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Kubectl logging

Kubectl logging#

This page describes how to look at various logs by using some deployer commands that wrap the most common kubectl commands or by using kubectl directly.

Look at logs via deployer sub-commands#

There are some deployer debug sub-commands that wrap up the most relevant kubectl logs arguments that allow conveniently checking logs with only one command.

Tip

You can export the cluster’s and hub’s names as environmental variables to directly use the copy-pasted commands in the sections below.

export CLUSTER_NAME=2i2c; export HUB_NAME=staging

Look at hub component logs#

The JupyterHub component’s logs can be fetched with the deployer debug component-logs command, ran for each hub component.

These commands are standalone and don’t require running deployer use-cluster-credentials before.

Tip

  1. The --no-follow flag

    You can pass --no-follow to each of the deployer commands below to provide just logs up to the current point in time and then stop.

  2. The --previous flag

    If the pod has restarted due to an error, you can pass --previous to look at the logs of the pod prior to the last restart.

Hub pod logs#

deployer debug component-logs $CLUSTER_NAME $HUB_NAME hub

Proxy pod logs#

deployer debug component-logs $CLUSTER_NAME $HUB_NAME proxy

Traefik pod logs#

deployer debug component-logs $CLUSTER_NAME $HUB_NAME traefik

Look at dask-gateway logs#

Display the logs from the dask-gateway’s most important component pods.

Dask-gateway-api pod logs#

deployer debug component-logs $CLUSTER_NAME $HUB_NAME dask-gateway-api

Dask-gateway-controller pod logs#

deployer debug component-logs $CLUSTER_NAME $HUB_NAME dask-gateway-controller

Look at a specific user’s logs#

Display logs from the notebook pod of a given user with the following command:

deployer debug user-logs  $CLUSTER_NAME $HUB_NAME <username>

Note that you don’t need the escaped username, with this command.

Look at logs via kubectl#

Pre-requisites#

Get the name of the cluster you want to debug and export its name as env vars. Then use the deployer to gain kubectl access into this specific cluster.

Example:

export CLUSTER_NAME=2i2c;
deployer use-cluster-credentials $CLUSTER_NAME

Kubernetes autoscaler logs#

You can find scale up or scale down events by looking for decision events

kubectl describe -n kube-system configmap cluster-autoscaler-status

Kubernetes node events and status#

  1. Running nodes and their status

    kubectl get nodes

  2. Get a node’s events from the past 1h

    kubectl get events --field-selector involvedObject.kind=Node --field-selector involvedObject.name=<some-node-name>

  3. Describe a node and any related events

    kubectl describe node <some-node-name> --show-events=true

Kubernetes pod events and status#

Tip

The following commands require passing the namespace where a specific pod is running. Usually this namespace is the same with the hub name.

  1. Running pods in a namespace and their status

    kubectl get pods -n <namespace>

  2. Running pods in all namespaces of the cluster and their status

    kubectl get pods --all-namespaces

  3. Get a pod’s events from the past 1h

    kubectl get events --field-selector involvedObject.kind=Pod --field-selector involvedObject.name=<some-pod-name>

  4. Describe a pod and any related events

    kubectl describe pod <some-pod-name> --show-events=true

Kubernetes pod logs#

You can access any pod’s logs by using the kubectl logs commands. Below are some of the most common debugging commands.

Tip

  1. The --follow flag

    You can pass the --follow flag to each of the kubectl logs command below to stream the logs as they are happening, otherwise, they will just be presented up to the current point in time and then stop.

  2. The --previous flag

    If the pod has restarted due to an error, you can pass --previous to look at the logs of the pod prior to the last restart.

  3. The --tail flag

    With --tail=<number> flag you can pass the number of lines of recent log file to display, otherwise, it will show all log lines.

  4. The --since flag

    This flag can be used like --since=1h to only return logs newer than 1h in this case, or any other relative duration like 5s, 2m, or 3h.

  1. Print the logs of a pod

    kubectl logs <pod_name> --namespace <pod_namespace>

  2. Print the logs for a container in a pod

    kubectl logs -c <container_name> <pod_name> --namespace <pod_namespace>

  3. View the logs for a previously failed pod

    kubectl logs --previous <pod_name> --namespace <pod_namespace>

  4. View the logs for all containers in a pod

    kubectl logs <pod_name> --all-containers --namespace <pod_namespace>
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