> >  
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/railties/databases.rake#L229
> >
> > So someone should send a patch for that. :-)
> 
> Is it simple as:
> 
> -        ActiveRecord::Base.establish_connection(Rails.env)
> +       
ActiveRecord::Base.establish_connection(ENV["DATABASE_URL"]
> || Rails.env)
> 
> wherever I see it not being used?
Yes, but I think it would be better if we change the definition of
`establish_connection` in connection_handling.rb.  Like this:

diff --git a/activerecord/lib/active_record/connection_handling.rb
b/activerecord/lib/active_record/connection_handling.rb
index bda41df..ce1f84f 100644
--- a/activerecord/lib/active_record/connection_handling.rb
+++ b/activerecord/lib/active_record/connection_handling.rb
@@ -36,7 +36,7 @@ module ActiveRecord
     #
     # The exceptions AdapterNotSpecified, AdapterNotFound and ArgumentError
     # may be returned on an error.
-    def establish_connection(spec = ENV["DATABASE_URL"])
+    def establish_connection(spec = ENV["DATABASE_URL"] || Rails.env)
       resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new
spec, configurations
       spec = resolver.spec
 
Then we should just call `establish_connection` and it will
automatically choose the right thing.  (Note that this diff may break
stuff, I haven''t run the tests to find out ;-) )
> Also inside namespace :test?
Yes.
> Are there tests for rake tasks?
There should be tests in Railties.

-- 
Aaron Patterson
http://tenderlovemaking.com/

I have submitted a pull request to fix support for DATABASE_URL environment 
variable:

https://github.com/rails/rails/pull/7521

It includes fix for rake db:schema:dump and other rake db tasks, plus new 
tests to verify correct behavior whether DATABASE_URL environment variable 
is set or not.

All tests were re-run after fix and completed successfully.

Any feedback for changes are welcomed.

Best,
Grace

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I have submitted a pull request to fix DATABASE_URL support:

https://github.com/rails/rails/pull/7521 

The fix addresses rake db:schema:dump as well as other rake db tasks, and 
includes new tests to validate behavior for both with and without 
DATABASE_URL environment variable set.

All tests have been run after the fix was applied and completed 
successfully.

Any feedback welcomed.

Best,
Grace

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