Adjust exception handling for post-deploy prepare class

`PostDeployMigrations::Prepare` class raises an exception when on
pending post-migrations are available or when the production checks
fail. The exception is not useful:

* Release managers can't take any action from it, in most of the cases,
  they'll need to wait for a resolution.
* We don't raise exceptions on auto-deploy operations when production
  checks fail. We just notify release managers about it.

This commit updates the way the `Prepare` classes handles exception by:

* Sending a message when there are no pending post-migrations
* Catch the exception when there are no pending post-migrations and when
  production health checks fail
* It still sends a message when production checks fail.

The job that invokes the prepare class will still fail.

As part of gitlab-com/gl-infra/delivery#2441

lib/release_tools/auto_deploy/post_deploy_migrations/prepare.rb

@@ -17,7 +17,9 @@ module ReleaseTools
           if pending_post_migrations.empty?
             logger.warn('No pending post migrations to be executed, skipping execution')
 
-            raise NoPendingPostMigrationsError, 'no pending post migrations'
+            send_no_pending_post_migration_message
+
+            raise NoPendingPostMigrationsError, 'no pending post-migrations'
           end
 
           logger.info('Pending post migrations present, executing the post-deploy pipeline', post_migrations: pending_post_migrations)
@@ -25,6 +27,10 @@ module ReleaseTools
           check_production_status
 
           post_note_to_release_issue(pending_post_migrations)
+
+          true
+        rescue NoPendingPostMigrationsError, UnsafeProductionError
+          false
         end
 
         private
@@ -33,6 +39,10 @@ module ReleaseTools
           PostDeployMigrations::Pending.new.execute
         end
 
+        def send_no_pending_post_migration_message
+          initial_notification.no_pending_post_migrations_message
+        end
+
         def post_note_to_release_issue(pending_post_migrations)
           ReleaseNote.new(production_status, pending_post_migrations).execute
         end
@@ -41,9 +51,9 @@ module ReleaseTools
           if production_status.fine?
             logger.info('Production checks have succeeded, proceeding with post-deploy migrations')
           else
-            logger.warn('Production checks have failed', production_checks: failed_checks)
+            logger.warn('Production checks have failed')
 
-            send_slack_message unless SharedStatus.dry_run?
+            initial_notification.production_status_message(production_status)
 
             raise UnsafeProductionError, 'production checks have failed'
           end
@@ -53,36 +63,8 @@ module ReleaseTools
           @production_status ||= ReleaseTools::Promotion::ProductionStatus.new(:canary_up, :active_deployments)
         end
 
-        def send_slack_message
-          Retriable.retriable do
-            ReleaseTools::Slack::ChatopsNotification.fire_hook(
-              text: text_message,
-              channel: ReleaseTools::Slack::F_UPCOMING_RELEASE,
-              blocks: foreword_slack_blocks + production_status.to_slack_blocks
-            )
-          end
-        end
-
-        def failed_checks
-          production_status.failed_checks.collect(&:to_s)
-        end
-
-        def text_message
-          'Post-deployment migrations are blocked'
-        end
-
-        def foreword_slack_blocks
-          text = StringIO.new
-          text.puts(":red_circle: #{release_managers_mention} #{text_message}")
-          text.puts
-
-          blocks = ::Slack::BlockKit.blocks
-          blocks.section { |block| block.mrkdwn(text: text.string) }
-          blocks.as_json
-        end
-
-        def release_managers_mention
-          "<!subteam^#{ReleaseTools::Slack::RELEASE_MANAGERS}>"
+        def initial_notification
+          ReleaseTools::Slack::PostDeployPipelineInitialNotification.new
         end
       end
     end

lib/release_tools/slack.rb

@@ -12,6 +12,7 @@ require 'release_tools/slack/chatops_notification'
 require 'release_tools/slack/merge_train_notification'
 require 'release_tools/slack/message'
 require 'release_tools/slack/post_deploy_migrations_notification'
+require 'release_tools/slack/post_deploy_pipeline_initial_notification'
 require 'release_tools/slack/qa_notification'
 require 'release_tools/slack/search'
 require 'release_tools/slack/tag_notification'

lib/release_tools/slack/post_deploy_pipeline_initial_notification.rb

+# frozen_string_literal: true
+
+module ReleaseTools
+  module Slack
+    class PostDeployPipelineInitialNotification
+      def no_pending_post_migrations_message
+        return if SharedStatus.dry_run?
+
+        message =
+          'No pending post migrations available, skipping post-deploy pipeline execution'
+
+        foreword_message = ":ci_passed_with_warnings #{message}"
+
+        blocks = foreword_slack_blocks(foreword_message)
+
+        send_chatops_notification(message, blocks)
+      end
+
+      def production_status_message(production_status)
+        return if SharedStatus.dry_run?
+
+        message = 'Post-deployment pipeline is blocked'
+
+        foreword_message =
+          ":red_circle: #{release_managers_mention} #{message}"
+
+        blocks =
+          foreword_slack_blocks(foreword_message) + production_status.to_slack_blocks
+
+        send_chatops_notification(message, blocks)
+      end
+
+      private
+
+      def no_pending_post_migrations
+        'No pending post migrations available, skipping post-deploy pipeline execution'
+      end
+
+      def foreword_slack_blocks(message)
+        text = StringIO.new
+        text.puts(message)
+        text.puts
+
+        blocks = ::Slack::BlockKit.blocks
+        blocks.section { |block| block.mrkdwn(text: text.string) }
+        blocks.as_json
+      end
+
+      def release_managers_mention
+        "<!subteam^#{ReleaseTools::Slack::RELEASE_MANAGERS}>"
+      end
+
+      def send_chatops_notification(text, blocks)
+        Retriable.retriable do
+          ReleaseTools::Slack::ChatopsNotification.fire_hook(
+            text: text,
+            channel: ReleaseTools::Slack::F_UPCOMING_RELEASE,
+            blocks: blocks
+          )
+        end
+      end
+    end
+  end
+end

lib/tasks/post_deploy_migrations.rake

@@ -12,7 +12,9 @@ namespace :post_deploy_migrations do
 
   desc 'Performs production checks before executing the post-deployment migrations, and posts note to monthly release issue'
   task :prepare do
-    ReleaseTools::AutoDeploy::PostDeployMigrations::Prepare.new.execute
+    prepare = ReleaseTools::AutoDeploy::PostDeployMigrations::Prepare.new
+
+    raise 'Skipping post-deploy pipeline execution' unless prepare.execute
   end
 
   desc 'Builds post-migrations artifacts'

spec/lib/release_tools/auto_deploy/post_deploy_migrations/prepare_spec.rb

@@ -3,9 +3,6 @@
 require 'spec_helper'
 
 describe ReleaseTools::AutoDeploy::PostDeployMigrations::Prepare do
-  let(:healthy) { true }
-  let(:failed_checks) { [] }
-
   let(:post_migrations) do
     [
       '20220510192117_foo.rb',
@@ -17,12 +14,14 @@ describe ReleaseTools::AutoDeploy::PostDeployMigrations::Prepare do
     double('ReleaseTools::AutoDeploy::PostDeployMigrations::ReleaseNote')
   end
 
+  let(:notification) do
+    double('ReleaseTools::Slack::PostDeployPipelineInitialNotification')
+  end
+
   let(:production_status) do
     instance_spy(
       ReleaseTools::Promotion::ProductionStatus,
-      fine?: healthy,
-      failed_checks: failed_checks,
-      to_slack_blocks: ['production status']
+      fine?: true
     )
   end
 
@@ -47,88 +46,38 @@ describe ReleaseTools::AutoDeploy::PostDeployMigrations::Prepare do
     allow(ReleaseTools::AutoDeploy::PostDeployMigrations::ReleaseNote)
       .to receive(:new)
       .and_return(release_note)
+
+    allow(ReleaseTools::Slack::PostDeployPipelineInitialNotification)
+      .to receive(:new)
+      .and_return(notification)
   end
 
   describe '#execute' do
     context 'with pending post migrations' do
-      it 'verifies the production checks and posts a note to the release issue' do
+      it 'proceeds to execute the post-deploy pipeline' do
         expect(production_status).to receive(:fine?)
         expect(release_note).to receive(:execute)
 
-        prepare.execute
+        expect(prepare.execute).to be_truthy
       end
 
       context 'when production is unhealthy' do
-        shared_examples 'skips post-deploy pipeline execution' do
-          let(:healthy) { false }
-
-          let(:slack_message) do
-            [
-              {
-                type: 'section',
-                text: {
-                  type: 'mrkdwn',
-                  text: ":red_circle: <!subteam^S0127FU8PDE> Post-deployment migrations are blocked\n\n"
-                }
-              }
-            ]
-          end
-
-          before do
-            allow(ReleaseTools::Slack::ChatopsNotification)
-              .to receive(:fire_hook)
-          end
-
-          it 'notifies release managers and raises exception' do
-            expect(ReleaseTools::Slack::ChatopsNotification)
-              .to receive(:fire_hook)
-              .with(
-                blocks: slack_message + ['production status'],
-                text: 'Post-deployment migrations are blocked',
-                channel: ReleaseTools::Slack::F_UPCOMING_RELEASE
-              )
-
-            expect do
-              without_dry_run { prepare.execute }
-            end.to raise_error('production checks have failed')
-          end
-
-          it 'skips posting a note on the release issue' do
-            expect(release_note).not_to receive(:execute)
-
-            expect do
-              prepare.execute
-            end.to raise_error('production checks have failed')
-          end
-
-          context 'with dry run' do
-            it 'does not post to Slack and raises error' do
-              expect(ReleaseTools::Slack::ChatopsNotification)
-                .not_to receive(:fire_hook)
-
-              expect do
-                prepare.execute
-              end.to raise_error('production checks have failed')
-            end
-          end
+        let(:production_status) do
+          instance_spy(
+            ReleaseTools::Promotion::ProductionStatus,
+            fine?: false,
+            to_slack_blocks: ['production status']
+          )
         end
 
-        it_behaves_like 'skips post-deploy pipeline execution'
+        it 'skips post-deploy pipeline execution' do
+          expect(notification)
+            .to receive(:production_status_message)
+            .with(production_status)
 
-        context 'with active incidents' do
-          let(:failed_checks) do
-            [ReleaseTools::Promotion::Checks::ActiveIncidents]
-          end
+          expect(release_note).not_to receive(:execute)
 
-          it_behaves_like 'skips post-deploy pipeline execution'
-        end
-
-        context 'with active deployments' do
-          let(:failed_checks) do
-            [ReleaseTools::Promotion::Checks::ActiveDeployments]
-          end
-
-          it_behaves_like 'skips post-deploy pipeline execution'
+          expect(prepare.execute).to be_falsy
         end
       end
     end
@@ -136,10 +85,13 @@ describe ReleaseTools::AutoDeploy::PostDeployMigrations::Prepare do
     context 'without pending post-migrations' do
       let(:post_migrations) { [] }
 
-      it 'raises an error' do
-        expect do
-          prepare.execute
-        end.to raise_error('no pending post migrations')
+      it 'skips post-deploy pipeline execution' do
+        expect(notification)
+          .to receive(:no_pending_post_migrations_message)
+
+        expect(release_note).not_to receive(:execute)
+
+        expect(prepare.execute).to be_falsy
       end
     end
   end

spec/lib/release_tools/slack/post_deploy_pipeline_initial_notification_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe ReleaseTools::Slack::PostDeployPipelineInitialNotification do
+  subject(:initial_notification) { described_class.new }
+
+  before do
+    allow(ReleaseTools::Slack::ChatopsNotification)
+      .to receive(:fire_hook)
+      .and_return({})
+  end
+
+  describe '#no_pending_post_migration_message' do
+    it 'sends a chatops message' do
+      block_message =
+        ":ci_passed_with_warnings No pending post migrations available, skipping post-deploy pipeline execution\n\n"
+
+      expect(ReleaseTools::Slack::ChatopsNotification)
+        .to receive(:fire_hook)
+        .with(
+          text: 'No pending post migrations available, skipping post-deploy pipeline execution',
+          channel: ReleaseTools::Slack::F_UPCOMING_RELEASE,
+          blocks: slack_mrkdwn_block(text: block_message)
+        )
+
+      without_dry_run do
+        initial_notification.no_pending_post_migrations_message
+      end
+    end
+
+    context 'with dry-run' do
+      it 'skips sending a message' do
+        expect(ReleaseTools::Slack::Message)
+          .not_to receive(:post)
+
+        initial_notification.no_pending_post_migrations_message
+      end
+    end
+  end
+
+  describe '#production_status_message' do
+    let(:production_status) do
+      instance_double(
+        ReleaseTools::Promotion::ProductionStatus,
+        {
+          to_slack_blocks: ['blocks']
+        }
+      )
+    end
+
+    it 'sends a chatops message' do
+      block_message =
+        ":red_circle: <!subteam^#{ReleaseTools::Slack::RELEASE_MANAGERS}> Post-deployment pipeline is blocked\n\n"
+
+      expect(ReleaseTools::Slack::ChatopsNotification)
+        .to receive(:fire_hook)
+        .with(
+          text: 'Post-deployment pipeline is blocked',
+          channel: ReleaseTools::Slack::F_UPCOMING_RELEASE,
+          blocks: slack_mrkdwn_block(text: block_message) + ['blocks']
+        )
+
+      without_dry_run do
+        initial_notification.production_status_message(production_status)
+      end
+    end
+
+    context 'with a dry-run' do
+      it 'skips sending a message' do
+        expect(ReleaseTools::Slack::ChatopsNotification)
+          .not_to receive(:fire_hook)
+
+        initial_notification.production_status_message(production_status)
+      end
+    end
+  end
+end