Implementation

• concurrency status save to etcd. In case a server is down it loses concurrency control
• server start some goroutine and assign a job status to a fixed one of the gorountine maintenance
• modify grpc service job.GetJob and job.ExecDone, add the token's distribution and recycle logic
• when an agent make a job.GetJob rpc call, server reduce concurrency first. if succeed return job obj, if not sleep a well and retry, until this is succeed.

from djob.