why containerd service forks multiple child processes in its startup

[chathu-git]

Hi All,

I'm newbie to containerized applications and environment and during the learning I have noticed that when starting containerd service via systemctl there are multiple child processes can be seen ( checked via pstree ) . In my environment only containerd and docker were installed but no any containers started or deployed. version used - 1.4.3

What is the reason for spawn these child processes

Regards

[dmcgowan]

@chathu-git can you provide more information about the command you are running and the output you find questionable. There shouldn't be any child processes on startup. When running pstree I do see it reporting the child threads, but not any child processes.

[chathu-git]

Hi,

@dmcgowan I have just started service ( systemctl start containerd ) and when executed pstree -p below like output is shown.

[root@masternode stracelogs]# pstree -p
systemd(1)─┬─agetty(672)
├─auditd(632)───{auditd}(633)
├─chronyd(674)
├─containerd(11074)─┬─{containerd}(11075)
│ ├─{containerd}(11076)
│ ├─{containerd}(11077)
│ ├─{containerd}(11078)
│ ├─{containerd}(11079)
│ ├─{containerd}(11080)
│ ├─{containerd}(11081)
│ ├─{containerd}(11083)
│ ├─{containerd}(11084)
│ └─{containerd}(11085)
├─crond(666)
├─dbus-daemon(655)───{dbus-daemon}(656)
├─firewalld(688)───{firewalld}(916)

Also in a strace output log below like syscalls can been seen.

11074 clone(child_stack=0x7fbf975a2fb0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7fbf975a39d0, tls=0x7fbf975a3700, child_tidptr=0x7fbf975a39d0) = 11075

Regards

[chathu-git]

[dqminh]

@chathu-git these are threads managed by go runtime, if you use pstree -T (i.e. hide threads), the threads should disappear.

[chathu-git]

@dqminh @dmcgowan many thanks for the provided facts. Cheers !!!