Log SQL queries to console
ActiveRecord::Base.logger = Logger.new(STDOUT)
Tail test log file when running test
In a separate terminal window:
tail -f log/test.log
List object methods
User.methods - ActiveRecord::Base.methods
Warnings
Boot app with $VERBOSE = true in config/application.rb or somewhere that executes
Vendor everything
When vendoring/caching all gems, while developing on OS X but deploying with Alpine Linux, we need to download and cache gems for all platforms. This grabs the Linux version of the Nokogiri gem.
bundle package --all-platforms
Use the Ruby database schema format
Rails configures dumping the Active Record database schema in the development, test and CI environments, out of the box using a Ruby format.
The nice thing about that layer of indirection is that it is more resilient to small differences in different database versions.
Typically what happens for Rails applications at the point a database function, trigger, or some other native item is introduced to the app, is that the .sql format is adopted.
That works but can introduce breakages due to slighy differences in PG versions between multiple environments, which can be quite irritating.
A better solution is to use the fx gem. With fx, native database functions can be dumped into the Ruby schema format. Yay!
Remove unused indexes
In a Rails migration, check for the existence of the index like: index_exists?(:table_name, :column_name) before writing it. Indexes may have different generated names in different environments.
Use Strong Migrations
Follow the tips in strong_migrations. Create your own custom checks. Explain your rationale when using safety_assured.
Bundler platforms
If developing on OS X, deploying on Linux, and vendoring gems, the Darwin pre-built gem will be installed. Add the Linx platform:
bundle lock --add-platform x86_64-linux
And then bundle package --all-platforms and confirm the Linux version has been added to vendor/cache.
Prefer simple dependency specifications
Sometimes there is a minimum version required that has a security fix, a team member recently introduced this:
gem 'addressable', '~> 2.8', '>= 2.8.0'
This makes bundle update addressable easy in the future, grabbing any new patch version of the 2.8 minor version, while still calling out that 2.8.0 should be the minimum patch version that has a security fix.
In general I prefer to avoid specifying versions entirely in the Gemfile and rely on the versions in Gemfile.lock, which has specific versions for direct and indirect dependencies.
Connection Pool Stats
ActiveRecord::Base.connection_pool.stat
# => {:size=>32, :connections=>0, :busy=>0, :dead=>0, :idle=>0, :waiting=>0, :checkout_timeout=>4.0}
Rspec Tips
- Run specific spec: use line number on end like
rspec spec/foo_spec.rb:123to run line 123
Source location
This is more of a Ruby tip but you can get a method reference and use source location. For example with an instance of foo:
Foo.new the method method can be called with a method name like bar, e.g. Foo.new.method(:bar).source_location and calling source_location will show the line number of the caller.
Statement timeout
Set a statement_timeout in config/database.yml to set an upper bound on how long a query can run. We use 5 seconds for our app servers. Hashrocket: Rails/PG Statement Timeout
For queries that are ok to run longer, or migrations, a higher value is appropriate. We use Strong Migrations which raises the statement timeout.
Checkout timeout
Set a checkout_timeout to set how long to wait to check out a connection from the connection pool. The default is 5 seconds but we set it to 4 seconds. Rails Conection Pool Docs