Comment 1 for bug 1642234

There is very little information in this bug report, like what release of nova are you using? What's the env topology? There is obviously a mysql connection failure, so you should probably investigate the mysql deployment / config / logs as that's what nova is failing on:

2016-11-16 19:44:18.958 2762 ERROR nova.api.openstack.extensions raise err.OperationalError(2006, "MySQL server has gone away (%r)" % (e,))
2016-11-16 19:44:18.958 2762 ERROR nova.api.openstack.extensions OperationalError: (pymysql.err.OperationalError) (2006, "MySQL server has gone away (error(32, 'Broken pipe'))")