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，由於在配置runner時，選擇了deploy的tags，而在gitlab后台默認是不允許沒有任何標簽的作業，我上傳任務時沒有打tags，所以被阻塞，勾選這個即可。
在Docker部署GitLab后，使用持續集成提交到GitLab開始幾次正常通過測試，后來發現每次都是任務排隊，重啟Docker也不行，后來想到gitlab是和gitlab-runner是分在兩個容器中的（為了GitLab壓力考慮，gitlab-runner耗性能），在runner容器里執行
gitlab-ci-multi-runner restart
進行重啟runner操作，刷新GitLab頁面，就會發現自動執行runner任務了
終於找到原因了，是runner服務down掉了
