FEATURE: Remap uploads during restore when S3 or CDN changes

In order for this to work the Backuper stores a couple of site settings
in the new backup_metadata table, because the old setting values might
not be available on restore anymore.

app/models/backup_metadata.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class BackupMetadata < ActiveRecord::Base
+  def self.value_for(name)
+    where(name: name).pluck(:value).first
+  end
+end
+
+# == Schema Information
+#
+# Table name: backup_metadata
+#
+#  id    :bigint           not null, primary key
+#  name  :string           not null
+#  value :string
+#

db/migrate/20190704133453_create_backup_metadata.rb

@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+class CreateBackupMetadata < ActiveRecord::Migration[5.2]
+  def change
+    create_table :backup_metadata do |t|
+      t.string :name, null: false
+      t.string :value
+    end
+  end
+end

lib/backup_restore/backuper.rb

@@ -32,6 +32,8 @@ module BackupRestore
       ensure_directory_exists(@tmp_directory)
       ensure_directory_exists(@archive_directory)
 
+      update_metadata
+
       ### READ-ONLY / START ###
       enable_readonly_mode
 
@@ -117,6 +119,16 @@ module BackupRestore
       BackupRestore.mark_as_running!
     end
 
+    def update_metadata
+      log "Updating metadata..."
+      BackupMetadata.delete_all
+      BackupMetadata.create!(name: "base_url", value: Discourse.base_url)
+      BackupMetadata.create!(name: "cdn_url", value: Discourse.asset_host)
+      BackupMetadata.create!(name: "s3_base_url", value: SiteSetting.Upload.enable_s3_uploads ? SiteSetting.Upload.s3_base_url : nil)
+      BackupMetadata.create!(name: "s3_cdn_url", value: SiteSetting.Upload.enable_s3_uploads ? SiteSetting.Upload.s3_cdn_url : nil)
+      BackupMetadata.create!(name: "db_name", value: RailsMultisite::ConnectionManagement.current_db)
+    end
+
     def enable_readonly_mode
       return if @readonly_mode_was_enabled
       log "Enabling readonly mode..."

lib/backup_restore/restorer.rb

@@ -434,7 +434,7 @@ module BackupRestore
           FileUtils.mkdir_p("uploads")
 
           tmp_uploads_path = Dir.glob(File.join(@tmp_directory, "uploads", "*")).first
-          previous_db_name = File.basename(tmp_uploads_path)
+          previous_db_name = BackupMetadata.value_for("db_name") || File.basename(tmp_uploads_path)
           current_db_name = RailsMultisite::ConnectionManagement.current_db
           optimized_images_exist = File.exist?(File.join(tmp_uploads_path, 'optimized'))
 
@@ -443,10 +443,7 @@ module BackupRestore
             failure_message: "Failed to restore uploads."
           )
 
-          if previous_db_name != current_db_name
-            log "Remapping uploads..."
-            DbHelper.remap("uploads/#{previous_db_name}", "uploads/#{current_db_name}")
-          end
+          remap_uploads(previous_db_name, current_db_name)
 
           if SiteSetting.Upload.enable_s3_uploads
             migrate_to_s3
@@ -458,6 +455,45 @@ module BackupRestore
       end
     end
 
+    def remap_uploads(previous_db_name, current_db_name)
+      log "Remapping uploads..."
+
+      if (old_base_url = BackupMetadata.value_for("base_url")) && old_base_url != Discourse.base_url
+        DbHelper.remap(old_base_url, Discourse.base_url)
+      end
+
+      current_s3_base_url = SiteSetting.Upload.enable_s3_uploads ? SiteSetting.Upload.s3_base_url : nil
+      if (old_s3_base_url = BackupMetadata.value_for("s3_base_url")) && old_base_url != current_s3_base_url
+        DbHelper.remap("#{old_s3_base_url}/", "/uploads/#{current_db_name}/")
+      end
+
+      current_s3_cdn_url = SiteSetting.Upload.enable_s3_uploads ? SiteSetting.Upload.s3_cdn_url : nil
+      if (old_s3_cdn_url = BackupMetadata.value_for("s3_cdn_url")) && old_s3_cdn_url != current_s3_cdn_url
+        base_url = SiteSetting.Upload.enable_s3_uploads ? SiteSetting.Upload.s3_cdn_url : Discourse.base_url
+        DbHelper.remap("#{old_s3_cdn_url}/", UrlHelper.schemaless("#{base_url}/uploads/#{current_db_name}/"))
+
+        old_host = URI.parse(old_s3_cdn_url).host
+        new_host = URI.parse(base_url.presence || Discourse.base_url).host
+        DbHelper.remap(old_host, new_host)
+      end
+
+      if (old_cdn_url = BackupMetadata.value_for("cdn_url")) && old_cdn_url != Discourse.asset_host
+        base_url = SiteSetting.Upload.enable_s3_uploads ? SiteSetting.Upload.s3_base_url : Discourse.base_url
+        DbHelper.remap("#{old_cdn_url}/", UrlHelper.schemaless("#{base_url}/"))
+
+        old_host = URI.parse(old_cdn_url).host
+        new_host = URI.parse(base_url.presence || Discourse.base_url).host
+        DbHelper.remap(old_host, new_host)
+      end
+
+      if previous_db_name != current_db_name
+        DbHelper.remap("uploads/#{previous_db_name}", "uploads/#{current_db_name}")
+      end
+
+    rescue => ex
+      log "Something went wrong while remapping uploads.", ex
+    end
+
     def migrate_to_s3
       log "Migrating uploads to S3..."
       ENV["SKIP_FAILED"] = "1"
@@ -589,5 +625,4 @@ module BackupRestore
     end
 
   end
-
 end