FEATURE: experimental hidden setting for draft backups

Under exceptional situations the automatic draft feature can fail.

This new **hidden, default off** site setting
`backup_drafts_to_pm_length` will automatically backup any draft that is
saved by the system to a dedicated PM (originating from self)

The body of that PM will contain the text of the reply.

We can enable this feature strategically on sites exhibiting issues to
diagnose issues with the draft system and offer a recourse to users who
appear to lose drafts. We automatically checkpoint these drafts every 5
minutes forcing a new revision each 5 minutes so you can revert to old
content.

Longer term we are considering automatically enabling this kind of feature
for extremely long drafts where the risk is really high one could lose
days of writing.

app/models/backup_draft_post.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class BackupDraftPost < ActiveRecord::Base
+  belongs_to :user
+  belongs_to :post
+end
+
+# == Schema Information
+#
+# Table name: backup_draft_posts
+#
+#  id         :bigint           not null, primary key
+#  user_id    :integer          not null
+#  post_id    :integer          not null
+#  key        :string           not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+# Indexes
+#
+#  index_backup_draft_posts_on_post_id          (post_id) UNIQUE
+#  index_backup_draft_posts_on_user_id_and_key  (user_id,key) UNIQUE
+#

app/models/backup_draft_topic.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class BackupDraftTopic < ActiveRecord::Base
+  belongs_to :user
+  belongs_to :topic
+end
+
+# == Schema Information
+#
+# Table name: backup_draft_topics
+#
+#  id         :bigint           not null, primary key
+#  user_id    :integer          not null
+#  topic_id   :integer          not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+# Indexes
+#
+#  index_backup_draft_topics_on_topic_id  (topic_id) UNIQUE
+#  index_backup_draft_topics_on_user_id   (user_id) UNIQUE
+#

app/models/draft.rb

@@ -6,6 +6,10 @@ class Draft < ActiveRecord::Base
   EXISTING_TOPIC ||= 'topic_'
 
   def self.set(user, key, sequence, data)
+    if SiteSetting.backup_drafts_to_pm_length > 0 && SiteSetting.backup_drafts_to_pm_length < data.length
+      backup_draft(user, key, sequence, data)
+    end
+
     if d = find_draft(user, key)
       return if d.sequence > sequence
 
@@ -96,6 +100,92 @@ class Draft < ActiveRecord::Base
     Draft.where("updated_at < ?", delete_drafts_older_than_n_days).destroy_all
   end
 
+  def self.backup_draft(user, key, sequence, data)
+    reply = JSON.parse(data)["reply"] || ""
+    return if reply.length < SiteSetting.backup_drafts_to_pm_length
+
+    post_id = BackupDraftPost.where(user_id: user.id, key: key).pluck(:post_id).first
+    post = Post.where(id: post_id).first if post_id
+
+    if post_id && !post
+      BackupDraftPost.where(user_id: user.id, key: key).delete_all
+    end
+
+    indented_reply = reply.split("\n").map! do |l|
+      "    #{l}"
+    end
+    draft_body = <<~MD
+      #{indented_reply.join("\n")}
+
+      ```text
+      seq: #{sequence}
+      key: #{key}
+      ```
+    MD
+
+    return if post && post.raw == draft_body
+
+    if !post
+      topic = ensure_draft_topic!(user)
+      Post.transaction do
+        post = PostCreator.new(
+          user,
+          raw: draft_body,
+          skip_jobs: true,
+          skip_validations: true,
+          topic_id: topic.id,
+        ).create
+        BackupDraftPost.create!(user_id: user.id, key: key, post_id: post.id)
+      end
+    elsif post.updated_at > 5.minutes.ago
+      # bypass all validations here to maximize speed
+      post.update_columns(
+        raw: draft_body,
+        cooked: PrettyText.cook(draft_body),
+        updated_at: Time.zone.now
+      )
+    else
+      revisor = PostRevisor.new(post, post.topic)
+      revisor.revise!(user, { raw: draft_body },
+        bypass_bump: true,
+        skip_validations: true,
+        skip_staff_log: true,
+        bypass_rate_limiter: true
+      )
+    end
+
+  rescue => e
+    Discourse.warn_exception(e, message: "Failed to backup draft")
+  end
+
+  def self.ensure_draft_topic!(user)
+    topic_id = BackupDraftTopic.where(user_id: user.id).pluck(:topic_id).first
+    topic = Topic.find_by(id: topic_id) if topic_id
+
+    if topic_id && !topic
+      BackupDraftTopic.where(user_id: user.id).delete_all
+    end
+
+    if !topic
+      Topic.transaction do
+        creator = PostCreator.new(
+          user,
+          title: I18n.t("draft_backup.pm_title"),
+          archetype: Archetype.private_message,
+          raw: I18n.t("draft_backup.pm_body"),
+          skip_jobs: true,
+          skip_validations: true,
+          target_usernames: user.username
+        )
+        topic = creator.create.topic
+        BackupDraftTopic.create!(topic_id: topic.id, user_id: user.id)
+      end
+    end
+
+    topic
+
+  end
+
 end
 
 # == Schema Information

config/locales/server.en.yml

@@ -871,6 +871,9 @@ en:
       short_description: "Like this post"
       long_form: "liked this"
 
+  draft_backup:
+    pm_title: "Backup Drafts from ongoing topics"
+    pm_body: "Topic containing backup drafts"
   user_activity:
     no_default:
       self: "You have no activity yet."
@@ -1993,7 +1996,7 @@ en:
     notify_about_flags_after: "If there are flags that haven't been handled after this many hours, send a personal message to moderators. Set to 0 to disable."
     show_create_topics_notice: "If the site has fewer than 5 public topics, show a notice asking admins to create some topics."
 
-    delete_drafts_older_than_n_days: Delete drafts older than (n) days.
+    delete_drafts_older_than_n_days: "Delete drafts older than (n) days."
 
     bootstrap_mode_min_users: "Minimum number of users required to disable bootstrap mode (set to 0 to disable)"
 

config/site_settings.yml

@@ -1858,6 +1858,10 @@ uncategorized:
   delete_drafts_older_than_n_days:
     default: 180
 
+  backup_drafts_to_pm_length:
+    default: 0
+    hidden: true
+
   tos_topic_id:
     default: -1
     hidden: true

db/migrate/20191017044811_add_draft_backup_tables.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class AddDraftBackupTables < ActiveRecord::Migration[6.0]
+  def change
+
+    create_table :backup_draft_topics do |t|
+      t.integer :user_id, null: false
+      t.integer :topic_id, null: false
+      t.timestamps
+    end
+
+    create_table :backup_draft_posts do |t|
+      t.integer :user_id, null: false
+      t.integer :post_id, null: false
+      t.string :key, null: false
+      t.timestamps
+    end
+
+    add_index :backup_draft_posts, [:user_id, :key], unique: true
+    add_index :backup_draft_posts, [:post_id], unique: true
+
+    add_index :backup_draft_topics, [:user_id], unique: true
+    add_index :backup_draft_topics, [:topic_id], unique: true
+  end
+end

lib/post_creator.rb

@@ -34,6 +34,7 @@ class PostCreator
   #                             dequeue before the commit finishes. If you do this, be sure to
   #                             call `enqueue_jobs` after the transaction is comitted.
   #   hidden_reason_id        - Reason for hiding the post (optional)
+  #   skip_validations        - Do not validate any of the content in the post
   #
   #   When replying to a topic:
   #     topic_id              - topic we're replying to

spec/models/draft_spec.rb

@@ -3,37 +3,70 @@
 require 'rails_helper'
 
 describe Draft do
-  before do
-    @user = Fabricate(:user)
+
+  fab!(:user) do
+    Fabricate(:user)
   end
+
+  context 'backup_drafts_to_pm_length' do
+    it "correctly backs up drafts to a personal message" do
+      SiteSetting.backup_drafts_to_pm_length = 1
+
+      draft = {
+        reply: "this is a reply",
+        random_key: "random"
+      }
+
+      Draft.set(user, "new_private_message", 0, draft.to_json)
+      draft["reply"] = "test" * 100
+      Draft.set(user, "new_private_message", 77, draft.to_json)
+
+      draft_post = BackupDraftPost.find_by(user_id: user.id, key: "new_private_message").post
+
+      expect(draft_post.revisions.count).to eq(0)
+
+      freeze_time 10.minutes.from_now
+
+      # this should trigger a post revision as 10 minutes have passed
+      draft["reply"] = "hello"
+      Draft.set(user, "new_private_message", 77, draft.to_json)
+
+      draft_topic = BackupDraftTopic.find_by(user_id: user.id)
+      expect(draft_topic.topic.posts_count).to eq(2)
+
+      draft_post.reload
+      expect(draft_post.revisions.count).to eq(1)
+    end
+  end
+
   it "can get a draft by user" do
-    Draft.set(@user, "test", 0, "data")
-    expect(Draft.get(@user, "test", 0)).to eq "data"
+    Draft.set(user, "test", 0, "data")
+    expect(Draft.get(user, "test", 0)).to eq "data"
   end
 
   it "uses the user id and key correctly" do
-    Draft.set(@user, "test", 0, "data")
+    Draft.set(user, "test", 0, "data")
     expect(Draft.get(Fabricate.build(:coding_horror), "test", 0)).to eq nil
   end
 
   it "should overwrite draft data correctly" do
-    Draft.set(@user, "test", 0, "data")
-    Draft.set(@user, "test", 0, "new data")
-    expect(Draft.get(@user, "test", 0)).to eq "new data"
+    Draft.set(user, "test", 0, "data")
+    Draft.set(user, "test", 0, "new data")
+    expect(Draft.get(user, "test", 0)).to eq "new data"
   end
 
   it "should clear drafts on request" do
-    Draft.set(@user, "test", 0, "data")
-    Draft.clear(@user, "test", 0)
-    expect(Draft.get(@user, "test", 0)).to eq nil
+    Draft.set(user, "test", 0, "data")
+    Draft.clear(user, "test", 0)
+    expect(Draft.get(user, "test", 0)).to eq nil
   end
 
   it "should disregard old draft if sequence decreases" do
-    Draft.set(@user, "test", 0, "data")
-    Draft.set(@user, "test", 1, "hello")
-    Draft.set(@user, "test", 0, "foo")
-    expect(Draft.get(@user, "test", 0)).to eq nil
-    expect(Draft.get(@user, "test", 1)).to eq "hello"
+    Draft.set(user, "test", 0, "data")
+    Draft.set(user, "test", 1, "hello")
+    Draft.set(user, "test", 0, "foo")
+    expect(Draft.get(user, "test", 0)).to eq nil
+    expect(Draft.get(user, "test", 1)).to eq "hello"
   end
 
   it 'can cleanup old drafts' do
@@ -71,25 +104,25 @@ describe Draft do
     let(:public_topic) { public_post.topic }
 
     let(:stream) do
-      Draft.stream(user: @user)
+      Draft.stream(user: user)
     end
 
     it "should include the correct number of drafts in the stream" do
-      Draft.set(@user, "test", 0, '{"reply":"hey.","action":"createTopic","title":"Hey"}')
-      Draft.set(@user, "test2", 0, '{"reply":"howdy"}')
+      Draft.set(user, "test", 0, '{"reply":"hey.","action":"createTopic","title":"Hey"}')
+      Draft.set(user, "test2", 0, '{"reply":"howdy"}')
       expect(stream.count).to eq(2)
     end
 
     it "should include the right topic id in a draft reply in the stream" do
-      Draft.set(@user, "topic_#{public_topic.id}", 0, '{"reply":"hi"}')
+      Draft.set(user, "topic_#{public_topic.id}", 0, '{"reply":"hi"}')
       draft_row = stream.first
       expect(draft_row.topic_id).to eq(public_topic.id)
     end
 
     it "should include the right draft username in the stream" do
-      Draft.set(@user, "topic_#{public_topic.id}", 0, '{"reply":"hey"}')
+      Draft.set(user, "topic_#{public_topic.id}", 0, '{"reply":"hey"}')
       draft_row = stream.first
-      expect(draft_row.draft_username).to eq(@user.username)
+      expect(draft_row.draft_username).to eq(user.username)
     end
 
   end