20190521更新
root@servicecloud:/usr/local/docker/runner# docker exec -it gitlab-runner gitlab-runner register
Running in system-mode.
Please enter the gitlab-ci coordinator URL (e.g. https://gitlab.com/):
http://192.168.1.21/
Please enter the gitlab-ci token for this runner:
p553g3xwJENmY9ENm26i
Please enter the gitlab-ci description for this runner:
[c50b716e6ddc]:
Please enter the gitlab-ci tags for this runner (comma separated):
deploy
Registering runner... succeeded runner=p553g3xw
Please enter the executor: ssh, docker+machine, docker, docker-ssh, parallels, shell, virtualbox, docker-ssh+machine, kubernetes:
shell
Runner registered successfully. Feel free to start it, but if it's running already the config should be automatically reloaded!
如上所示，由于在配置runner时，选择了deploy的tags，而在gitlab后台默认是不允许没有任何标签的作业，我上传任务时没有打tags，所以被阻塞，勾选这个即可。
在Docker部署GitLab后，使用持续集成提交到GitLab开始几次正常通过测试，后来发现每次都是任务排队，重启Docker也不行，后来想到gitlab是和gitlab-runner是分在两个容器中的（为了GitLab压力考虑，gitlab-runner耗性能），在runner容器里执行
gitlab-ci-multi-runner restart
进行重启runner操作，刷新GitLab页面，就会发现自动执行runner任务了
终于找到原因了，是runner服务down掉了
