Comment 1 for bug 1642509

keystone endpoint-list was being stuck because of mysql. mysql was stuck for some reason. on killing mysql and starting it back, system recovered. many of other mysql commands were stuck as well.

root@nodec10:/var/log/mysql# ps ax| grep mysql
  609 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
 5059 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
 8319 ? S 0:00 /bin/sh /usr/bin/mysqld_safe
 9683 ? Sl 67:41 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib/mysql/plugin --user=mysql --log-error=/var/log/mysql/error.log --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/run/mysqld/mysqld.sock --port=3306 --wsrep_start_position=00000000-0000-0000-0000-000000000000:-1
14121 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
15248 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
26339 pts/16 S+ 0:00 grep --color=auto mysql
26677 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
27280 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
27396 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
28155 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
28204 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
28501 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
28681 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
28942 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
29165 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
29380 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
30772 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
31788 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;
32297 ? S 0:00 mysql -ucmon -px xx -hlocalhost -P3306 -e use cmon; truncate table cmon_log;

keystone-all.log reported following errors:
2016-11-17 11:46:05.224 30182 WARNING oslo_db.sqlalchemy.engines [req-898fff2f-fc93-42ce-a707-5dfcd8935aa7 - - - - -] SQL connection failed. -14 attempts left.
2016-11-17 11:46:06.231 30179 WARNING oslo_db.sqlalchemy.engines [req-f386c607-f517-4a83-83eb-281f984527b2 - - - - -] SQL connection failed. -14 attempts left.
2016-11-17 11:46:08.245 30181 WARNING oslo_db.sqlalchemy.engines [req-f66b6d86-872c-4bcd-9506-afea2aaf7a49 - - - - -] SQL connection failed. -15 attempts left.
2016-11-17 11:46:08.246 30180 WARNING oslo_db.sqlalchemy.engines [req-cb3a0244-836e-4490-ada0-4dd7edaba110 - - - - -] SQL connection failed. -15 attempts left.
2016-11-17 11:46:09.688 30183 WARNING oslo_db.sqlalchemy.engines [req-67023e89-6033-4bbc-a7e7-eb658fbadd13 - - - - -] SQL connection failed. -15 attempts left.
2016-11-17 11:46:10.225 30182 WARNING oslo_db.sqlalchemy.engines [req-898fff2f-fc93-42ce-a707-5dfcd8935aa7 - - - - -] SQL connection failed. -15 attempts left.
2016-11-17 11:46:11.233 30179 WARNING oslo_db.sqlalchemy.engines [req-f386c607-f517-4a83-83eb-281f984527b2 - - - - -] SQL connection failed. -15 attempts left.
2016-11-17 11:46:13.249 30181 WARNING oslo_db.sqlalchemy.engines [req-f66b6d86-872c-4bcd-9506-afea2aaf7a49 - - - - -] SQL connection failed. -16 attempts left.
2016-11-17 11:46:13.251 30180 WARNING oslo_db.sqlalchemy.engines [req-cb3a0244-836e-4490-ada0-4dd7edaba110 - - - - -] SQL connection failed. -16 attempts left.
2016-11-17 11:46:14.691 30183 WARNING oslo_db.sqlalchemy.engines [req-67023e89-6033-4bbc-a7e7-eb658fbadd13 - - - - -] SQL connection failed. -16 attempts left.
2016-11-17 11:46:15.230 30182 WARNING oslo_db.sqlalchemy.engines [req-898fff2f-fc93-42ce-a707-5dfcd8935aa7 - - - - -] SQL connection failed. -16 attempts left.
2016-11-17 11:46:16.237 30179 WARNING oslo_db.sqlalchemy.engines [req-f386c607-f517-4a83-83eb-281f984527b2 - - - - -] SQL connection failed. -16 attempts left.