On Tue, Mar 2, 2021 at 10:24 AM armin <[email protected]> wrote:

> Hello!
>
> I have a hanami 1.3 app, but the issue should be unrelated to hanami. I
> want to connect to a second db with plain Sequel-gem. Therefore I define
> the connection in hanami's `config/environment.rb`, which is required in
> `config/puma.rb`:
>
> ```ruby
> # config/environment.rb
> # ...
> DWH = Sequel.connect(ENV['DWH'], :loggers => [Logger.new($stdout)])
> #...
> ```
> In production I have a puma-config like that:
>
> ```ruby
> # config/puma.rb
> require_relative './environment'
> workers 5
>
> threads_count = 1
> threads threads_count, threads_count
>
> daemonize true
>
> preload_app!
>
> rackup      DefaultRackup
> port        2300
> environment 'production'
>
> before_fork do
>   DWH.disconnect
> end
>
> on_worker_boot do
>   Hanami.boot
> end
> ```
> I used the `before_fork` hook to disconnect the db (
> http://sequel.jeremyevans.net/rdoc/files/doc/fork_safety_rdoc.html). But
> after some time I get errors like that:
>
> ```txt
> Sequel::DatabaseDisconnectError: PG::UnableToSend: SSL SYSCALL error: EOF
> detected
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:166:in
> `async_exec'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:166:in
> `block in execute_query'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/database/logging.rb:49:in
> `log_connection_yield'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:166:in
> `execute_query'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:153:in
> `block in execute'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:129:in
> `check_disconnect_errors'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:153:in
> `execute'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:515:in
> `_execute'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:327:in
> `block (2 levels) in execute'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:537:in
> `check_database_errors'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:327:in
> `block in execute'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/database/connecting.rb:301:in
> `block in synchronize'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/connection_pool/threaded.rb:107:in
> `hold'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/database/connecting.rb:301:in
> `synchronize'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:327:in
> `execute'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/dataset/actions.rb:1135:in
> `execute'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/adapters/postgres.rb:680:in
> `fetch_rows'
>
>  
> /home/usr/vendor/bundle/ruby/2.6.0/gems/sequel-4.49.0/lib/sequel/dataset/actions.rb:155:in
> `each'
>   /home/usr/app/lib/repositories/dwh_repository.rb:39:in `to_a'
> ```
> Maybe somebody can help and has a hint or an idea, what's the reason for
> the SequelDatabaseDisconnectError.
>

The application lost connection to the database.  When this happens, a
DatabaseDisconnectError is raised and Sequel removes the connection from
the connection pool.  New connection will be created as needed up to the
maximum pool size.  This is expected behavior.

The best course of action is to fix your setup so your database does not
drop application connections.  However, if that is not possible, you can
try the connection_validator extension, which can check connections before
use and automatically get a new connection if an existing connection is
bad, without the user seeing an error.

Thanks,
Jeremy

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