Running a command on all kubernetes pods of a service - kubernetes

Question

Hey I'm running a kubernetes cluster and I want to run a command on all pods that belong to a specific service.
As far as I know kubectl exec can only run on a pod and tracking all my pods is a ridiculous amount of work (which is one of the benefits of services).
Is there any way or tool that gives you the ability to "broadcast" to all pods in a service?
Thanks in advance for your help!

Answer 1

Here's a simple example with kubectl pipe to xargs, printing env of each pod:
k get pod \
-l {your label selectors} \
--field-selector=status.phase=Running \
-o custom-columns=name:metadata.name --no-headers \
| xargs -I{} kubectl exec {} env

Answer 2

As Bal Chua wrote, kubectl has no way to do this, but you can use bash script to do this:
#!/usr/bin/env bash
PROGNAME=$(basename $0)
function usage {
echo "usage: $PROGNAME [-n NAMESPACE] [-m MAX-PODS] -s SERVICE -- COMMAND"
echo " -s SERVICE K8s service, i.e. a pod selector (required)"
echo " COMMAND Command to execute on the pods"
echo " -n NAMESPACE K8s namespace (optional)"
echo " -m MAX-PODS Max number of pods to run on (optional; default=all)"
echo " -q Quiet mode"
echo " -d Dry run (don't actually exec)"
}
function header {
if [ -z $QUIET ]; then
>&2 echo "###"
>&2 echo "### $PROGNAME $*"
>&2 echo "###"
fi
}
while getopts :n:s:m:qd opt; do
case $opt in
d)
DRYRUN=true
;;
q)
QUIET=true
;;
m)
MAX_PODS=$OPTARG
;;
n)
NAMESPACE="-n $OPTARG"
;;
s)
SERVICE=$OPTARG
;;
\?)
usage
exit 0
;;
esac
done
if [ -z $SERVICE ]; then
usage
exit 1
fi
shift $(expr $OPTIND - 1)
while test "$#" -gt 0; do
if [ "$REST" == "" ]; then
REST="$1"
else
REST="$REST $1"
fi
shift
done
if [ "$REST" == "" ]; then
usage
exit 1
fi
PODS=()
for pod in $(kubectl $NAMESPACE get pods --output=jsonpath={.items..metadata.name}); do
echo $pod | grep -qe "^$SERVICE" >/dev/null 2>&1
if [ $? -eq 0 ]; then
PODS+=($pod)
fi
done
if [ ${#PODS[#]} -eq 0 ]; then
echo "service not found in ${NAMESPACE:-default}: $SERVICE"
exit 1
fi
if [ ! -z $MAX_PODS ]; then
PODS=("${PODS[#]:0:$MAX_PODS}")
fi
header "{pods: ${#PODS[#]}, command: \"$REST\"}"
for i in "${!PODS[#]}"; do
pod=${PODS[$i]}
header "{pod: \"$(($i + 1))/${#PODS[#]}\", name: \"$pod\"}"
if [ "$DRYRUN" != "true" ]; then
kubectl $NAMESPACE exec $pod -- $REST
fi
done

Answer 3

Here:
kubectl -n alex get pods -l app=alex-admin-api -o name | xargs -I{} kubectl -n alex exec {} -- cat alexAdminApi.log >> alex-admin-api_pods.logs

Answer 4

I have written a simple kubectl plugin that "boardcast"s commands to all pods, using Tmux. Assuming that all your pods in the service should share the same labels in their spec, app=foobar for instance, you can use the command below,
kubectl tmux-exec -l app=foobar bash
The plugin is available on Github: predatorray/kubectl-tmux-exec. Hope it will help you!

Answer 5

there is also a kubectl plugin called kubectl-exec-all https://github.com/jpdasma/kubectl-exec-all that is doing a good job.
Can't work with krew index but you can save the content of https://raw.githubusercontent.com/jpdasma/kubectl-exec-all/master/unix/exec-all.sh to /usr/local/bin/kubectl-exec_all and don't forget to make it executable by running
chmod +x /usr/local/bin/kubectl-exec_all
then it work like this:
kubectl plugin exec-all daemonset docker-daemon -- docker system prune -a -f