Follow logs of a specific container

lib/kamal/cli/app.rb

@@ -195,12 +195,14 @@ class Kamal::Cli::App < Kamal::Cli::Base
   option :grep_options, aliases: "-o", desc: "Additional options supplied to grep"
   option :follow, aliases: "-f", desc: "Follow log on primary server (or specific host set by --hosts)"
   option :skip_timestamps, type: :boolean, aliases: "-T", desc: "Skip appending timestamps to logging output"
+  option :container_id, desc: "Docker container ID to fetch logs"
   def logs
     # FIXME: Catch when app containers aren't running
 
     grep = options[:grep]
     grep_options = options[:grep_options]
     since = options[:since]
+    container_id = options[:container_id]
     timestamps = !options[:skip_timestamps]
 
     if options[:follow]
@@ -213,8 +215,8 @@ class Kamal::Cli::App < Kamal::Cli::Base
         role = KAMAL.roles_on(KAMAL.primary_host).first
 
         app = KAMAL.app(role: role, host: host)
-        info app.follow_logs(host: KAMAL.primary_host, timestamps: timestamps, lines: lines, grep: grep, grep_options: grep_options)
+        info app.follow_logs(host: KAMAL.primary_host, timestamps: timestamps, lines: lines, grep: grep, grep_options: grep_options, container_id: container_id)
-        exec app.follow_logs(host: KAMAL.primary_host, timestamps: timestamps, lines: lines, grep: grep, grep_options: grep_options)
+        exec app.follow_logs(host: KAMAL.primary_host, timestamps: timestamps, lines: lines, grep: grep, grep_options: grep_options, container_id: container_id)
       end
     else
       lines = options[:lines].presence || ((since || grep) ? nil : 100) # Default to 100 lines if since or grep isn't set

lib/kamal/commands/app/logging.rb

@@ -6,10 +6,10 @@ module Kamal::Commands::App::Logging
       ("grep '#{grep}'#{" #{grep_options}" if grep_options}" if grep)
   end
 
-  def follow_logs(host:, timestamps: true, lines: nil, grep: nil, grep_options: nil)
+  def follow_logs(host:, timestamps: true, lines: nil, grep: nil, grep_options: nil, container_id: nil)
     run_over_ssh \
       pipe(
-        current_running_container_id,
+        container_id ? "echo #{container_id}" : current_running_container_id,
         "xargs docker logs#{" --timestamps" if timestamps}#{" --tail #{lines}" if lines} --follow 2>&1",
         (%(grep "#{grep}"#{" #{grep_options}" if grep_options}) if grep)
       ),

test/cli/app_test.rb

@@ -353,6 +353,13 @@ class CliAppTest < CliTestCase
     assert_match "sh -c '\\''docker ps --latest --quiet --filter label=service=app --filter label=destination= --filter label=role=web --filter status=running --filter status=restarting --filter ancestor=$(docker image ls --filter reference=dhh/app:latest --format '\\''\\'\\'''\\''{{.ID}}'\\''\\'\\'''\\'') ; docker ps --latest --quiet --filter label=service=app --filter label=destination= --filter label=role=web --filter status=running --filter status=restarting'\\'' | head -1 | xargs docker logs --timestamps --tail 10 --follow 2>&1", run_command("logs", "--follow")
   end
 
+  test "logs with follow and container_id" do
+    SSHKit::Backend::Abstract.any_instance.stubs(:exec)
+      .with("ssh -t root@1.1.1.1 -p 22 'echo ID123 | xargs docker logs --timestamps --tail 10 --follow 2>&1'")
+
+    assert_match "echo ID123 | xargs docker logs --timestamps --tail 10 --follow 2>&1", run_command("logs", "--follow", "--container_id", "ID123")
+  end
+
   test "logs with follow and grep" do
     SSHKit::Backend::Abstract.any_instance.stubs(:exec)
       .with("ssh -t root@1.1.1.1 -p 22 'sh -c '\\''docker ps --latest --quiet --filter label=service=app --filter label=destination= --filter label=role=web --filter status=running --filter status=restarting --filter ancestor=$(docker image ls --filter reference=dhh/app:latest --format '\\''\\'\\'''\\''{{.ID}}'\\''\\'\\'''\\'') ; docker ps --latest --quiet --filter label=service=app --filter label=destination= --filter label=role=web --filter status=running --filter status=restarting'\\'' | head -1 | xargs docker logs --timestamps --follow 2>&1 | grep \"hey\"'")

test/commands/app_test.rb

@@ -208,6 +208,10 @@ class CommandsAppTest < ActiveSupport::TestCase
       "ssh -t root@app-1 -p 22 'sh -c '\\''docker ps --latest --quiet --filter label=service=app --filter label=destination= --filter label=role=web --filter status=running --filter status=restarting --filter ancestor=$(docker image ls --filter reference=dhh/app:latest --format '\\''\\'\\'''\\''{{.ID}}'\\''\\'\\'''\\'') ; docker ps --latest --quiet --filter label=service=app --filter label=destination= --filter label=role=web --filter status=running --filter status=restarting'\\'' | head -1 | xargs docker logs --timestamps --follow 2>&1 | grep \"Completed\"'",
       new_command.follow_logs(host: "app-1", grep: "Completed")
 
+    assert_equal \
+      "ssh -t root@app-1 -p 22 'echo ID321 | xargs docker logs --timestamps --follow 2>&1'",
+      new_command.follow_logs(host: "app-1", container_id: "ID321")
+
     assert_equal \
       "ssh -t root@app-1 -p 22 'sh -c '\\''docker ps --latest --quiet --filter label=service=app --filter label=destination= --filter label=role=web --filter status=running --filter status=restarting --filter ancestor=$(docker image ls --filter reference=dhh/app:latest --format '\\''\\'\\'''\\''{{.ID}}'\\''\\'\\'''\\'') ; docker ps --latest --quiet --filter label=service=app --filter label=destination= --filter label=role=web --filter status=running --filter status=restarting'\\'' | head -1 | xargs docker logs --timestamps --tail 123 --follow 2>&1'",
       new_command.follow_logs(host: "app-1", lines: 123)