The server log is simply the output on your screen that appears after
your run rails server.
Each time you access a URL in your application, you will see an audit trail appear in the server log. Here's a typical example:
Started GET "/stations" for 127.0.0.1 at 2018-02-01 12:54:42 -0600
Processing by StationsController#index as HTML
Rendering stations/index.html.erb within layouts/application
Station Load (0.1ms) SELECT "stations".* FROM "stations"
Rendered stations/index.html.erb within layouts/application (1.0ms)
Completed 200 OK in 9ms (Views: 6.8ms | ActiveRecord: 0.1ms)
It's important to know how to scan this kind of information.
Started GET "/stations" for 127.0.0.1 at 2018-02-01 12:54:42 -0600
This shows that the browser is trying to use the URL path /stations, and this
is the beginning of the request-response cycle. You can also the IP address
of the machine making the request (127.0.0.1) and the date and time
of the request.
Processing by StationsController#index as HTML
This means that you routes.rb file supports the URL path, and Rails was
able to start processing the request.
Lines like this:
Rendering stations/index.html.erb within layouts/application
and
Rendered stations/index.html.erb within layouts/application (1.0ms)
mean that Rails decided to use the app/views/stations.html.erb
file in order to generate an HTML response. Rails will first
evaluate any Ruby that's embedded in the file, until only plain
HTML remains to be sent.
This line always appears last in the cycle:
Completed 200 OK in 9ms (Views: 6.8ms | ActiveRecord: 0.1ms)
The code 200 means that the request was handled successfully.