Extract Slack Notifier functionality into its own class

Author: Daniel Schmidt

lib/beekeeper.rb

@@ -1,5 +1,6 @@
 require 'beekeeper/monkeypatch/docker'
 require 'beekeeper/logging'
+require 'beekeeper/slack_notifier'
 require 'beekeeper/watcher'
 
 module Beekeeper

lib/beekeeper/slack_notifier.rb

@@ -0,0 +1,65 @@
+require 'slack'
+
+module Beekeeper
+  class SlackNotifier
+    # Name of the environment variable containing the string value of
+    # the Slack API/OAuth token.
+    SLACK_TOKEN_ENV = 'SLACK_API_TOKEN'.freeze
+
+    # Name of the environment variable containing the path to file
+    # containing the value of the Slack token. This is used only if
+    # SLACK_TOKEN_ENV is empty.
+    SLACK_TOKEN_FILE_ENV = 'SLACK_API_TOKEN_FILE'.freeze
+
+    # Default path to the file that should contain the Slack token, if
+    # SLACK_TOKEN_ENV and SLACK_TOKEN_FILE_ENV are not set.
+    SLACK_TOKEN_DEFAULT_FILE = '/run/secrets/SLACK_API_TOKEN'.freeze
+
+    attr_reader :client
+
+    def initialize(client = default_client)
+      @client = client
+    end
+
+    def notify_event(event:, recipient:)
+      subject = event.service_name \
+        ? "Service \"#{event.service_name}\" exited #{event.exit_code}"
+        : "Container '#{event.actor.id[..7]}' exited #{event.exit_code}"
+
+      @client.chat_postMessage(
+        channel: recipient,
+        as_user: true,
+        blocks: [
+          { type: 'header', text: { type: 'plain_text', text: subject } },
+          # Event Summary
+          { type: 'section', fields: [{
+              'Host Name'    => Docker.info['Name'],
+              'Swarm Node'   => event.swarm_node_id,
+              'Service Name' => event.service_name,
+              'Container ID' => event.actor_short_id,
+              'Exit Code'    => event.exit_code,
+              'Image'        => event.image_shortname,
+            }.map { |h, t| { type: 'mrkdwn', text: "*#{h}*: #{t}" } }
+          ]},
+          # Container Logs (if available)
+          { type: 'section', text: { type: 'mrkdwn', text: '*Logs:*' } },
+          { type: 'section', text: { type: 'plain_text', text: event.get_logs } },
+        ],
+      )
+    end
+
+    private
+
+    def default_client
+      Slack::Web::Client.new(token: default_token).tap do |client|
+        client.auth_test
+      end
+    end
+
+    def default_token
+      ENV.fetch(SLACK_TOKEN_ENV) do
+        File.read(ENV[SLACK_TOKEN_FILE_ENV] || SLACK_TOKEN_DEFAULT_FILE).chomp
+      end
+    end
+  end
+end

lib/beekeeper/watcher.rb

@@ -1,7 +1,7 @@
 require 'beekeeper/logging'
 require 'beekeeper/monkeypatch/docker'
+require 'beekeeper/slack_notifier'
 require 'docker'
-require 'slack'
 
 module Beekeeper
   class Watcher
@@ -15,19 +15,6 @@ class Watcher
     # still be avoided, as there is a race condition in which events could slip by unnoticed.
     MAX_TIME_BETWEEN_EVENTS = ENV.fetch('READ_TIMEOUT', 0).to_i
 
-    # Name of the environment variable containing the string value of
-    # the Slack API/OAuth token.
-    SLACK_TOKEN_ENV = 'SLACK_API_TOKEN'.freeze
-
-    # Name of the environment variable containing the path to file
-    # containing the value of the Slack token. This is used only if
-    # SLACK_TOKEN_ENV is empty.
-    SLACK_TOKEN_FILE_ENV = 'SLACK_API_TOKEN_FILE'.freeze
-
-    # Default path to the file that should contain the Slack token, if
-    # SLACK_TOKEN_ENV and SLACK_TOKEN_FILE_ENV are not set.
-    SLACK_TOKEN_DEFAULT_FILE = '/run/secrets/SLACK_API_TOKEN'.freeze
-
     # Comma-separated list of Slack channels/users. If a container or
     # service fails and does not have its own custom watchers, these
     # are notified.
@@ -41,8 +28,10 @@ class Watcher
     # of watchers for the service.
     WATCHERS_LABEL = 'beekeeper.watchers'.freeze
 
-    def initialize(slack = nil)
-      @slack = slack || default_slack_client
+    attr_reader :slack
+
+    def initialize(slack = Beekeeper::SlackNotifier.new)
+      @slack = slack
     end
 
     def clean_watchlist(watchlist)
@@ -53,18 +42,6 @@ def clean_watchlist(watchlist)
         .uniq
     end
 
-    def default_slack_client
-      Slack::Web::Client.new(token: default_slack_token).tap do |client|
-        client.auth_test
-      end
-    end
-
-    def default_slack_token
-      ENV.fetch(SLACK_TOKEN_ENV) do
-        File.read(ENV[SLACK_TOKEN_FILE_ENV] || SLACK_TOKEN_DEFAULT_FILE).chomp
-      end
-    end
-
     def default_watchers
       ENV.fetch(WATCHERS_ENV, WATCHERS_DEFAULT).split(',')
     end
@@ -103,30 +80,7 @@ def handle(event)
     end
 
     def notify!(recipient, event)
-      subject = event.service_name \
-        ? "Service \"#{event.service_name}\" exited #{event.exit_code}"
-        : "Container '#{event.actor.id[..7]}' exited #{event.exit_code}"
-
-      @slack.chat_postMessage(
-        channel: recipient,
-        as_user: true,
-        blocks: [
-          { type: 'header', text: { type: 'plain_text', text: subject } },
-          # Event Summary
-          { type: 'section', fields: [{
-              'Host Name'    => Docker.info['Name'],
-              'Swarm Node'   => event.swarm_node_id,
-              'Service Name' => event.service_name,
-              'Container ID' => event.actor_short_id,
-              'Exit Code'    => event.exit_code,
-              'Image'        => event.image_shortname,
-            }.map { |h, t| { type: 'mrkdwn', text: "*#{h}*: #{t}" } }
-          ]},
-          # Container Logs (if available)
-          { type: 'section', text: { type: 'mrkdwn', text: '*Logs:*' } },
-          { type: 'section', text: { type: 'plain_text', text: event.get_logs } },
-        ],
-      )
+      slack.notify_event(event:, recipient:)
     end
 
     def stream_options

spec/slack_notifier_spec.rb

@@ -0,0 +1,51 @@
+require 'beekeeper/slack_notifier'
+require 'docker'
+require 'slack'
+
+describe Beekeeper::SlackNotifier do
+  let(:client) { instance_double(Slack::Web::Client) }
+  subject(:notifier) { Beekeeper::SlackNotifier.new(client) }
+
+  describe 'sending event notifications' do
+    context 'for a failed container' do
+      it 'sends a well-formed chat message' do
+        event = new_event(exit_code: 11)
+        recipient = '#devops-alerts'
+
+        expect(client)
+          .to receive(:chat_postMessage)
+          .with hash_including({
+            channel: recipient,
+            blocks: array_including(hash_including({
+              type: 'header',
+              text: {
+                type: 'plain_text',
+                text: "Container '12345' exited 11"
+              }
+            }))
+          })
+
+        notifier.notify_event event:, recipient:
+      end
+    end
+  end
+
+  def new_event(exit_code: 1, watchers: nil, service_name: nil)
+    attrs = {
+      'exitCode' => exit_code.to_s,
+      'image' => 'containers.lib.berkeley.edu/lap/beekeeper:rspec-tests',
+    }
+    attrs['beekeeper.watchers'] = watchers if watchers
+    attrs['com.docker.swarm.service.name'] = service_name if service_name
+
+    Docker::Event.new(
+      {
+        Action: 'die',
+        Actor: {
+          ID: '12345',
+          Attributes: attrs,
+        },
+      }
+    )
+  end
+end

spec/watcher_spec.rb

@@ -3,55 +3,58 @@
 require 'slack'
 
 describe Beekeeper::Watcher do
-  subject { Beekeeper::Watcher.new(slack) }
+  let(:notifier) { instance_double(Beekeeper::SlackNotifier) }
+  subject(:watcher) { Beekeeper::Watcher.new(notifier) }
 
-  let(:slack) { instance_double(Slack::Web::Client) }
-
-  describe '#watch!' do
-    context 'a container without labels' do
+  describe 'watching failure events' do
+    context 'for an unlabeled container' do
       before { @old_watchers = ENV.delete('BEEKEEPER_WATCHERS') }
       after { ENV['BEEKEEPER_WATCHERS'] = @old_watchers }
 
       it 'notifies default channels' do
-        expect_docker_event new_event
-        expect_slack_notifications %w(#devops-alerts)
+        event = new_event
+        recipients = %w(#devops-alerts)
+        expect_docker_event event
+        expect_event_notification(event:, recipients:)
 
-        subject.watch!
+        watcher.watch!
       end
     end
 
-    context 'a container with labels' do
+    context 'for a container with labels' do
       it 'notifies the correct channels' do
-        expect_docker_event new_event(watchers: '@some-user,#some-channel')
-        expect_slack_notifications %w(#some-channel @some-user)
+        recipients = %w(#some-channel @some-user)
+        event = new_event(watchers: recipients)
+        expect_docker_event event
+        expect_event_notification(event:, recipients:)
 
-        subject.watch!
+        watcher.watch!
       end
     end
   end
 
-  def expect_slack_notifications(channels)
-    channels.each do |channel|
-      expect(slack)
-        .to receive(:chat_postMessage)
-        .once
-        .ordered
-        .with(hash_including(channel: channel))
-    end
-  end
+  private
 
   def expect_docker_event(event)
     expect(Docker::Event)
       .to receive(:stream)
       .and_yield(event)
   end
 
+  def expect_event_notification(event:, recipients:)
+    recipients.each do |recipient|
+      expect(notifier)
+        .to receive(:notify_event)
+        .with(event:, recipient:)
+    end
+  end
+
   def new_event(exit_code: 1, watchers: nil, service_name: nil)
     attrs = {
       'exitCode' => exit_code.to_s,
       'image' => 'containers.lib.berkeley.edu/lap/beekeeper:rspec-tests',
     }
-    attrs['beekeeper.watchers'] = watchers if watchers
+    attrs['beekeeper.watchers'] = watchers.join(',') if watchers
     attrs['com.docker.swarm.service.name'] = service_name if service_name
 
     Docker::Event.new(