Am 03.03.2021 00:35, schrieb Jeremy Evans:
On Tue, Mar 2, 2021 at 12:30 PM Armin Wurzinger <[email protected]>
wrote:
Am 02.03.2021 20:35, schrieb Jeremy Evans:
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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[1].
Which setup do you mean? What can be the reason, that my DB drops the
connection? Timeout?
Fix whatever is causing the connection to drop. Could be a database
setting, firewall setting, etc.. In general, if you can avoid the
disconnects happening in the first place, then you don't need to worry
about how to handle them. It's only if there is nothing you can do and
disconnects will happen anyway that you need something like the
connection_validator extension.
Thanks,
Jeremy
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[2].
Alright, now it seems clearer to me. The other app (with Sequel 5),
where no errors occur, runs on the same server as the DB (maybe that's
the reason, why there's another behavior). The current app runs on a
different server, but in same network. I don't think, PostgreSql-DB
drops the connections (I see them in pg_stat_activity), I think it's a
tcp timeout after some time, but I'm not sure.
PostgreSql-Tcp-Settings
tcp_keepalives_idle: 7200
tcp_keepalives_count: 9
tcp_keepalives_interval: 75
Thank you!
Best regards
Armin
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