Sign inSign up

xr09/flare

By xr09

•Updated 16 days ago

Debug how containers react to signals

Image
0

2.7K

xr09/flare repository overview

⁠Flare

Flare is a tool to debug how containers are reacting to signals.

⁠Source code

https://github.com/xr09/flare⁠

⁠Why use Flare

The idea is to be able to determine if SIGTERM signals are reaching the processes inside containers for them to be able to terminate gracefully⁠.

After running this image the flare process will print its PID and wait for signals.

Signals captured:

  • SIGUSR1: will print to stdout
  • SIGINT: will print to stdout and exit the program (keyboard interruption)
  • SIGTERM: will print to stdout and exit the program
⁠Usage

Flare takes 1 positional parameter called sleep_time, this will be the amount of time the program will take to close its unfinished business when receiving a TERM signal, emulating this way a real world workload.

❯ ./flare 5
Flare running with PID 91082

received SIGTERM
the program will take 5s to finish correctly
...
SUCCESS: the program had enough time to finish
⁠Flare on Docker

Pass the desired sleep time as the CMD.

$ docker run --rm -ti --name flare xr09/flare 5
Flare running with PID 1

received SIGUSR1
received SIGUSR1
received SIGUSR1
received SIGTERM
the program will take 5s to finish correctly
...
SUCCESS: the program had enough time to finish

Send USR1 with docker kill -s USR1 flare

Send TERM with docker stop flare or docker kill -s TERM flare

After receiving a SIGTERM it will print it then wait 5 seconds and shutdown.

⁠Flare on Kubernetes

This tools is convenient for debugging cases where terminationGracePeriodSeconds is needed on Kubernetes.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: flare
  labels:
    app: flare
spec:
  replicas: 3
  selector:
    matchLabels:
      app: flare
  template:
    metadata:
      labels:
        app: flare
    spec:
      terminationGracePeriodSeconds: 60
      containers:
      - name: flare
        image: xr09/flare
        args: ["45"]

Proceed to delete one of the pods:

❯ kubectl get po
NAME                     READY   STATUS    RESTARTS   AGE
flare-777c45d94c-75lmx   1/1     Running   0          11s
flare-777c45d94c-w6kxm   1/1     Running   0          11s
flare-777c45d94c-xxsdn   1/1     Running   0          11s

❯ kubectl delete pod flare-777c45d94c-xxsdn
pod "flare-777c45d94c-xxsdn" deleted

It should have enough time to close by itself:

❯ kubectl logs -f flare-777c45d94c-xxsdn
Flare running with PID 1

received SIGTERM
the program will take 45s to finish correctly
...
SUCCESS: the program had enough time to finish

Tag summary

Content type

Image

Digest

sha256:f72689faf…

Size

10.1 MB

Last updated

16 days ago

docker pull xr09/flare