A single SchemaCache instance is maintained by the connection pool, and made available via a schema_cache method on each connection. When the SchemaCache instance is fetched from the pool, its internal connection reference is updated to equal the requesting connection. However, since there is only one instance of SchemaCache, this internal connection reference is updated everywhere, and can ultimately result in multiple threads accessing the same database connection. In Discourse, this could result in Sidekiq jobs getting 'stuck' in database connections.
This patch modifies SchemaCache so that it caches the internal connection on a per-thread basis
Co-authored-by: Sam Saffron <sam.saffron@gmail.com>
Co-authored-by: Matt Palmer <mpalmer@hezmatt.org>
Previously we had many places in the app that called `hostname` to get
hostname of a server. This commit replaces the pattern in 2 ways
1. We cache the result in `Discourse.os_hostname` so it is only ever called once
2. We prefer to use Socket.gethostname which avoids making a shell command
This improves performance as we are not spawning hostname processes throughout
the app lifetime
Doing .pluck(:column).first is a very common pattern in Discourse and in
most cases, a limit cause isn't being added. Instead of adding a limit
clause to all these callsites, this commit adds two new methods to
ActiveRecord::Relation:
pluck_first, equivalent to limit(1).pluck(*columns).first
and pluck_first! which, like other finder methods, raises an exception
when no record is found
This reverts commit ab74a50d85.
We really want to upgrade redis, but discovered some edge cases
around failover we need to test.
Holding off on the upgrade till a bit more testing happens
I introduced DemonBase because I had got some conflict between `demon/base.rb` and `jobs/base.rb`, however, to not rename base class, it is possible to use regex on absolute path in Zeitwerk custom inflector.
Zeitwerk simplifies working with dependencies in dev and makes it easier reloading class chains.
We no longer need to use Rails "require_dependency" anywhere and instead can just use standard
Ruby patterns to require files.
This is a far reaching change and we expect some followups here.
This is a temporary workaround for the issue in https://github.com/rails/rails/pull/36949
Discussing a proper fix in Rails with the Rails team.
Prior to this fix we were spinning up a thread every time we closed a connection
to the db.
* Adjustments to pass specs on Rails 6.0.0
* Use classic autoloader instead of Zeitwerk
* Update Rails 6.0.0 deprecated methods
* Rails 6.0.0 not allowing column with integer name
* Drop freedom_patches/rails6.rb
* Default value for trigger_transactional_callbacks? is true
* Bump rspec-rails version to 4.0.0.beta2
Sometimes we would like to create a base image without any DB access, this
assists in creating custom base images with custom plugins that already
includes `public/assets`
Following this change set you can run:
```
SPROCKETS_CONCURRENT=1 DONT_PRECOMPILE_CSS=1 SKIP_DB_AND_REDIS=1 RAILS_ENV=production bin/rake assets:precompile
```
Then it is straight forward to create a base image without needing a DB or
Redis.
Previously as soon as any override was defined we would regress to the slow
path for locale lookups. Additionally if `raise: true` was specified which
rails likes to add in views we would bypass the cache
The new design manages to use the fast path for many more cases
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
Minor fixes to add Rails 6 support to Discourse, we now will boot
with RAILS_MASTER=1, all specs pass
Only one tiny deprecation left
Largest change was the way ActiveModel:Errors changed interface a
bit but there is a simple backwards compat way of working it
This removes a monkey patch we no longer need since our containers require
2.5.2 or up for all Discourse installs.
If you are looking to deploy on 2.5.1 which is highly not recommended you
will need to figure out how to apply this diff.
New method deprecator will ensure one log message an hour happens
for all deprecated method calls per call site
Also removes unused monkey patches to ActiveRecord::Base
The Rails 5.2 connection reaper appears to be leaking threads
this is a quick fix to stop it, though we need to make sure we
never leak connection pools as well.
