Add "pharos ssh" command to launch ssh into cluster hosts (#581)

lib/pharos/root_command.rb

@@ -4,6 +4,7 @@
 require_relative 'reset_command'
 require_relative 'version_command'
 require_relative 'kubeconfig_command'
+require_relative 'ssh_command'
 
 module Pharos
   class RootCommand < Pharos::Command
@@ -12,7 +13,8 @@ class RootCommand < Pharos::Command
     subcommand ["build", "up"], "initialize/upgrade cluster", UpCommand
     subcommand "kubeconfig", "fetch admin kubeconfig file", KubeconfigCommand
     subcommand "reset", "reset cluster", ResetCommand
-    subcommand ["version"], "show version information", VersionCommand
+    subcommand "ssh", "start an ssh session to a server in a pharos cluster", SSHCommand
+    subcommand "version", "show version information", VersionCommand
 
     def self.run
       super

lib/pharos/ssh_command.rb

@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+
+module Pharos
+  class SSHCommand < UpCommand
+    usage "[OPTIONS] -- [COMMANDS] ..."
+    parameter "[COMMAND] ...", "Run command on host"
+
+    banner "Opens SSH sessions to hosts in the Kontena Pharos cluster."
+
+    option ['-r', '--role'], 'ROLE', 'select a host by role'
+    option ['-l', '--label'], 'LABEL=VALUE', 'select a host by label, can be specified multiple times', multivalued: true do |pair|
+      Hash[*[:key, :value].zip(pair.split('=', 2))]
+    end
+    option ['-a', '--address'], 'ADDRESS', 'select a host by public address'
+
+    option ['-f', '--first'], :flag, 'only perform on the first matching host'
+
+    def hosts
+      @hosts ||= Array(
+        load_config.hosts.send(first? ? :find : :select) do |host|
+          next if role && host.role != role
+          next if address && host.address != address
+
+          unless label_list.empty?
+            next unless label_list.all? { |l| host.labels[l[:key]] == l[:value] }
+          end
+
+          true
+        end
+      ).tap do |result|
+        signal_usage_error 'no host matched in configuration' if result.empty?
+      end
+    end
+
+    def execute
+      exit run_interactive if command_list.empty?
+      exit run_single(hosts.first) if hosts.size == 1
+      exit run_parallel
+    end
+
+    private
+
+    def run_interactive
+      exit_statuses = hosts.map do |host|
+        target = "#{host.user}@#{host.address}"
+        puts pastel.green("==> Opening a session to #{target} ..") unless !$stdout.tty?
+        system('ssh', '-i', host.ssh_key_path, target)
+      end
+      exit_statuses.all?(&:itself) ? 0 : 1
+    end
+
+    def run_single(host)
+      result = ssh_manager.client_for(host).exec(command_list)
+      puts result.output
+      result.exit_status
+    end
+
+    def run_parallel
+      threads = hosts.map do |host|
+        Thread.new do
+          begin
+            [host, ssh_manager.client_for(host).exec(command_list)]
+          rescue StandardError => ex
+            [
+              host,
+              Pharos::SSH::RemoteCommand::Result.new.tap do |r|
+                r.output << ex.message
+              end
+            ]
+          end
+        end
+      end
+      results = threads.map(&:value)
+      results.each do |host, result|
+        puts pastel.send(result.exit_status.zero? ? :green : :red, "==> Result from #{host.user}@#{host.address}")
+        puts result.output.gsub(/^/, "  ")
+      end
+      results.all? { |_, result| result.success? } ? 0 : 1
+    end
+
+    def ssh_manager
+      @ssh_manager ||= Pharos::SSH::Manager.new
+    end
+  end
+end