How do I get logs from all pods of a Kubernetes replication controller?

Question

Running kubectl logs shows me the stderr/stdout of one Kubernetes container.

How can I get the aggregated stderr/stdout of a set of pods, preferably those

Answer 1

Not sure if this is a new thing, but with deployments it is possible to do it like this:

kubectl logs deployment/app1

Answer 2

I've created a small bash script called kubetail that makes this possible. For example to tail all logs for pods named "app1" you can do:

kubetail app1

You can find the script here.

Answer 3

One option is to set up cluster logging via Fluentd/ElasticSearch as described at https://kubernetes.io/docs/user-guide/logging/elasticsearch/. Once logs are in ES, it's easy to apply filters in Kibana to view logs from certain containers.

Answer 4

I use this simple script to get a log from the pods of a deployment:

#!/usr/bin/env bash

DEPLOYMENT=$1

for p in $(kubectl get pods | grep ^${DEPLOYMENT}- | cut -f 1 -d ' '); do 
    echo --------------------------- 
    echo $p 
    echo --------------------------- 
    kubectl logs $p
done

Gist of the script

Usage: log_deployment.sh "deployment-name".

Script will then show log of all pods that start with that "deployment-name".

Answer 5

You can get the logs from multiple containers using labels as Adrian Ng suggested:

kubectl logs --selector app=yourappname

In case you have a pod with multiple containers, the above command is going to fail and you'll need to specify the container name:

kubectl logs --selector app=yourappname --container yourcontainername

Note: If you want to see which labels are available to you, the following command will list them all:

kubectl get pod <one of your pods> -o template --template='{{.metadata.labels}}'

...where the output will look something like

map[app:yourappname controller-revision-hash:598302898 pod-template-generation:1]

Note that some of the labels may not be shared by other pods - picking "app" seems like the easiest one

Answer 6

You can get help from kubectl logs -h and according the info,

kubectl logs -f deployment/myapp -c myapp --tail 100

-c is the container name and --tail will show the latest num lines，but this will choose one pod of the deployment, not all pods. This is something you have to bear in mind.

kubectl logs -l app=myapp -c myapp --tail 100

If you want to show logs of all pods, you can use -l and specify a lable, but at the same time -f won't be used.