Killing subprocess from inside a Docker container kills the entire container - linux

On my Windows machine, I started a Docker container from docker compose. My entrypoint is a Go filewatcher that runs a task of a taskmanager on every filechange. The executed task builds and runs the Go program.
But before I can build and run the program again after filechanges I have to kill the previous running version. But every time I kill the app process, the container is also gone.
The goal is to kill only the svc1 process with PID 74 in this example. I tried pkill -9 svc1 and kill $(pgrep svc1). But every time the parent processes are killed too.
The commandline output from inside the container:
root#bf073c39e6a2:/app/cmd/svc1# ps -aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 2.5 0.0 104812 2940 ? Ssl 13:38 0:00 /go/bin/watcher
root 13 0.0 0.0 294316 7576 ? Sl 13:38 0:00 /go/bin/task de
root 74 0.0 0.0 219284 4908 ? Sl 13:38 0:00 /svc1
root 82 0.2 0.0 18184 3160 pts/0 Ss 13:38 0:00 /bin/bash
root 87 0.0 0.0 36632 2824 pts/0 R+ 13:38 0:00 ps -aux
root#bf073c39e6a2:/app/cmd/svc1# ps -afx
PID TTY STAT TIME COMMAND
82 pts/0 Ss 0:00 /bin/bash
88 pts/0 R+ 0:00 \_ ps -afx
1 ? Ssl 0:01 /go/bin/watcher -cmd /go/bin/task dev -startcmd
13 ? Sl 0:00 /go/bin/task dev
74 ? Sl 0:00 \_ /svc1
root#bf073c39e6a2:/app/cmd/svc1# pkill -9 svc1
root#bf073c39e6a2:/app/cmd/svc1
Switching to the containerlog:
task: Failed to run task "dev": exit status 255
2019/08/16 14:20:21 exit status 1
"dev" is the name of the task in the taskmanger.
The Dockerfile:
FROM golang:stretch
RUN go get -u -v github.com/radovskyb/watcher/... \
&& go get -u -v github.com/go-task/task/cmd/task
WORKDIR /app
COPY ./Taskfile.yml ./Taskfile.yml
ENTRYPOINT ["/go/bin/watcher", "-cmd", "/go/bin/task dev", "-startcmd"]
I expect only the process with the target PID is killed and not the parent process that spawned it it.

You can use process manager like "supervisord" and configure it to re-execute your script or the command even if you killed it's process which will keep your container up and running.

Related

child_process didn't receive SIGTERM inside docker container

I'm writing test for electron application in typescript.
Inside application there are register listener for SIGTERM
process.on('SIGTERM', async () => {
console.log('before exit');
await this.exit(); //some inner function can't reach this statement anyway
});
Locally everything fine, but on CI when app running inside docker container looks like it didn't receive SIGTERM.
For starting application I'm using child_process.spawn
import type { ChildProcess } from 'child_process';
let yarnStart: ChildProcess = spawn('yarn', 'start', { shell: true });
// 'start' is just script in package.json
I try to kill application three different way and none of them works. Application didn't receive SIGTERM no before exit and after manually stopping ci-build in final-step ps aux showing my process.
// 1-way
yarnStart.kill('SIGTERM');
// 2-way
process.kill(yarnStart.pid, 'SIGTERM');
// 3-way
import { execSync } from 'child_process';
execSync(`kill -15 ${yarnStart.pid}`);
Why nodejs can't properly send SIGTERM inside docker container?
Only difference - locally I have debian-9(stretch) and image based on debian-10(buster). Same nodejs version 12.14.1. I will try to build container with stretch to see how it will behave, but skeptical about that this will help.
UPD
There is kind of difference in processes initiation(due to running scripts on CI in container, any instruction runs with /bin/sh -c)
when you execute ps aux you will see
//locally
myuser 101457 1.3 0.1 883544 58968 pts/8 Sl+ 10:32 0:00 /usr/bin/node /usr/share/yarn/bin/yarn.js start
myuser 101468 1.6 0.2 829316 69456 pts/8 Sl+ 10:32 0:00 /usr/bin/node /usr/share/yarn/lib/cli.js start
myuser 101479 1.6 0.2 829576 69296 pts/8 Sl+ 10:32 0:00 /usr/bin/node /usr/share/yarn/lib/cli.js start:debug
myuser 101490 0.2 0.0 564292 31140 pts/8 Sl+ 10:32 0:00 /usr/bin/node /home/myuser/myrepo/electron-app/node_modules/.bin/electron -r ts-node/register ./src/main.ts
myuser 101497 143 1.4 9215596 485132 pts/8 Sl+ 10:32 0:35 /home/myuser/myrepo/node_modules/electron/dist/electron -r ts-node/register ./src/main.ts
//container
root 495 0.0 0.0 2392 776 ? S 09:05 0:00 /bin/sh -c yarn start
root 496 1.0 0.2 893240 74336 ? Sl 09:05 0:00 /usr/local/bin/node /opt/yarn-v1.22.5/bin/yarn.js start
root 507 1.7 0.2 885588 68652 ? Sl 09:05 0:00 /usr/local/bin/node /opt/yarn-v1.22.5/lib/cli.js start
root 518 0.0 0.0 2396 712 ? S 09:05 0:00 /bin/sh -c yarn start:debug
root 519 1.7 0.2 885336 68608 ? Sl 09:05 0:00 /usr/local/bin/node /opt/yarn-v1.22.5/lib/cli.js start:debug
root 530 0.0 0.0 2396 780 ? S 09:05 0:00 /bin/sh -c electron -r ts-node/register ./src/main.ts
root 531 0.3 0.0 554764 32080 ? Sl 09:05 0:00 /usr/local/bin/node /opt/ci/jobfolder/job_id_423/electron-app/node_modules/.bin/electron -r ts-node/register ./src/main.ts
root 538 140 1.5 9072388 520824 ? Sl 09:05 0:26 /opt/ci/jobfolder/job_id_423/node_modules/electron/dist/electron -r ts-node/register ./src/main.ts
And actually killing process with
// 1-way
yarnStart.kill('SIGTERM');
works but it kills only /bin/sh -c yarn start and his child_process /usr/local/bin/node /opt/yarn-v1.22.5/bin/yarn.js start that actually spawn application still hanging
/bin/sh -c which comes with a load of problems, one of them notably that you’ll never see a signal in your application. And descendant processes create they own /bin/sh -c
I find a solution in https://stackoverflow.com/a/33556110/4577788
Also find alternative solution(but it didn't work for me, maybe becaus of specifics of nodejs execution).
You can kill all the processes belonging to the same process tree using the Process Group ID. More datailed info can be found here https://stackoverflow.com/a/15139734/4577788
When I try to execute execSync('kill -- -942'); or execSync('kill -- "-942"');
Error occure kill: illegal number -, didn't find why it occure and hove to fix it.

How does 'kill -STOP and kill -CONT' work?

I'm facing an issue.
We have a clean script using to clean old files, and sometimes we need stop it for and will start it again later. Like the below processes. We use kill -STOP $pid and kill -CONT $pid in check.sh to control the clean.sh, $pid is all the pids of clean.sh (at there, they are 23939, 25804):
root 4321 0.0 0.0 74876 1184 ? Ss 2015 0:25 crond
root 23547 0.0 0.0 102084 1604 ? S 2015 0:00 \_ crond
root 23571 0.0 0.0 8728 972 ? Ss 2015 0:00 \_ /bin/bash -c bash /home/test/sbin/check.sh >>/home/test/log/check.log 2>&1
root 23577 0.0 0.0 8732 1092 ? S 2015 0:00 \_ bash /home/test/sbin/check.sh
root 23939 0.0 0.0 8860 1192 ? S 2015 0:45 \_ bash /home/test/bin/clean.sh 30
root 25804 0.0 0.0 8860 620 ? S 2015 0:00 \_ bash /home/test/bin/clean.sh 30
root 25805 0.0 0.0 14432 284 ? T 2015 0:00 \_ ls -d ./455bb4cba6142427156d2b959b8b0986/120x60/ ./455bb4cba6142427156d2b959b8b0986/80x
root 25808 0.0 0.0 3816 432 ? S 2015 0:00 \_ wc -l
Once the check.sh stopped clean.sh, hours later, check.sh started clean.sh, but there is a strange thing, after a stop and continue, there is a child process 'ls -d ....', it's still stopping.
Could you tell me if it's caused by wrong use of the signal? And how can I modify it?
ok, same like my description is not clear, my bad English...
Not sure what's the reason, but there is a way to sovle it:
kill -CONT $pid
pkill -CONT -P $pid
This will continue the child process.

Can't stop/restart Apache2 service

Trying to stop Apache2 service, but get PID error:
#service apache2 stop
[FAIL] Stopping web server: apache2 failed!
[....] There are processes named 'apache2' running which do not match your pid file which are left untouched in the name of safety, Plea[warnview the situation by hand. ... (warning).
Trying to kill, those processes:
#kill -9 $(ps aux | grep apache2 | awk '{print $2}')
but they get re-spawned again:
#ps aux | grep apache2
root 19279 0.0 0.0 4080 348 ? Ss 05:10 0:00 runsv apache2
root 19280 0.0 0.0 4316 648 ? S 05:10 0:00 /bin/sh /usr/sbin/apache2ctl -D FOREGROUND
root 19282 0.0 0.0 91344 5424 ? S 05:10 0:00 /usr/sbin/apache2 -D FOREGROUND
www-data 19284 0.0 0.0 380500 2812 ? Sl 05:10 0:00 /usr/sbin/apache2 -D FOREGROUND
www-data 19285 0.0 0.0 380500 2812 ? Sl 05:10 0:00 /usr/sbin/apache2 -D FOREGROUND
And though the processes are running i can't connect to the server on port 80. /var/log/apache2/error.log.1 has no new messages when i do the kill -9.
Before I tried to restart everything worked perfectly.
Running on Debian: Linux adara 3.2.0-4-amd64 #1 SMP Debian 3.2.54-2 x86_64 GNU/Linux
UPD:
also tried apache2ctl:
#/usr/sbin/apache2ctl -k stop
AH00526: Syntax error on line 76 of /etc/apache2/apache2.conf:
PidFile takes one argument, A file for logging the server process ID
Action '-k stop' failed.
The Apache error log may have more information.
but there is no pid file in /var/run/apache2
I'm new to linux, looks like it has to do something with startup scripts, but can't figure out what exactly.
Below is the command to find out the process running on port 80
lsof -i tcp:80
Kill the process with PID.Restart the system once to check if their is any start up script executing and using the Port 80 which is preventing you to start your service.
For start up scripts you can check
/etc/init.d/ or /etc/rc.local or crontab - e
You can try Apache official documentation for stop/restart operations.
link

in linux - show a list of all processes and note if they are running or suspended

I'm new to linux.
How can I show a list of all processes that says about each process if it's running or suspended?
I've tried
ps -ef|grep myusername
but it doesn't say if the processes are running or not.
also tried
ps ux
same thing, it doesn't say if the processes are running or not.
I'm looking for something like this list:
I get this list when I move a process to background, I don't know how to see it otherwise...
You can use "ps" to list processes, This (ps aux) will list all the processes. Given an example output of it below.
ps aux | more
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.1 189160 9376 ? Ss 15:51 0:04 /usr/lib/systemd/systemd --switched-root --system --deserialize 20
root 2 0.0 0.0 0 0 ? S 15:51 0:00 [kthreadd]
root 3 0.0 0.0 0 0 ? S 15:51 0:00 [ksoftirqd/0]
root 5 0.0 0.0 0 0 ? S< 15:51 0:00 [kworker/0:0H]
root 7 0.0 0.0 0 0 ? S 15:51 0:06 [rcu_sched]
root 8 0.0 0.0 0 0 ? S 15:51 0:00 [rcu_bh]
root 9 0.0 0.0 0 0 ? S 15:51 0:04 [rcuos/0]
By checking the STAT of the process ( UNDER "STAT" ) you can identify the process states, Below are some possible states codes.
R running or runnable (on run queue)
D uninterruptible sleep (usually IO)
S interruptible sleep (waiting for an event to complete)
Z defunct/zombie, terminated but not reaped by its parent
T stopped, either by a job control signal or because it is being
traced
You can type "man ps" to get more info.
You can use htop to see the list of processes and there is a column for process state
What does a C process status mean in htop?
http://www.howtogeek.com/howto/ubuntu/using-htop-to-monitor-system-processes-on-linux/
ps -p PID -o comm=
Enter the code above where PID is PID of the process.
Following command will be more helpful to you.
Use the command : sudo lsof -i -n -P
This command lists the Application Name, PID, User, IP version, Device ID and the Node with Port Name. It shows both TCP and UDP.
Variations :
To format it in a nice, readable way; use :
sudo lsof -i -n -P | more
To view view only TCP connections :
sudo lsof -i -n -P | grep TCP | more
To view view only UDP connections :
sudo lsof -i -n -P | grep UDP | more

How to see a terminal output from a previously closed terminal

I connect to a remote server using SSH
I was compiling using cmake and then make, it's not common to have a progress percentage in compilation process, but this time it has. I was watching the compilation process until my internet connection failed, so puTTY closed the session and I had to connect again to my server. I though that all the progress was lost, but i first make sure by watching the processes list by ps aux command, and I noticed that the processes related to the compilation are still running:
1160 tty1 Ss+ 0:00 /sbin/mingetty tty1
2265 ? Ss 0:00 sshd: root#pts/1
2269 pts/1 Ss 0:00 -bash
2353 pts/1 S+ 0:00 make
2356 pts/1 S+ 0:00 make -f CMakeFiles/Makefile2 all
2952 ? S 0:00 pickup -l -t fifo -u
3085 ? Ss 0:00 sshd: root#pts/0
3089 pts/0 Ss 0:00 -bash
3500 pts/1 S+ 0:01 make -f src/compiler/CMakeFiles/hphp_analysis.dir/bui
3509 pts/1 S+ 0:00 /bin/sh -c cd /root/hiphop/hiphop-php/src/compiler &&
3510 pts/1 S+ 0:00 /usr/bin/g++44 -DNO_JEMALLOC=1 -DNO_TCMALLOC=1 -D_GNU
3511 pts/1 R+ 0:03 /usr/libexec/gcc/x86_64-redhat-linux6E/4.4.4/cc1plus
3512 pts/0 R+ 0:00 ps ax
I would like to know if is possible to watch the current progress of the compilation by watching the previously closed terminal output. Something similar like 'cat /dev/vcsa1' or something
As per the comment above, you should have used screen.
As it is, you could try to peek at the file descriptors used by sshd and the shell that you started, but I don't think this will get you very far.

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