Fix reply-by-email not working due to queue name mismatch

mail_room was configured to deliver mail to the `incoming_email`
queue while `EmailReceiveWorker` was reading the `email_receiver`
queue. Adds a migration that repeats the work of a previous
migration to ensure all mails that wound up in the old
queue get processed.

Closes #23689

2 files changed, 64 insertions, 1 deletions

diff --git a/db/migrate/20161024042317_migrate_mailroom_queue_from_default.rb b/db/migrate/20161024042317_migrate_mailroom_queue_from_default.rb
new file mode 100644
index 00000000000..06d07bdb835
--- /dev/null
+++ b/db/migrate/20161024042317_migrate_mailroom_queue_from_default.rb
@@ -0,0 +1,63 @@
+require 'json'
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class MigrateMailroomQueueFromDefault < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = true
+
+  DOWNTIME_REASON = <<-EOF
+  Moving Sidekiq jobs from queues requires Sidekiq to be stopped. Not stopping
+  Sidekiq will result in the loss of jobs that are scheduled after this
+  migration completes.
+  EOF
+
+  disable_ddl_transaction!
+
+  # Jobs for which the queue names have been changed (e.g. multiple workers
+  # using the same non-default queue).
+  #
+  # The keys are the old queue names, the values the jobs to move and their new
+  # queue names.
+  RENAMED_QUEUES = {
+      incoming_email: {
+          'EmailReceiverWorker' => :email_receiver
+      }
+  }
+
+  def up
+    Sidekiq.redis do |redis|
+      RENAMED_QUEUES.each do |queue, jobs|
+        migrate_from_queue(redis, queue, jobs)
+      end
+    end
+  end
+
+  def down
+    Sidekiq.redis do |redis|
+      RENAMED_QUEUES.each do |dest_queue, jobs|
+        jobs.each do |worker, from_queue|
+          migrate_from_queue(redis, from_queue, worker => dest_queue)
+        end
+      end
+    end
+  end
+
+  def migrate_from_queue(redis, queue, job_mapping)
+    while job = redis.lpop("queue:#{queue}")
+      payload = JSON.load(job)
+      new_queue = job_mapping[payload['class']]
+
+      # If we have no target queue to migrate to we're probably dealing with
+      # some ancient job for which the worker no longer exists. In that case
+      # there's no sane option we can take, other than just dropping the job.
+      next unless new_queue
+
+      payload['queue'] = new_queue
+
+      redis.lpush("queue:#{new_queue}", JSON.dump(payload))
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index f5c01511195..02282b0f666 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20161019213545) do
+ActiveRecord::Schema.define(version: 20161024042317) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"