Use local docker registry to push and pull app images

Allow applications to be deployed without needing to set up a repository
in a remote Docker registry.

If the registry server starts with `localhost`, Kamal will start a local
docker registry on that port and push the app image to it.

Then when pulling the image onto the servers, we use net-ssh to forward
the that port from the app server to the deployment server.

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
       - name: Setup Ruby and install gems
         uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 3.3.0
+          ruby-version: 3.4.1
           bundler-cache: true
       - name: Run Rubocop
         run: bundle exec rubocop --parallel
@@ -28,7 +28,7 @@ jobs:
           - "3.1"
           - "3.2"
           - "3.3"
-          - "3.4.0-preview2"
+          - "3.4"
         gemfile:
           - Gemfile
           - gemfiles/rails_edge.gemfile

Gemfile.lock

@@ -16,23 +16,23 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
-    actionpack (8.0.0.1)
-      actionview (= 8.0.0.1)
-      activesupport (= 8.0.0.1)
+    actionpack (8.0.1)
+      actionview (= 8.0.1)
+      activesupport (= 8.0.1)
       nokogiri (>= 1.8.5)
       rack (>= 2.2.4)
       rack-session (>= 1.0.1)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
       useragent (~> 0.16)
-    actionview (8.0.0.1)
-      activesupport (= 8.0.0.1)
+    actionview (8.0.1)
+      activesupport (= 8.0.1)
       builder (~> 3.1)
       erubi (~> 1.11)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
-    activesupport (8.0.0.1)
+    activesupport (8.0.1)
       base64
       benchmark (>= 0.3)
       bigdecimal
@@ -48,32 +48,30 @@ GEM
     ast (2.4.2)
     base64 (0.2.0)
     bcrypt_pbkdf (1.1.1)
-    bcrypt_pbkdf (1.1.1-arm64-darwin)
-    bcrypt_pbkdf (1.1.1-x86_64-darwin)
     benchmark (0.4.0)
-    bigdecimal (3.1.8)
+    bigdecimal (3.1.9)
     builder (3.3.0)
     concurrent-ruby (1.3.4)
-    connection_pool (2.4.1)
+    connection_pool (2.5.0)
     crass (1.0.6)
     date (3.4.1)
-    debug (1.9.2)
+    debug (1.10.0)
       irb (~> 1.10)
       reline (>= 0.3.8)
-    dotenv (3.1.5)
+    dotenv (3.1.7)
     drb (2.2.1)
     ed25519 (1.3.0)
-    erubi (1.13.0)
+    erubi (1.13.1)
     i18n (1.14.6)
       concurrent-ruby (~> 1.0)
     io-console (0.8.0)
-    irb (1.14.2)
+    irb (1.14.3)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
-    json (2.9.0)
+    json (2.9.1)
     language_server-protocol (3.17.0.3)
-    logger (1.6.3)
-    loofah (2.23.1)
+    logger (1.6.5)
+    loofah (2.24.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
     minitest (5.25.4)
@@ -84,25 +82,26 @@ GEM
     net-sftp (4.0.0)
       net-ssh (>= 5.0.0, < 8.0.0)
     net-ssh (7.3.0)
-    nokogiri (1.17.2-arm64-darwin)
+    nokogiri (1.18.1-arm64-darwin)
       racc (~> 1.4)
-    nokogiri (1.17.2-x86_64-darwin)
+    nokogiri (1.18.1-x86_64-darwin)
       racc (~> 1.4)
-    nokogiri (1.17.2-x86_64-linux)
+    nokogiri (1.18.1-x86_64-linux-gnu)
       racc (~> 1.4)
     ostruct (0.6.1)
     parallel (1.26.3)
     parser (3.3.6.0)
       ast (~> 2.4.1)
       racc
-    psych (5.2.1)
+    psych (5.2.2)
       date
       stringio
     racc (1.8.1)
     rack (3.1.8)
-    rack-session (2.0.0)
+    rack-session (2.1.0)
+      base64 (>= 0.1.0)
       rack (>= 3.0.0)
-    rack-test (2.1.0)
+    rack-test (2.2.0)
       rack (>= 1.3)
     rackup (2.2.1)
       rack (>= 3)
@@ -113,22 +112,22 @@ GEM
     rails-html-sanitizer (1.6.2)
       loofah (~> 2.21)
       nokogiri (>= 1.15.7, != 1.16.7, != 1.16.6, != 1.16.5, != 1.16.4, != 1.16.3, != 1.16.2, != 1.16.1, != 1.16.0.rc1, != 1.16.0)
-    railties (8.0.0.1)
-      actionpack (= 8.0.0.1)
-      activesupport (= 8.0.0.1)
+    railties (8.0.1)
+      actionpack (= 8.0.1)
+      activesupport (= 8.0.1)
       irb (~> 1.13)
       rackup (>= 1.0.0)
       rake (>= 12.2)
       thor (~> 1.0, >= 1.2.2)
       zeitwerk (~> 2.6)
     rainbow (3.1.1)
     rake (13.2.1)
-    rdoc (6.8.1)
+    rdoc (6.10.0)
       psych (>= 4.0.0)
-    regexp_parser (2.9.3)
-    reline (0.5.12)
+    regexp_parser (2.10.0)
+    reline (0.6.0)
       io-console (~> 0.5)
-    rubocop (1.69.2)
+    rubocop (1.70.0)
       json (~> 2.3)
       language_server-protocol (>= 3.17.0)
       parallel (~> 1.10)
@@ -138,15 +137,15 @@ GEM
       rubocop-ast (>= 1.36.2, < 2.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 2.4.0, < 4.0)
-    rubocop-ast (1.36.2)
+    rubocop-ast (1.37.0)
       parser (>= 3.3.1.0)
     rubocop-minitest (0.36.0)
       rubocop (>= 1.61, < 2.0)
       rubocop-ast (>= 1.31.1, < 2.0)
-    rubocop-performance (1.23.0)
+    rubocop-performance (1.23.1)
       rubocop (>= 1.48.1, < 2.0)
       rubocop-ast (>= 1.31.1, < 2.0)
-    rubocop-rails (2.27.0)
+    rubocop-rails (2.28.0)
       activesupport (>= 4.2.0)
       rack (>= 1.1)
       rubocop (>= 1.52.0, < 2.0)
@@ -158,7 +157,7 @@ GEM
       rubocop-rails
     ruby-progressbar (1.13.0)
     ruby2_keywords (0.0.5)
-    securerandom (0.4.0)
+    securerandom (0.4.1)
     sshkit (1.23.2)
       base64
       net-scp (>= 1.1.2)
@@ -169,7 +168,7 @@ GEM
     thor (1.3.2)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
-    unicode-display_width (3.1.2)
+    unicode-display_width (3.1.4)
       unicode-emoji (~> 4.0, >= 4.0.4)
     unicode-emoji (4.0.4)
     uri (1.0.2)
@@ -189,4 +188,4 @@ DEPENDENCIES
   rubocop-rails-omakase
 
 BUNDLED WITH
-   2.4.3
+   2.6.2

lib/kamal/cli/build.rb

@@ -60,14 +60,16 @@ def push
 
   desc "pull", "Pull app image from registry onto servers"
   def pull
-    if (first_hosts = mirror_hosts).any?
-      #  Pull on a single host per mirror first to seed them
-      say "Pulling image on #{first_hosts.join(", ")} to seed the #{"mirror".pluralize(first_hosts.count)}...", :magenta
-      pull_on_hosts(first_hosts)
-      say "Pulling image on remaining hosts...", :magenta
-      pull_on_hosts(KAMAL.hosts - first_hosts)
-    else
-      pull_on_hosts(KAMAL.hosts)
+    Kamal::Cli::PortForwarding.new(KAMAL.hosts, KAMAL.config.registry.local_port).forward do
+      if (first_hosts = mirror_hosts).any?
+        #  Pull on a single host per mirror first to seed them
+        say "Pulling image on #{first_hosts.join(", ")} to seed the #{"mirror".pluralize(first_hosts.count)}...", :magenta
+        pull_on_hosts(first_hosts)
+        say "Pulling image on remaining hosts...", :magenta
+        pull_on_hosts(KAMAL.hosts - first_hosts)
+      else
+        pull_on_hosts(KAMAL.hosts)
+      end
     end
   end
 

lib/kamal/cli/main.rb

@@ -22,7 +22,7 @@ def deploy
       invoke_options = deploy_options
 
       say "Log into image registry...", :magenta
-      invoke "kamal:cli:registry:login", [], invoke_options.merge(skip_local: options[:skip_push])
+      invoke "kamal:cli:registry:setup", [], invoke_options.merge(skip_local: options[:skip_push])
 
       if options[:skip_push]
         say "Pull app image...", :magenta
@@ -184,7 +184,7 @@ def remove
         invoke "kamal:cli:app:remove", [], options.without(:confirmed)
         invoke "kamal:cli:proxy:remove", [], options.without(:confirmed)
         invoke "kamal:cli:accessory:remove", [ "all" ], options
-        invoke "kamal:cli:registry:logout", [], options.without(:confirmed).merge(skip_local: true)
+        invoke "kamal:cli:registry:remove", [], options.without(:confirmed).merge(skip_local: true)
       end
     end
   end

lib/kamal/cli/port_forwarding.rb

@@ -0,0 +1,44 @@
+class Kamal::Cli::PortForwarding
+  attr_reader :hosts, :port
+
+  def initialize(hosts, port)
+    @hosts = hosts
+    @port = port
+  end
+
+  def forward
+    if KAMAL.config.registry.local?
+      @done = false
+      forward_ports
+    end
+
+    yield
+  ensure
+    stop
+  end
+
+  private
+
+  def stop
+    @done = true
+    @threads.to_a.each(&:join)
+  end
+
+  def forward_ports
+    @threads = hosts.map do |host|
+      Thread.new do
+        Net::SSH.start(host, KAMAL.config.ssh.user) do |ssh|
+          ssh.forward.remote(port, "localhost", port, "localhost")
+          ssh.loop(0.1) do
+            if @done
+              ssh.forward.cancel_remote(port, "localhost")
+              break
+            else
+              true
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/kamal/cli/registry.rb

@@ -1,17 +1,25 @@
 class Kamal::Cli::Registry < Kamal::Cli::Base
-  desc "login", "Log in to registry locally and remotely"
+  desc "setup", "Setup local registry or log in to remote registry locally and remotely"
   option :skip_local, aliases: "-L", type: :boolean, default: false, desc: "Skip local login"
   option :skip_remote, aliases: "-R", type: :boolean, default: false, desc: "Skip remote login"
-  def login
-    run_locally    { execute *KAMAL.registry.login } unless options[:skip_local]
-    on(KAMAL.hosts) { execute *KAMAL.registry.login } unless options[:skip_remote]
+  def setup
+    if KAMAL.registry.local?
+      run_locally    { execute *KAMAL.registry.setup } unless options[:skip_local]
+    else
+      run_locally    { execute *KAMAL.registry.login } unless options[:skip_local]
+      on(KAMAL.hosts) { execute *KAMAL.registry.login } unless options[:skip_remote]
+    end
   end
 
-  desc "logout", "Log out of registry locally and remotely"
+  desc "remove", "Remove local registry or log out of remote registry locally and remotely"
   option :skip_local, aliases: "-L", type: :boolean, default: false, desc: "Skip local login"
   option :skip_remote, aliases: "-R", type: :boolean, default: false, desc: "Skip remote login"
-  def logout
-    run_locally    { execute *KAMAL.registry.logout } unless options[:skip_local]
-    on(KAMAL.hosts) { execute *KAMAL.registry.logout } unless options[:skip_remote]
+  def remove
+    if KAMAL.registry.local?
+      run_locally    { execute *KAMAL.registry.remove, raise_on_non_zero_exit: false } unless options[:skip_local]
+    else
+      run_locally    { execute *KAMAL.registry.logout } unless options[:skip_local]
+      on(KAMAL.hosts) { execute *KAMAL.registry.logout } unless options[:skip_remote]
+    end
   end
 end

lib/kamal/commands/builder/local.rb

@@ -1,6 +1,15 @@
 class Kamal::Commands::Builder::Local < Kamal::Commands::Builder::Base
   def create
-    docker :buildx, :create, "--name", builder_name, "--driver=#{driver}" unless docker_driver?
+    return if docker_driver?
+
+    options =
+      if KAMAL.registry.local?
+        "--driver=#{driver} --driver-opt network=host"
+      else
+        "--driver=#{driver}"
+      end
+
+    docker :buildx, :create, "--name", builder_name, options
   end
 
   def remove
@@ -9,6 +18,10 @@ def remove
 
   private
     def builder_name
-      "kamal-local-#{driver}"
+      if KAMAL.registry.local?
+        "kamal-local-registry-#{driver}"
+      else
+        "kamal-local-#{driver}"
+      end
     end
 end

lib/kamal/commands/registry.rb

@@ -1,7 +1,10 @@
 class Kamal::Commands::Registry < Kamal::Commands::Base
   delegate :registry, to: :config
+  delegate :local?, :local_port, to: :registry
 
   def login
+    return if local?
+
     docker :login,
       registry.server,
       "-u", sensitive(Kamal::Utils.escape_shell_value(registry.username)),
@@ -11,4 +14,18 @@ def login
   def logout
     docker :logout, registry.server
   end
+
+  def setup
+    combine \
+      docker(:start, "kamal-docker-registry"),
+      docker(:run, "--detach", "-p", "127.0.0.1:#{local_port}:5000", "--name", "kamal-docker-registry", "registry:2"),
+      by: "||"
+  end
+
+  def remove
+    combine \
+      docker(:stop, "kamal-docker-registry"),
+      docker(:rm, "kamal-docker-registry"),
+      by: "&&"
+  end
 end

lib/kamal/configuration/registry.rb

@@ -21,6 +21,14 @@ def password
     lookup("password")
   end
 
+  def local?
+    server&.match?("^localhost[:$]")
+  end
+
+  def local_port
+    local? ? (server.split(":").last.to_i || 80) : nil
+  end
+
   private
     def lookup(key)
       if registry_config[key].is_a?(Array)