restart fetch process only when it is idling

[FuhuXia]

Currently fetch process restart every 30 mins. We are not sure the consequences of the force restart, it might cause issue during harvesting such as this solr duplicate issue. We can do the restart process the same way as gather process, only restarting it when it is idling.

Sketch

[Notes or a checklist reflecting our understanding of the selected approach]

[FuhuXia]

This is broken. the script gives error. As a result, fetch and gather process may be interrupted by the restart task.