Deploy apps with docker swarm
I received alert email that my website crushed down, after checking, I found mysql container is stoped..
I checked system log, found infos as below:
Jan 22 18:42:39 ip-172-31-28-84 kernel: Out of memory: Kill process 597 (mysqld) score 226 or sacrifice child
Jan 22 18:42:39 ip-172-31-28-84 kernel: Killed process 597 (mysqld) total-vm:1128616kB, anon-rss:228980kB, file-rss:0kB, shmem-rss:0kB
I think the process is killed by kernel for lack of memory, because the server only has 1GB memory ..
[root@ip-172-31-28-84 log]# free -h
total used free shared buff/cache available
Mem: 990M 559M 83M 113M 348M 133M
Swap: 0B 0B 0B
I restarted mysql container, and check containers’s status:
[root@ip-172-31-28-84 log]# docker stats --no-stream
CONTAINER CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS
9e5a47485105 0.00% 28.66MiB / 990.8MiB 2.89% 90.9MB / 43.2MB 24.9MB / 0B 2
c9187825cc0c 0.00% 273.8MiB / 990.8MiB 27.63% 3.95GB / 1.02GB 11GB / 2.58MB 11
628e301d00a1 0.04% 217.9MiB / 990.8MiB 21.99% 10.4MB / 136MB 101MB / 363MB 31
there is no limitation on resources, so mysql will occupy more memory which caused being killed.
After thinking about this, I decided deploy by docker swarm which will start container if stoped, and also could restrict resources for every container.
1.init docker swarm on single server
docker swarm init
2.modify blog-compose.yml to support swarm, please follow gist
https://gist.githubusercontent.com/hongmengwang/c5ca0368f5de15a612972c4bb676d409/raw/d8d706bb42769f20506d00f01603f34686b4fac9/blog-compose.yml
3.deploy service
docker stack deploy -c blog-compose.yml blog
4.check container status
[root@ip-172-31-28-84 docker]# docker stack services blog
ID NAME MODE REPLICAS IMAGE PORTS
0l68syg6q1bi blog_nginx replicated 1/1 nginx:1.13.8 *:80->80/tcp,*:443->443/tcp
cx82xalbzdzu blog_wordpress replicated 1/1 wordpress:4.9.1
xulj5sbkbapb blog_mysql replicated 1/1 mysql:5.7
5.check container stats
[root@ip-172-31-28-84 docker]# docker stats --no-stream
CONTAINER CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS
08bc88c00f0c 0.04% 189.7MiB / 250MiB 75.86% 70.5kB / 1.02MB 14MB / 13.9MB 30
64d37b150392 0.00% 29.02MiB / 50MiB 58.05% 12.6kB / 14.7kB 1.24MB / 0B 2
f33ecf2c045e 0.00% 92.32MiB / 300MiB 30.77% 1.03MB / 76.8kB 27.8MB / 0B 9
The memory of each container is restricted, it will not occupy more memory than limitation, I will keep on watching to see if works well.
Wang's Tech Blog 
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