Sitemap with Rails and Dokku persistent storage - ruby-on-rails

Question

I'm using sitemap_generator gem to auto-generate the sitemap. It's already configured, tested and it's worked locally, but when I'm in production on my Dokku container, trying to run dokku run tradfood rake -s sitemap:refresh, following lines appear :
City Load (0.7ms) SELECT "cities".* FROM "cities" ORDER BY "cities"."id" ASC LIMIT $1 [["LIMIT", 1000]]
Recipe Load (2.5ms) SELECT "recipes".* FROM "recipes" ORDER BY "recipes"."id" ASC LIMIT $1 [["LIMIT", 1000]]
City Load (8.1ms) SELECT "cities".* FROM "cities" WHERE "cities"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
City Load (1.3ms) SELECT "cities".* FROM "cities" WHERE "cities"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
City Load (0.3ms) SELECT "cities".* FROM "cities" WHERE "cities"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
City Load (0.2ms) SELECT "cities".* FROM "cities" WHERE "cities"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
City Load (0.2ms) SELECT "cities".* FROM "cities" WHERE "cities"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
City Load (0.3ms) SELECT "cities".* FROM "cities" WHERE "cities"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
City Load (0.2ms) SELECT "cities".* FROM "cities" WHERE "cities"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
City Load (0.2ms) SELECT "cities".* FROM "cities" WHERE "cities"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
City Load (0.2ms) SELECT "cities".* FROM "cities" WHERE "cities"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
But nothing has been generated : when I run dokku run tradfood ls -all public, sitemap.xml stay to oct. 21.
My Dokku persistent storage still works with my image uploader on production (it record well new images, using carrierwave).
Here my sitemap.rb configuration :
# Set the host name for URL creation
SitemapGenerator::Sitemap.default_host = "https://tradfood.fr"
SitemapGenerator::Sitemap.create(:compress => false) do
# Put links creation logic here.
#
# The root path '/' and sitemap index file are added automatically for you.
# Links are added to the Sitemap in the order they are specified.
#
# Usage: add(path, options={})
# (default options are used if you don't specify)
#
# Defaults: :priority => 0.5, :changefreq => 'weekly',
# :lastmod => Time.now, :host => default_host
#
# Examples:
#
# Add '/articles'
#
# add articles_path, :priority => 0.7, :changefreq => 'daily'
#
# Add all articles:
#
# Article.find_each do |article|
# add article_path(article), :lastmod => article.updated_at
# end
add '/a-propos', :changefreq => 'monthly'
City.find_each do |city|
add city_path(city.name.parameterize), :lastmod => city.updated_at, :changefreq => 'weekly', :priority => 0.8
end
Recipe.find_each do |recipe|
add recipe_path(recipe.city.name.parameterize, recipe.name.parameterize), :lastmod => recipe.updated_at, :changefreq => 'daily'
end
end

Answer 1

That gist no longer exists. Mind using gist.github.com or pasting it in something native to stackoverflow instead?
I'm guessing:
You are not writing to persistent storage
You are not reading the file from persistent storage