salt-minion starts up many subporcess

Description of Issue

I recieved a CPU overload alert, and find out that my minion server is running hundreds of salt-minion. They were started up by main process of salt-minion service at different time. And the subprocess still exist even i kill the main process.

I have no idea why it happeds. In other minion server, only one salt-minion process is found. How can I avoid it happends again ?

Setup

• /etc/salt/minon file has only one config, that is master:
• and this is systemd service unit configuration

  [Unit]
  Description=The Salt Minion
  Documentation=man:salt-minion(1) file:///usr/share/doc/salt/html/contents.html https://docs.saltstack.com/en/latest/contents.html
  After=network.target salt-master.service
  
  [Service]
  KillMode=process
  Type=notify
  NotifyAccess=all
  LimitNOFILE=8192
  ExecStart=/usr/bin/salt-minion
  
  [Install]
  WantedBy=multi-user.target
  

Steps to Reproduce Issue

• all PPIDs of subprocess is 1, and main process 5475 showed by systemctl status salt-minion is running too.
  
  
• afiter running kill -9 5475, the service became failed，but subprocess were still existing by using ps -ef
  

Versions Report

master is 2018.3.3, and minion is 2018.3.4

Salt Version:
           Salt: 2018.3.3
 
Dependency Versions:
           cffi: 1.12.3
       cherrypy: unknown
       dateutil: Not Installed
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
          ioflo: Not Installed
         Jinja2: 2.9.6
        libgit2: Not Installed
        libnacl: Not Installed
       M2Crypto: 0.21.1
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.5.6
   mysql-python: Not Installed
      pycparser: 2.19
       pycrypto: 2.6.1
   pycryptodome: Not Installed
         pygit2: Not Installed
         Python: 2.7.5 (default, Oct 30 2018, 23:45:53)
   python-gnupg: Not Installed
         PyYAML: 3.11
          PyZMQ: 15.3.0
           RAET: Not Installed
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.2.1
            ZMQ: 4.1.4
 
System Versions:
           dist: centos 7.4.1708 Core
         locale: UTF-8
        machine: x86_64
        release: 3.10.0-693.2.2.el7.x86_64
         system: Linux
        version: CentOS Linux 7.4.1708 Core

And salt-minion is version is 2018.3.4 (Oxygen)

Salt Version:
           Salt: 2018.3.4
 
Dependency Versions:
           cffi: Not Installed
       cherrypy: Not Installed
       dateutil: Not Installed
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
          ioflo: Not Installed
         Jinja2: 2.10
        libgit2: Not Installed
        libnacl: Not Installed
       M2Crypto: Not Installed
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.5.6
   mysql-python: Not Installed
      pycparser: Not Installed
       pycrypto: 2.6.1
   pycryptodome: Not Installed
         pygit2: Not Installed
         Python: 2.7.5 (default, Oct 30 2018, 23:45:53)
   python-gnupg: Not Installed
         PyYAML: 3.11
          PyZMQ: 15.3.0
           RAET: Not Installed
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.2.1
            ZMQ: 4.1.4
 
System Versions:
           dist: centos 7.6.1810 Core
         locale: UTF-8
        machine: x86_64
        release: 3.10.0-957.5.1.el7.x86_64
         system: Linux
        version: CentOS Linux 7.6.1810 Core

Start by reviewing the salt-minion systemd unit, especially KillMode=process, alongside the reported /etc/salt/minon configuration and the salt-minion service entry point. Reproduce the process-tree behavior with systemctl status salt-minion and ps -ef, then determine why subprocesses remain after the main process exits. Done means the cause is identified and the service no longer leaves unintended subprocesses behind.