I have developed a web microservice in Golang. I have used zap logger to log the application log in a file at location /var/log/myapp/myapp.log.
I want to see log information in file myapp.log through below command:
#kubectl logs mayappPod
But it is not working as by default STDOUT and STDERR output is redirected to kubectl logs command.
So my question is what exactly I am supposed to do to see the /var/log/myapp/myapp.log log through kubectl logs command.
Thanks,
Rohit
kubectl logs command just show you logs from container(s) you specified. And container got logs from STDOUT and STDERR.
The recommended way is to setup your logging library to write logs to STDOUT. But as a workaround you can create symlink from /var/log/myapp/myapp.log to /dev/stdout in your docker container.
Another option is not use kubectl logs at all. You could copy this log file from your pod using kubectl cp <some-namespace>/<some-pod>:/tmp/foo /tmp/bar see
Related
I use k9s to access the bash from the pod where I keep the logs of my project.
Reading the logs with a cat is annoying, so I want to send them to my pc.
How can I do this?
You can use kubectl cp command.
kubectl cp default/<some-pod>:/logs/app.log app.log
Is it possible to run a linux command against a process which is running inside a kubernetes pod. Example: I want to grab heapdumps on a java process running inside a k8 pod. The pod comes with minimal installation and does not have that much disk space either, so I want to run jmap command from local machine (pointing to k8 cluster). Thanks.
As I have already mentioned in the comments, what you can use is the kubectl exec command:
Execute a command in a container.
Usage:
$ kubectl exec (POD | TYPE/NAME) [-c CONTAINER] [flags] -- COMMAND [args...]
The kubectl exec command is a tool that allows you to inspect and debug your applications, by executing commands inside your containers.
If you need more details and examples regarding how to use it, I recommend these two guides:
Get a Shell to a Running Container: This page shows how to use kubectl exec to get a shell to a running container.
How does kubectl exec work?
kubectl exec did it. It allows to run any command inside the container. For example:
kc exec <POD_NAME> -- jmap -dump:live,format=b,file=heapdump.bin <pid>
When i issue
kubectl logs MY_POD_NAME --limit-bytes=1
command, the --limit-bytes option is ignored and i get all the pod's logs.
My kubernetes version is 1.15.3
Trying to understand why that would be. When i issue the same command in GKE setup, the --limit-bytes option works as expected. I wonder what might be different in my setup to prevent this option from working correctly. (This is on CentOS).
Update: i tracked down the issue to Docker's --log-driver option.
If the Docker --log-driver is set to 'json-file', then kubectl logs command works fine with --limit-bytes option. However, if the Docker -log-driver is set to 'journald', then kubectl logs command ignores the --limit-bytes option. Seems like a kubectl bug to me.
After executing this command you shoud have seen following error:
error: expected 'logs [-f] [-p] (POD | TYPE/NAME) [-c CONTAINER]'.
POD or TYPE/NAME is a required argument for the logs command
See 'kubectl logs -h' for help and examples.
Execute:
$ kubectl logs your_pod_name -c container_name --limit-bytes=1 -n namespace_name
If you set --limit-bytes flag you must know that
--limit-bytes=0: Maximum bytes of logs to return.
Defaults to no limit.=0: Maximum bytes of logs to return. Defaults to no limit.
Documentation of kubectl-logs.
Please let me know if it helps.
Yeah, it should work fine -
Please try this, if you have one container in application -
kubectl -n namespace logs pod_name --limit-bytes=1
If you have multiple containers then please mention like -
kubectl -n namespace logs pod_name -c container_name --limit-bytes=1
How do I run docker-compose logs but using a separate yaml config?
For example, if I want to run docker-compose up with a separate file, I can do:
docker-compose -f other-config.yml up
But -f in docker-compose logs points to a service, rather than a file.
For docker-compose, the -f options means to load a different configurations file. for docker-compose logs, the -f option means to follow the logs.
For your situation you need to pass the -f option twice:
docker-compose -f other-config.yml logs -f
You can optionally specify a service name as well at the end.
Please before you comment or answer, this question is about a CLI program, not a service. Apparently 90% of Kubernetes has to do with running services, so there is sparse documentation for CLI programs meant to be part of a pipeline workflow.
I have a command line program that uses stdout for JSON results.
I have a docker image for the command line program.
If I create the container as a Kubernetes Job, than stdout and stderr are mixed and require heuristic scrubbing to get pure JSON out.
The stderr messages are from native libraries outside of my direct control.
Supposedly, if I run kubectl exec against a running pod, I will get the normal stdout/stderr pipes.
Is there a way to just have the pod running without an entrypoint (or some dummy service entrypoint) with the sole purpose of running kubectl exec against it?
Is there a way to just have the pod running without an entrypoint [...]?
A pod consists of one or more containers, each of which has an individual entrypoint. It is certainly possible to run a container with a dummy command, for example, you can build an image with:
CMD sleep inf
This will run a container that will persist until you kill it, and you could happily docker exec into it.
You can apply the same solution to k8s. You could build an image as described above and deploy that in a pod, or you could use an existing image and simply set the command, as in:
spec:
containers:
- name: mycontainer
image: myexistingimage
command: ["sleep", "inf"]
You can use kubectl as docker cli https://kubernetes.io/docs/reference/kubectl/docker-cli-to-kubectl/
kubectl run just do the job. There is no need for a workaround.
Aditionally, you can attach I/O and disable automatic restart:
kubectl run -i -t busybox --image=busybox --restart=Never