Merge branch '21170-cycle-analytics' into 'master'

Cycle Analytics: first iteration

## What does this MR do?

- Implement the first iteration of the "Cycle Analytics" feature.

## What are the relevant issue numbers?

- Closes #21170 

## Screenshots

![cycle_analytics_screencast.gif](/uploads/d23c3c912caa6935fd47b53ca3a56b97/cycle_analytics.gif)

## Backend Tasks

- [x]  Implementation
    - [x]  Phases
        - [x]  Issue (Tracker)
        - [x]  Plan (Board)
        - [x]  Code (IDE)
        - [x]  Test (CI)
        - [x]  Review (MR)
        - [x]  Staging (CD)
        - [x]  Production (Total)
    - [x]  Make heuristics more modular
    - [x]  Scope to project
    - [x]  Date range (30 days, 90 days)
    - [x]  Access restriction
- [x]  Test
    - [x]  Find a better way to test these phases
    - [x]  Phases
        - [x]  Issue (Tracker)
        - [x]  Plan (Board)
        - [x]  Code (IDE)
        - [x]  Test (CI)
        - [x]  Review (MR)
        - [x]  Staging (CD)
        - [x]  Production (Total)
    - [x]  Test for "end case happens before start case"
    - [x]  Consolidate helper
- [x]  Miniboss review
- [x]  Performance testing with mock data
- [x]  Improve performance
    - [x]  Pre-calculate "merge requests closing issues
    - [x]  Pre-calculate everything else
- [x]  Test performance against 10k issues
- [x]  Test all pre-calculation code
    - [x]  Ci::Pipeline -> build start/finish
    - [x]  Ci::Pipeline#merge_requests
    - [x]  Issue -> record default metrics after save
    - [x]  MergeRequest -> record default metrics after save
    - [x]  Deployment -> Update "first_deployed_to_production_at" for MR metrics
    - [x]  Git Push -> Update "first commit mention" for issue metrics
    - [x]  Merge request create/update/refresh -> Update "merge requests closing issues"
- [x]  Remove `MergeRequestsClosingIssues` when necessary
- [x]  Changes to unblock Fatih
    - [x]  Add summary data
    - [x]  `stats` should be array
    - [x]  Let `stats` be `null` if all `stats` are null
- [x]  Indexes for "merge requests closing issues"
- [x]  Test summary data
- [x]  Scope everything to project
    - [x]  Find out why tests were passing
- [x]  Filter should include issues/MRs which have made it to production within the range
- [x]  Don't create duplicate `MergeRequestsClosingIssues`
- [x]  Fix tests
- [x]  MySQL median
- [x]  Assign to Douwe for review
- [x]  Fix conflicts
- [x]  Implement suggestions from Yorick's review
    - [x]  Test on PG
    - [x]  Test on MySQL
- [x]  Refactor
    - [x]  Cleanup
        - [x]  What happens if we have no data at all?
        - [x]  Extract common queries to methods / scopes
    - [x]  Remove unused queries
    - [x]  Downtime for foreign key migrations
    - [x]  Find a way around "if issue.metrics.present?" all over the place
    - [x]  Find a way around "if merge_request.metrics.present?" all over the place
    - [x]  Test migrations on a fresh database
        - [x]  MySQL
        - [x]  Pg
- [x]  Access issues
    - While the project is public and the visibility is set to "Everyone with access", you cannot visit the cycle analytics page when signed out.
- [x]  CHANGELOG
- [x]  Implement suggestions from Douwe's review
    - [x]  First set of comments
    - [x]  Second set of comments
    - [x]  Third set of comments
    - [x]  Fourth set of comments
- [x]  Make sure build is green
- [ ]  Make issue for "polish"
- [ ]  EE MR


See merge request !5986

CHANGELOG

@@ -22,6 +22,7 @@ v 8.12.0 (unreleased)
   - Pass the "Remember me" value to the U2F authentication form
   - Display stages in valid order in stages dropdown on build page
   - Only update projects.last_activity_at once per hour when creating a new event
+  - Cycle analytics (first iteration) !5986
   - Remove vendor prefixes for linear-gradient CSS (ClemMakesApps)
   - Move pushes_since_gc from the database to Redis
   - Add font color contrast to external label in admin area (ClemMakesApps)

Gemfile

@@ -320,6 +320,7 @@ group :test do
   gem 'webmock', '~> 1.21.0'
   gem 'test_after_commit', '~> 0.4.2'
   gem 'sham_rack', '~> 1.3.6'
+  gem 'timecop', '~> 0.8.0'
 end
 group :production do

Gemfile.lock

@@ -980,6 +980,7 @@ DEPENDENCIES
   teaspoon-jasmine (~> 2.2.0)
   test_after_commit (~> 0.4.2)
   thin (~> 1.7.0)
+  timecop (~> 0.8.0)
   turbolinks (~> 2.5.0)
   u2f (~> 0.2.1)
   uglifier (~> 2.7.2)

app/assets/javascripts/cycle-analytics.js.es6

+((global) => {
+
+  const COOKIE_NAME = 'cycle_analytics_help_dismissed';
+
+  gl.CycleAnalytics = class CycleAnalytics {
+    constructor() {
+      const that = this;
+
+      this.isHelpDismissed = $.cookie(COOKIE_NAME);
+      this.vue = new Vue({
+        el: '#cycle-analytics',
+        name: 'CycleAnalytics',
+        created: this.fetchData(),
+        data: this.decorateData({ isLoading: true }),
+        methods: {
+          dismissLanding() {
+            that.dismissLanding();
+          }
+        }
+      });
+    }
+
+    fetchData(options) {
+      options = options || { startDate: 30 };
+
+      $.ajax({
+        url: $('#cycle-analytics').data('request-path'),
+        method: 'GET',
+        dataType: 'json',
+        contentType: 'application/json',
+        data: { start_date: options.startDate }
+      }).done((data) => {
+        this.vue.$data = this.decorateData(data);
+        this.initDropdown();
+      })
+      .error((data) => {
+        this.handleError(data);
+      })
+      .always(() => {
+        this.vue.isLoading = false;
+      })
+    }
+
+    decorateData(data) {
+      data.summary = data.summary || [];
+      data.stats = data.stats || [];
+      data.isHelpDismissed = this.isHelpDismissed;
+      data.isLoading = data.isLoading || false;
+
+      data.summary.forEach((item) => {
+        item.value = item.value || '-';
+      });
+
+      data.stats.forEach((item) => {
+        item.value = item.value || '- - -';
+      })
+
+      return data;
+    }
+
+    handleError(data) {
+      this.vue.$data = {
+        hasError: true,
+        isHelpDismissed: this.isHelpDismissed
+      };
+
+      new Flash('There was an error while fetching cycle analytics data.', 'alert');
+    }
+
+    dismissLanding() {
+      this.vue.isHelpDismissed = true;
+      $.cookie(COOKIE_NAME, true);
+    }
+
+    initDropdown() {
+      const $dropdown = $('.js-ca-dropdown');
+      const $label = $dropdown.find('.dropdown-label');
+
+      $dropdown.find('li a').off('click').on('click', (e) => {
+        e.preventDefault();
+        const $target = $(e.currentTarget);
+        const value = $target.data('value');
+
+        $label.text($target.text().trim());
+        this.vue.isLoading = true;
+        this.fetchData({ startDate: value });
+      })
+    }
+
+  }
+
+})(window.gl || (window.gl = {}));

app/assets/javascripts/dispatcher.js

@@ -94,6 +94,11 @@
           break;
         case "projects:merge_requests:conflicts":
           window.mcui = new MergeConflictResolver()
+          break;
+        case 'projects:merge_requests:index':
+          shortcut_handler = new ShortcutsNavigation();
+          Issuable.init();
+          break;
         case 'dashboard:activity':
           new Activities();
           break;
@@ -185,6 +190,9 @@
           new gl.ProtectedBranchCreate();
           new gl.ProtectedBranchEditList();
           break;
+        case 'projects:cycle_analytics:show':
+          new gl.CycleAnalytics();
+          break;
       }
       switch (path.first()) {
         case 'admin':

app/assets/stylesheets/pages/cycle_analytics.scss

+#cycle-analytics {
+  margin: 24px auto 0;
+  width: 800px;
+  position: relative;
+
+  .panel {
+
+    .content-block {
+      padding: 24px 0;
+      border-bottom: none;
+      position: relative;
+    }
+
+    .column {
+      text-align: center;
+
+      .header {
+        font-size: 30px;
+        line-height: 38px;
+        font-weight: normal;
+        margin: 0;
+      }
+
+      .text {
+        color: $layout-link-gray;
+        margin: 0;
+      }
+
+      &:last-child {
+        text-align: right;
+      }
+    }
+
+    .dropdown {
+      position: relative;
+      top: 13px;
+    }
+  }
+
+  .bordered-box {
+    border: 1px solid $border-color;
+    @include border-radius($border-radius-default);
+    position: relative;
+  }
+
+  .content-list {
+    li {
+      padding: 18px $gl-padding $gl-padding;
+
+      .container-fluid {
+        padding: 0;
+      }
+    }
+
+    .title-col {
+      p {
+        margin: 0;
+
+        &.title {
+          line-height: 19px;
+          font-size: 15px;
+          font-weight: 600;
+        }
+        &:text {
+          color: #8c8c8c;
+        }
+      }
+    }
+
+    .value-col {
+      text-align: right;
+
+      span {
+        line-height: 42px;
+      }
+    }
+  }
+
+  .landing {
+    margin-bottom: $gl-padding;
+    overflow: hidden;
+
+    .dismiss-icon {
+      position: absolute;
+      right: $gl-padding;
+      cursor: pointer;
+      color: #b2b2b2;
+    }
+
+    svg {
+      margin: 0 20px;
+      float: left;
+      width: 136px;
+      height: 136px;
+    }
+
+    .inner-content {
+      width: 480px;
+      float: left;
+
+      h4 {
+        color: $gl-text-color;
+        font-size: 17px;
+      }
+
+      p {
+        color: #8c8c8c;
+        margin-bottom: $gl-padding;
+      }
+    }
+  }
+
+  .fa-spinner {
+    font-size: 28px;
+    position: relative;
+    margin-left: -20px;
+    left: 50%;
+    margin-top: 36px;
+  }
+
+}

app/controllers/projects/cycle_analytics_controller.rb

+class Projects::CycleAnalyticsController < Projects::ApplicationController
+  include ActionView::Helpers::DateHelper
+  include ActionView::Helpers::TextHelper
+
+  before_action :authorize_read_cycle_analytics!
+
+  def show
+    @cycle_analytics = CycleAnalytics.new(@project, from: parse_start_date)
+
+    respond_to do |format|
+      format.html
+      format.json { render json: cycle_analytics_json }
+    end
+  end
+
+  private
+
+  def parse_start_date
+    case cycle_analytics_params[:start_date]
+    when '30' then 30.days.ago
+    when '90' then 90.days.ago
+    else 90.days.ago
+    end
+  end
+
+  def cycle_analytics_params
+    return {} unless params[:cycle_analytics].present?
+
+    { start_date: params[:cycle_analytics][:start_date] }
+  end
+
+  def cycle_analytics_json
+    cycle_analytics_view_data = [[:issue, "Issue", "Time before an issue gets scheduled"],
+                                 [:plan, "Plan", "Time before an issue starts implementation"],
+                                 [:code, "Code", "Time until first merge request"],
+                                 [:test, "Test", "Total test time for all commits/merges"],
+                                 [:review, "Review", "Time between merge request creation and merge/close"],
+                                 [:staging, "Staging", "From merge request merge until deploy to production"],
+                                 [:production, "Production", "From issue creation until deploy to production"]]
+
+    stats = cycle_analytics_view_data.reduce([]) do |stats, (stage_method, stage_text, stage_description)|
+      value = @cycle_analytics.send(stage_method).presence
+
+      stats << {
+        title: stage_text,
+        description: stage_description,
+        value: value && !value.zero? ? distance_of_time_in_words(value) : nil
+      }
+      stats
+    end
+
+    issues = @cycle_analytics.summary.new_issues
+    commits = @cycle_analytics.summary.commits
+    deploys = @cycle_analytics.summary.deploys
+
+    summary = [
+      { title: "New Issue".pluralize(issues), value: issues },
+      { title: "Commit".pluralize(commits), value: commits },
+      { title: "Deploy".pluralize(deploys), value: deploys }
+    ]
+
+    {
+      summary: summary,
+      stats: stats
+    }
+  end
+end

app/helpers/gitlab_routing_helper.rb

@@ -46,6 +46,10 @@ module GitlabRoutingHelper
     namespace_project_environments_path(project.namespace, project, *args)
   end
+  def project_cycle_analytics_path(project, *args)
+    namespace_project_cycle_analytics_path(project.namespace, project, *args)
+  end
+
   def project_builds_path(project, *args)
     namespace_project_builds_path(project.namespace, project, *args)
   end

app/models/ci/pipeline.rb

@@ -56,6 +56,16 @@ module Ci
         pipeline.finished_at = Time.now
       end
+      after_transition [:created, :pending] => :running do |pipeline|
+        MergeRequest::Metrics.where(merge_request_id: pipeline.merge_requests.map(&:id)).
+          update_all(latest_build_started_at: pipeline.started_at, latest_build_finished_at: nil)
+      end
+
+      after_transition any => [:success] do |pipeline|
+        MergeRequest::Metrics.where(merge_request_id: pipeline.merge_requests.map(&:id)).
+          update_all(latest_build_finished_at: pipeline.finished_at)
+      end
+
       before_transition do |pipeline|
         pipeline.update_duration
       end
@@ -280,6 +290,16 @@ module Ci
       project.execute_services(data, :pipeline_hooks)
     end
+    # Merge requests for which the current pipeline is running against
+    # the merge request's latest commit.
+    def merge_requests
+      @merge_requests ||=
+        begin
+          project.merge_requests.where(source_branch: self.ref).
+            select { |merge_request| merge_request.pipeline.try(:id) == self.id }
+        end
+    end
+
     private
     def pipeline_data

app/models/concerns/issuable.rb

@@ -28,10 +28,13 @@ module Issuable
         loaded? && to_a.all? { |note| note.association(:award_emoji).loaded? }
       end
     end
+
     has_many :label_links, as: :target, dependent: :destroy
     has_many :labels, through: :label_links
     has_many :todos, as: :target, dependent: :destroy
+    has_one :metrics
+
     validates :author, presence: true
     validates :title, presence: true, length: { within: 0..255 }
@@ -81,6 +84,7 @@ module Issuable
     acts_as_paranoid
     after_save :update_assignee_cache_counts, if: :assignee_id_changed?
+    after_save :record_metrics
     def update_assignee_cache_counts
       # make sure we flush the cache for both the old *and* new assignee
@@ -286,4 +290,9 @@ module Issuable
   def can_move?(*)
     false
   end
+
+  def record_metrics
+    metrics = self.metrics || create_metrics
+    metrics.record!
+  end
 end

app/models/cycle_analytics.rb

+class CycleAnalytics
+  include Gitlab::Database::Median
+  include Gitlab::Database::DateTime
+
+  def initialize(project, from:)
+    @project = project
+    @from = from
+  end
+
+  def summary
+    @summary ||= Summary.new(@project, from: @from)
+  end
+
+  def issue
+    calculate_metric(:issue,
+                     Issue.arel_table[:created_at],
+                     [Issue::Metrics.arel_table[:first_associated_with_milestone_at],
+                      Issue::Metrics.arel_table[:first_added_to_board_at]])
+  end
+
+  def plan
+    calculate_metric(:plan,
+                     [Issue::Metrics.arel_table[:first_associated_with_milestone_at],
+                      Issue::Metrics.arel_table[:first_added_to_board_at]],
+                     Issue::Metrics.arel_table[:first_mentioned_in_commit_at])
+  end
+
+  def code
+    calculate_metric(:code,
+                     Issue::Metrics.arel_table[:first_mentioned_in_commit_at],
+                     MergeRequest.arel_table[:created_at])
+  end
+
+  def test
+    calculate_metric(:test,
+                     MergeRequest::Metrics.arel_table[:latest_build_started_at],
+                     MergeRequest::Metrics.arel_table[:latest_build_finished_at])
+  end
+
+  def review
+    calculate_metric(:review,
+                     MergeRequest.arel_table[:created_at],
+                     MergeRequest::Metrics.arel_table[:merged_at])
+  end
+
+  def staging
+    calculate_metric(:staging,
+                     MergeRequest::Metrics.arel_table[:merged_at],
+                     MergeRequest::Metrics.arel_table[:first_deployed_to_production_at])
+  end
+
+  def production
+    calculate_metric(:production,
+                     Issue.arel_table[:created_at],
+                     MergeRequest::Metrics.arel_table[:first_deployed_to_production_at])
+  end
+
+  private
+
+  def calculate_metric(name, start_time_attrs, end_time_attrs)
+    cte_table = Arel::Table.new("cte_table_for_#{name}")
+
+    # Build a `SELECT` query. We find the first of the `end_time_attrs` that isn't `NULL` (call this end_time).
+    # Next, we find the first of the start_time_attrs that isn't `NULL` (call this start_time).
+    # We compute the (end_time - start_time) interval, and give it an alias based on the current
+    # cycle analytics stage.
+    interval_query = Arel::Nodes::As.new(
+      cte_table,
+      subtract_datetimes(base_query, end_time_attrs, start_time_attrs, name.to_s))
+
+    median_datetime(cte_table, interval_query, name)
+  end
+
+  # Join table with a row for every <issue,merge_request> pair (where the merge request
+  # closes the given issue) with issue and merge request metrics included. The metrics
+  # are loaded with an inner join, so issues / merge requests without metrics are
+  # automatically excluded.
+  def base_query
+    arel_table = MergeRequestsClosingIssues.arel_table
+
+    # Load issues
+    query = arel_table.join(Issue.arel_table).on(Issue.arel_table[:id].eq(arel_table[:issue_id])).
+            join(Issue::Metrics.arel_table).on(Issue.arel_table[:id].eq(Issue::Metrics.arel_table[:issue_id])).
+            where(Issue.arel_table[:project_id].eq(@project.id)).
+            where(Issue.arel_table[:deleted_at].eq(nil)).
+            where(Issue.arel_table[:created_at].gteq(@from))
+
+    # Load merge_requests
+    query = query.join(MergeRequest.arel_table, Arel::Nodes::OuterJoin).
+            on(MergeRequest.arel_table[:id].eq(arel_table[:merge_request_id])).
+            join(MergeRequest::Metrics.arel_table).
+            on(MergeRequest.arel_table[:id].eq(MergeRequest::Metrics.arel_table[:merge_request_id]))
+
+    # Limit to merge requests that have been deployed to production after `@from`
+    query.where(MergeRequest::Metrics.arel_table[:first_deployed_to_production_at].gteq(@from))
+  end
+end

app/models/cycle_analytics/summary.rb

+class CycleAnalytics
+  class Summary
+    def initialize(project, from:)
+      @project = project
+      @from = from
+    end
+
+    def new_issues
+      @project.issues.created_after(@from).count
+    end
+
+    def commits
+      repository = @project.repository.raw_repository
+
+      if @project.default_branch
+        repository.log(ref: @project.default_branch, after: @from).count
+      end
+    end
+
+    def deploys
+      @project.deployments.where("created_at > ?", @from).count
+    end
+  end
+end

app/models/deployment.rb

@@ -42,4 +42,38 @@ class Deployment < ActiveRecord::Base
     project.repository.is_ancestor?(commit.id, sha)
   end
+
+  def update_merge_request_metrics!
+    return unless environment.update_merge_request_metrics?
+
+    merge_requests = project.merge_requests.
+                     joins(:metrics).
+                     where(target_branch: self.ref, merge_request_metrics: { first_deployed_to_production_at: nil }).
+                     where("merge_request_metrics.merged_at <= ?", self.created_at)
+
+    if previous_deployment
+      merge_requests = merge_requests.where("merge_request_metrics.merged_at >= ?", previous_deployment.created_at)
+    end
+
+    # Need to use `map` instead of `select` because MySQL doesn't allow `SELECT`ing from the same table
+    # that we're updating.
+    merge_request_ids =
+      if Gitlab::Database.postgresql?
+        merge_requests.select(:id)
+      elsif Gitlab::Database.mysql?
+        merge_requests.map(&:id)
+      end
+
+    MergeRequest::Metrics.
+      where(merge_request_id: merge_request_ids, first_deployed_to_production_at: nil).
+      update_all(first_deployed_to_production_at: self.created_at)
+  end
+
+  def previous_deployment
+    @previous_deployment ||=
+      project.deployments.joins(:environment).
+      where(environments: { name: self.environment.name }, ref: self.ref).
+      where.not(id: self.id).
+      take
+  end
 end

app/models/environment.rb

@@ -43,4 +43,8 @@ class Environment < ActiveRecord::Base
     last_deployment.includes_commit?(commit)
   end
+
+  def update_merge_request_metrics?
+    self.name == "production"
+  end
 end

app/models/issue.rb

@@ -23,6 +23,8 @@ class Issue < ActiveRecord::Base
   has_many :events, as: :target, dependent: :destroy
+  has_many :merge_requests_closing_issues, class_name: 'MergeRequestsClosingIssues', dependent: :delete_all
+
   validates :project, presence: true
   scope :cared, ->(user) { where(assignee_id: user) }
@@ -36,6 +38,8 @@ class Issue < ActiveRecord::Base
   scope :order_due_date_asc, -> { reorder('issues.due_date IS NULL, issues.due_date ASC') }
   scope :order_due_date_desc, -> { reorder('issues.due_date IS NULL, issues.due_date DESC') }
+  scope :created_after, -> (datetime) { where("created_at >= ?", datetime) }
+
   attr_spammable :title, spam_title: true
   attr_spammable :description, spam_description: true

app/models/issue/metrics.rb

+class Issue::Metrics < ActiveRecord::Base
+  belongs_to :issue
+
+  def record!
+    if issue.milestone_id.present? && self.first_associated_with_milestone_at.blank?
+      self.first_associated_with_milestone_at = Time.now
+    end
+
+    if issue_assigned_to_list_label? && self.first_added_to_board_at.blank?
+      self.first_added_to_board_at = Time.now
+    end
+
+    self.save
+  end
+
+  private
+
+  def issue_assigned_to_list_label?
+    issue.labels.any? { |label| label.lists.present? }
+  end
+end

app/models/merge_request.rb

@@ -16,6 +16,8 @@ class MergeRequest < ActiveRecord::Base
   has_many :events, as: :target, dependent: :destroy
+  has_many :merge_requests_closing_issues, class_name: 'MergeRequestsClosingIssues', dependent: :delete_all
+
   serialize :merge_params, Hash
   after_create :ensure_merge_request_diff, unless: :importing?
@@ -501,6 +503,19 @@ class MergeRequest < ActiveRecord::Base
     target_project
   end
+  # If the merge request closes any issues, save this information in the
+  # `MergeRequestsClosingIssues` model. This is a performance optimization.
+  # Calculating this information for a number of merge requests requires
+  # running `ReferenceExtractor` on each of them separately.
+  def cache_merge_request_closes_issues!(current_user = self.author)
+    transaction do
+      self.merge_requests_closing_issues.delete_all
+      closes_issues(current_user).each do |issue|
+        self.merge_requests_closing_issues.create!(issue: issue)
+      end
+    end
+  end
+
   def closes_issue?(issue)
     closes_issues.include?(issue)
   end
@@ -508,7 +523,8 @@ class MergeRequest < ActiveRecord::Base
   # Return the set of issues that will be closed if this merge request is accepted.
   def closes_issues(current_user = self.author)
     if target_branch == project.default_branch
-      messages = commits.map(&:safe_message) << description
+      messages = [description]
+      messages.concat(commits.map(&:safe_message)) if merge_request_diff
       Gitlab::ClosingIssueExtractor.new(project, current_user).
         closed_by_message(messages.join("\n"))

app/models/merge_request/metrics.rb

+class MergeRequest::Metrics < ActiveRecord::Base
+  belongs_to :merge_request
+
+  def record!
+    if merge_request.merged? && self.merged_at.blank?
+      self.merged_at = Time.now
+    end
+
+    self.save
+  end
+end

app/models/merge_requests_closing_issues.rb

+class MergeRequestsClosingIssues < ActiveRecord::Base
+  belongs_to :merge_request
+  belongs_to :issue
+
+  validates :merge_request_id, uniqueness: { scope: :issue_id }, presence: true
+  validates :issue_id, presence: true
+end

app/policies/project_policy.rb

@@ -46,6 +46,7 @@ class ProjectPolicy < BasePolicy
     can! :create_issue
     can! :create_note
     can! :upload_file
+    can! :read_cycle_analytics
   end
   def reporter_access!
@@ -204,6 +205,7 @@ class ProjectPolicy < BasePolicy
     can! :read_commit_status
     can! :read_container_image
     can! :download_code
+    can! :read_cycle_analytics
     # NOTE: may be overridden by IssuePolicy
     can! :read_issue