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 created by a certain replication controller

User · Answer

In this example  you can replace the  lt namespace gt  and  lt app-name gt  to get the logs when there are multiple Containers defined in a Pod  kubectl -n  lt namespace gt  logs -f deployment  lt app-name gt        --all-containers true --since 10m

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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

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Worked for me   kubectl logs -n namespace -l app label -c container

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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

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To build on the previous answer if you add -f you can tail the logs   kubectl logs -f deployment app

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Not sure if this is a new thing  but with deployments it is possible to do it like this   kubectl logs deployment app1

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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  lt one of your pods gt  -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

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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

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Another solution that I would consider is using K9S which is a great kube administration tool  After installation  the usage is very straightforward   k9s -n my-namespace --context the context name in kubeconfig   If kubeconfig is not in the default location add KUBECONFIG path to kubeconfig prefix   The default view will list all pods as a list   We can change the view to other Kube controllers like replica set  question asked for replication controllers so notice they are deprecated   deployments  cron jobs  etc  by entering a colon   and start typing the desired controller - as we can see K9S provides autocompletion for us   And we can see all replica sets in the current namespace   We can just choose the desired replica set by clicking enter and then we ll see the list of all pods which are related to this replica set - we can then press on  l  to view logs of each pod  So  unlike in the case of stern  we still need to go on each pod and view its logs but I think it is very convenient with K9S - we first view all pods of a related controller and then investigate logs of each pod by simply navigating with enter  l and escape

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I use this command   kubectl -n  lt namespace gt  logs -f deployment  lt app-name gt  --all-containers true --since 10m

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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

User · Answer

You can also do this by service name   First  try to find the service name of the respective pod which corresponds to multiple pods of the same service  kubectl get svc   Next  run the following command to display logs from each container   kubectl logs -f service  lt service-name gt

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If the pods are named meaningfully one could use simple Plain Old Bash   keyword nodejs command  cat  lt    for line in   kubectl get pods       grep  keyword   grep Running   awk   print  1     do      command   command  kubectl logs --tail 2 -f  line  amp    amp  amp      done command   command echo   eval  command   Explanation  Loop through running pods with name containing  nodejs   Tail the log for each of them in parallel  single ampersand runs in background  ensuring that if any of the pods fail the whole command exits  double ampersand   Cat the streams from each of the tail commands into a unique stream  Eval is needed to run this dynamically built command

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Previously provided solutions are not that optimal  The kubernetes team itself has provided a solution a while ago  called stern   stern app1   It is also matching regular expressions and does tail and -f  follow  by default  A nice benefit is  that it shows you the pod which generated the log as well   app1-12381266dad-3233c foobar log app1-99348234asd-959cc foobar log2   Grab the go-binary for linux or install via brew for OSX    https   kubernetes io blog 2016 10 tail-kubernetes-with-stern   https   github com wercker stern

User · Answer

You can use labels  kubectl logs -l app elasticsearch

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

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