Rails Receives Repetitive Requests on One Request - ruby-on-rails

Question

My route is as follows:
Rails.application.routes.draw do
get 'courses' => 'application#index'
get 'check_db' => 'application#check_db'
root 'application#index'
end
And my application#check_db is
def check_db
p "test"
redirect_to root_path
end
When I visit /check_db on my browswer (tried both in Chrome and Safari), if working properly, it should GET "/check_db" and then GET "/". But actually, the log shows that there are four requests, with the above pattern repeated twice (i.e. GET "/check_db", GET "/", GET "/check_db", GET "/"). There is absolutely no code in my application#index that does any other redirection. So why is this?
The situation described above happen most of the times. However, occasionally, it works as expected. I did not change the code in the interim.
If it is in interest, the entire log is pasted below:
Started GET "/check_db" for ::1 at 2017-01-04 17:05:06 -0800
Processing by ApplicationController#check_db as HTML
"test"
Redirected to http://localhost:3000/
Completed 302 Found in 1ms
Started GET "/" for ::1 at 2017-01-04 17:05:06 -0800
Processing by ApplicationController#index as HTML
Rendering application/index.html.erb within layouts/application
[MongoDB query log]
Rendered application/index.html.erb within layouts/application (3.4ms)
Completed 200 OK in 18ms (Views: 16.4ms)
Started GET "/check_db" for ::1 at 2017-01-04 17:05:07 -0800
Processing by ApplicationController#check_db as HTML
"test"
Redirected to http://localhost:3000/
Completed 302 Found in 8ms
Started GET "/" for ::1 at 2017-01-04 17:05:07 -0800
Processing by ApplicationController#index as HTML
Rendering application/index.html.erb within layouts/application
[MongoDB query log]
Rendered application/index.html.erb within layouts/application (4.1ms)
Completed 200 OK in 17ms (Views: 15.0ms)