Delete merge requests from original ES index

ee/app/models/elastic/migration_record.rb

@@ -6,6 +6,8 @@ module Elastic
 
     delegate :migrate, :skip_migration?, :completed?, :batched?, :throttle_delay, :pause_indexing?, :space_requirements?, :space_required_bytes, to: :migration
 
+    ELASTICSEARCH_SIZE = 25
+
     def initialize(version:, name:, filename:)
       @version = version
       @name = name
@@ -57,7 +59,7 @@ module Elastic
     def self.load_versions(completed:)
       helper = Gitlab::Elastic::Helper.default
       helper.client
-            .search(index: helper.migrations_index_name, body: { query: { term: { completed: completed } } })
+            .search(index: helper.migrations_index_name, body: { query: { term: { completed: completed } }, size: ELASTICSEARCH_SIZE })
             .dig('hits', 'hits')
             .map { |v| v['_id'].to_i }
     rescue Elasticsearch::Transport::Transport::Errors::NotFound

ee/changelogs/unreleased/322800-es-migration-to-delete-merge-requests-from-combined-index.yml

+---
+title: Delete Merge Requests from original ES index
+merge_request: 61394
+author:
+type: changed

ee/elastic/migrate/20210510113500_delete_merge_requests_from_original_index.rb

+# frozen_string_literal: true
+
+class DeleteMergeRequestsFromOriginalIndex < Elastic::Migration
+  batched!
+  throttle_delay 3.minutes
+
+  MAX_ATTEMPTS = 30
+
+  QUERY_BODY = {
+    query: {
+      term: {
+        type: 'merge_request'
+      }
+    }
+  }.freeze
+
+  def migrate
+    retry_attempt = migration_state[:retry_attempt].to_i
+    task_id = migration_state[:task_id]
+
+    if retry_attempt >= MAX_ATTEMPTS
+      fail_migration_halt_error!(retry_attempt: retry_attempt)
+      return
+    end
+
+    if task_id
+      log "Checking task status with task_id:#{task_id}"
+      check_task(task_id, retry_attempt)
+      return
+    end
+
+    if completed?
+      log "Skipping removing merge requests from the original index since it is already applied"
+      return
+    end
+
+    log "Launching delete by query"
+    response = client.delete_by_query(index: helper.target_name, body: QUERY_BODY, conflicts: 'proceed', wait_for_completion: false)
+
+    log_raise "Failed to delete merge requests with task_id:#{task_id} - #{response['failures']}" if response['failures'].present?
+
+    task_id = response['task']
+    log "Removing merge requests from the original index is started with task_id:#{task_id}"
+
+    set_migration_state(
+      retry_attempt: retry_attempt,
+      task_id: task_id
+    )
+  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,
+      task_id: nil
+    )
+
+    raise e
+  end
+
+  def completed?
+    helper.refresh_index
+
+    results = client.count(index: helper.target_index_name, body: QUERY_BODY)
+    total_remaining = results.dig('count')
+    log "Checking to see if migration is completed based on index counts remaining:#{total_remaining}"
+
+    total_remaining == 0
+  end
+
+  private
+
+  def check_task(task_id, retry_attempt)
+    response = helper.task_status(task_id: task_id)
+
+    if response['completed']
+      log "Removing merge requests from the original index is completed for task_id:#{task_id}"
+
+      set_migration_state(
+        retry_attempt: retry_attempt,
+        task_id: nil
+      )
+
+      # since delete_by_query is using wait_for_completion = false, the task must be cleaned up
+      # in Elasticsearch system .tasks index
+      helper.client.delete(index: '.tasks', type: 'task', id: task_id)
+    else
+      log "Removing merge requests from the original index is still in progress for task_id:#{task_id}"
+    end
+
+    log_raise "Failed to delete merge requests: #{response['failures']}" if response['failures'].present?
+  end
+end

ee/spec/elastic/migrate/20210510113500_delete_merge_requests_from_original_index_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require File.expand_path('ee/elastic/migrate/20210510113500_delete_merge_requests_from_original_index.rb')
+
+RSpec.describe DeleteMergeRequestsFromOriginalIndex, :elastic, :sidekiq_inline do
+  let(:version) { 20210510113500 }
+  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(3.minutes)
+    end
+  end
+
+  context 'merge requests 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 'merge requests are still present in the index' do
+    let!(:merge_requests) { create_list(:merge_request, 10, :unique_branches) }
+
+    before do
+      set_elasticsearch_migration_to :migrate_merge_requests_to_separate_index, including: false
+      ensure_elasticsearch_index!
+    end
+
+    it 'removes merge requests from the index' do
+      # initiate the task in Elasticsearch
+      migration.migrate
+      expect(migration.migration_state).to match(retry_attempt: 0, task_id: anything)
+      task_id = migration.migration_state[:task_id]
+
+      # the migration might not complete after the initial task is created
+      # so make sure it actually completes
+      50.times do |_| # Max 0.5s waiting
+        migration.migrate
+        break if migration.completed?
+
+        sleep 0.01
+      end
+
+      # verify clean up of the task from Elasticsearch
+      expect(migration.migration_state).to match(retry_attempt: 0, task_id: nil)
+      expect { helper.client.get(index: '.tasks', type: 'task', id: task_id) }.to raise_error(Elasticsearch::Transport::Transport::Errors::NotFound)
+    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, task_id: nil)
+      end
+
+      it 'fails the migration after too many attempts' do
+        stub_const('DeleteMergeRequestsFromOriginalIndex::MAX_ATTEMPTS', 2)
+
+        # run migration up to the set MAX_ATTEMPTS set in the migration
+        DeleteMergeRequestsFromOriginalIndex::MAX_ATTEMPTS.times do
+          expect { migration.migrate }.to raise_error(StandardError)
+        end
+
+        migration.migrate
+
+        expect(migration.migration_state).to match(retry_attempt: 2, task_id: nil, halted: true, halted_indexing_unpaused: false)
+      end
+    end
+
+    context 'es responds with errors' do
+      before do
+        allow(client).to receive(:delete_by_query).and_return('task' => 'task_1')
+      end
+
+      context 'when a task throws an error' do
+        before do
+          allow(helper).to receive(:task_status).and_return('failures' => ['failed'])
+          migration.migrate
+        end
+
+        it 'raises an error and increases retry attempt' do
+          expect { migration.migrate }.to raise_error(/Failed to delete merge requests/)
+          expect(migration.migration_state).to match(retry_attempt: 1, task_id: nil)
+        end
+      end
+
+      context 'when delete_by_query throws an error' 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 merge requests/)
+          expect(migration.migration_state).to match(retry_attempt: 1, task_id: nil)
+        end
+      end
+    end
+  end
+end