Remove issues from old index

ee/elastic/migrate/20210112165500_delete_issues_from_original_index.rb

+# frozen_string_literal: true
+
+class DeleteIssuesFromOriginalIndex < Elastic::Migration
+  batched!
+  throttle_delay 1.minute
+
+  MAX_ATTEMPTS = 30
+
+  QUERY_BODY = {
+                 query: {
+                   term: {
+                     type: 'issue'
+                   }
+                 }
+               }.freeze
+
+  def migrate
+    retry_attempt = migration_state[:retry_attempt].to_i
+
+    if retry_attempt >= MAX_ATTEMPTS
+      fail_migration_halt_error!(retry_attempt: retry_attempt)
+      return
+    end
+
+    if completed?
+      log "Skipping removing issues from the original index since it is already applied"
+      return
+    end
+
+    response = client.delete_by_query(index: helper.target_name, body: QUERY_BODY)
+
+    log_raise "Failed to delete issues: #{response['failures']}" if response['failures'].present?
+  rescue StandardError => e
+    log "migrate failed, increasing migration_state retry_attempt: #{retry_attempt} error:#{e.class}:#{e.message}"
+
+    set_migration_state(
+      retry_attempt: retry_attempt + 1
+    )
+
+    raise e
+  end
+
+  def completed?
+    helper.refresh_index
+
+    results = client.search(index: helper.target_name, body: QUERY_BODY.merge(size: 0))
+    results.dig('hits', 'total', 'value') == 0
+  end
+end

ee/spec/elastic/migrate/20210112165500_delete_issues_from_original_index_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require File.expand_path('ee/elastic/migrate/20210112165500_delete_issues_from_original_index.rb')
+
+RSpec.describe DeleteIssuesFromOriginalIndex, :elastic, :sidekiq_inline do
+  let(:version) { 20210112165500 }
+  let(:migration) { described_class.new(version) }
+  let(:helper) { Gitlab::Elastic::Helper.new }
+
+  before do
+    stub_ee_application_setting(elasticsearch_search: true, elasticsearch_indexing: true)
+    allow(migration).to receive(:helper).and_return(helper)
+  end
+
+  describe 'migration_options' do
+    it 'has migration options set', :aggregate_failures do
+      expect(migration.batched?).to be_truthy
+      expect(migration.throttle_delay).to eq(1.minute)
+    end
+  end
+
+  context 'issues are already deleted' do
+    it 'does not execute delete_by_query' do
+      expect(migration.completed?).to be_truthy
+      expect(helper.client).not_to receive(:delete_by_query)
+
+      migration.migrate
+    end
+  end
+
+  context 'issues are still present in the index' do
+    let(:issues) { create_list(:issue, 3) }
+
+    before do
+      allow(Elastic::DataMigrationService).to receive(:migration_has_finished?)
+        .with(:migrate_issues_to_separate_index)
+        .and_return(false)
+
+      # ensure issues are indexed
+      issues
+
+      ensure_elasticsearch_index!
+    end
+
+    it 'removes issues from the index' do
+      expect { migration.migrate }.to change { migration.completed? }.from(false).to(true)
+    end
+  end
+
+  context 'migration fails' do
+    let(:client) { double('Elasticsearch::Transport::Client') }
+
+    before do
+      allow(migration).to receive(:client).and_return(client)
+      allow(migration).to receive(:completed?).and_return(false)
+    end
+
+    context 'exception is raised' do
+      before do
+        allow(client).to receive(:delete_by_query).and_raise(StandardError)
+      end
+
+      it 'increases retry_attempt' do
+        migration.set_migration_state(retry_attempt: 1)
+
+        expect { migration.migrate }.to raise_error(StandardError)
+        expect(migration.migration_state).to match(retry_attempt: 2)
+      end
+
+      it 'fails the migration after too many attempts' do
+        migration.set_migration_state(retry_attempt: 30)
+
+        migration.migrate
+
+        expect(migration.migration_state).to match(retry_attempt: 30, halted: true, halted_indexing_unpaused: false)
+        expect(client).not_to receive(:delete_by_query)
+      end
+    end
+
+    context 'es responds with errors' do
+      before do
+        allow(client).to receive(:delete_by_query).and_return('failures' => ['failed'])
+      end
+
+      it 'raises an error and increases retry attempt' do
+        expect { migration.migrate }.to raise_error(/Failed to delete issues/)
+        expect(migration.migration_state).to match(retry_attempt: 1)
+      end
+    end
+  end
+end