Lxc list struck after upgrading to lxd 4.0

$ ps fauxww | grep lxd
zhijli   11781  0.0  0.0  16988   988 pts/1    S+   23:21   0:00      \_ grep --colour=auto lxd
root     11049  0.1  0.1 1395052 36792 ?       Ssl  22:55   0:01 /usr/sbin/lxd --group lxd --logfile /var/log/lxd/lxd.log

$ sudo tail -f /var/log/lxd/lxd.log
t=2020-05-17T23:21:51+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=5" 
t=2020-05-17T23:21:52+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=6" 
t=2020-05-17T23:21:53+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=7" 
t=2020-05-17T23:21:54+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=8" 
t=2020-05-17T23:21:55+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=9" 
t=2020-05-17T23:21:56+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=10" 
t=2020-05-17T23:21:57+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=11" 
t=2020-05-17T23:22:00+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=0" 
t=2020-05-17T23:22:01+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=1" 
t=2020-05-17T23:22:01+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=2" 
t=2020-05-17T23:22:02+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=3" 
t=2020-05-17T23:22:03+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=4" 
t=2020-05-17T23:22:04+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=5" 
t=2020-05-17T23:22:05+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=6" 
t=2020-05-17T23:22:06+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=7" 
t=2020-05-17T23:22:07+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=8" 
t=2020-05-17T23:22:08+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=9" 
t=2020-05-17T23:22:09+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=10" 
t=2020-05-17T23:22:10+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=11" 
t=2020-05-17T23:22:13+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=0" 
t=2020-05-17T23:22:13+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=1" 
t=2020-05-17T23:22:13+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=2" 
t=2020-05-17T23:22:14+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=3" 
t=2020-05-17T23:22:15+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=4" 
t=2020-05-17T23:22:16+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=5" 
t=2020-05-17T23:22:17+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=6" 
t=2020-05-17T23:22:18+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=7" 
t=2020-05-17T23:22:19+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=8" 
t=2020-05-17T23:22:20+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=9" 
t=2020-05-17T23:22:21+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=10" 
t=2020-05-17T23:22:22+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=11" 
t=2020-05-17T23:22:25+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=0" 
t=2020-05-17T23:22:25+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=1" 
t=2020-05-17T23:22:26+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=2" 
t=2020-05-17T23:22:27+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=3" 
t=2020-05-17T23:22:28+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=4" 
t=2020-05-17T23:22:29+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=5" 
t=2020-05-17T23:22:30+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=6" 
t=2020-05-17T23:22:31+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=7" 
t=2020-05-17T23:22:32+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=8" 
t=2020-05-17T23:22:33+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=9" 
t=2020-05-17T23:22:34+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=10" 
t=2020-05-17T23:22:35+0800 lvl=warn msg="Dqlite: no known leader address=1 attempt=11" 
t=2020-05-17T23:22:36+0800 lvl=warn msg="Failed connecting to global database (attempt 130): failed to create dqlite connection: no available dqlite leader server found"

I fixed by myself:

mv /var/lib/lxd/database /var/lib/lxd/database.bak

/etc/init.d/lxd restart

@freeekanayaka