Sidekiq crashes with sd_markdown_render error when under high load

Sidekiq crashes almost daily with this error:

2017-08-17T16:26:58.515Z 4084 TID-ox1fzyws8 ActionMailer::DeliveryJob JID-f2593e2cebd93caba716c59c INFO: done: 5.978 sec
itlab [23 of 25 busy]: markdown.c:2897: sd_markdown_render: Assertion `md->work_bufs[0].size == 0' failed.

It would appear this occurs when sidekiq is under a fairly high load, with Sidekiq hitting 20+. Restarting gitlab resolves the issue until the next time. Note that after restarting Gitlab Sidekiq caps out at 25 until the queue is empty again.

Expand for output related to GitLab environment info

System information
System:		Ubuntu 14.04
Current User:	git
Using RVM:	no
Ruby Version:	2.3.3p222
Gem Version:	2.5.2
Bundler Version:1.15.3
Rake Version:	10.5.0
Redis Version:	2.8.4
Git Version:	2.7.3
Sidekiq Version:5.0.0
Go Version:	go1.8.3 linux/amd64
GitLab information
Version:	9.4.4
Revision:	2c79d92
Directory:	/home/git/gitlab
DB Adapter:	postgresql
URL:		https://gitlab.domain.com
HTTP Clone URL:	https://gitlab.domain.com/some-group/some-project.git
SSH Clone URL:	git@gitlab.domain.com:some-group/some-project.git
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers: khronos
GitLab Shell
Version:	5.3.1
Repository storage paths:

• default: /home/git/repositories Hooks: /home/git/gitlab-shell/hooks Git: /usr/local/bin/git

Possible fixes

This error is possibly related to redcarpet and these issues: https://github.com/vmg/redcarpet/issues/570 https://github.com/vmg/redcarpet/issues/176