Timeout with ActiveRecord（ActiveRecord::ConnectionTimeoutError ） - ruby

Question

While creating an application using ActiveRecord with sinatra, I encountered such an error.
    
ActiveRecord::ConnectionTimeoutError at / could not obtain a database
connection within 5.000 seconds (waited 5.005 seconds)
What I was about to do was to "get a profile image from Twitter API, save it in a database, and embed it in index.erb". I stopped here.
The code is below.
main.rb
require "sinatra"
require "sinatra/reloader"
require "twitter"
require "active_record"
ActiveRecord::Base.establish_connection(
adapter: "sqlite3",
database: "./image.db"
)
class Src < ActiveRecord::Base
end
def get_profile_image
#srcs = Src.order("id desc").all
end
def add_profile_image(twitter_id)
client = Twitter::REST::Client.new(
consumer_key: "[CONSUMER_KEY]",
consumer_secret: "[CONSUMER_SECRET]",
access_token: "[ACCESS_TOMEN]",
access_token_secret: "[ACCESS_TOKEN_SECRET]"
)
user = client.user(twitter_id)
url = user.profile_image_url
src = Src.new(account: twitter_id, url: url)
src.save
end
def delete_img(twitter_id)
Src.find_by(account: twitter_id).delete
end
get "/" do
get_profile_image
erb :index
end
post "/" do
add_profile_image(params[:id])
get_profile_image
erb :index
end
get "/delete" do
delete_img(params[:id])
get_profile_image
erb :index
end
index.erb
<form method="post" action="/">
<input type="text" name="id">
<input type="submit" value="enter">
</form>
<form method="get" action="/delete">
<input type="text" name="id">
<input type="submit" value="delete">
</form>
<% #srcs.each do |src| %>
<div id="images-space" style="float: left;" class="imgs">
<img data-id="<%= src.id %>" src="<%= src.url %>">
</div>
<% end %>
DB table name is "srcs" and column is
id integer primary key
account text
url text
This kind of error is the first time for me, but where is the problem?

Answer 1

Decouple the connection to your database from your code in a separate script to test and publish that with the error produced so that we can reproduce the problem, something like
require "active_record"
ActiveRecord::Base.establish_connection(
adapter: "sqlite3",
database: "./image.db"
)
if !ActiveRecord::Base.connection.table_exists?('SRCS')
ActiveRecord::Schema.define do
create_table 'SRCS' do |table|
table.column :account, :string
table.column :url, :string
end
end
end
class Src < ActiveRecord::Base
self.table_name = 'SRCS'
end
p Src.first