Awesome
stern
Fork of discontinued wercker/stern
Stern allows you to tail multiple pods on Kubernetes and multiple containers
within the pod. Each result is color coded for quicker debugging.
The query is a regular expression or a Kubernetes resource in the form
<resource>/<name> so the pod name can easily be filtered and
you don't need to specify the exact id (for instance omitting the deployment
id). If a pod is deleted it gets removed from tail and if a new pod is added it
automatically gets tailed.
When a pod contains multiple containers Stern can tail all of them too without
having to do this manually for each one. Simply specify the container flag to
limit what containers to show. By default all containers are listened to.
Installation
Download binary
Download a binary release
Build from source
go install github.com/stern/stern@latest
asdf (Linux/macOS)
If you use asdf, you can install like this:
asdf plugin-add stern
asdf install stern latest
Homebrew (Linux/macOS)
If you use Homebrew, you can install like this:
brew install stern
Krew (Linux/macOS/Windows)
If you use Krew which is the package manager for kubectl plugins, you can install like this:
kubectl krew install stern
Usage
stern pod-query [flags]
The pod-query is a regular expression or a Kubernetes resource in the form <resource>/<name>.
The query is a regular expression when it is not a Kubernetes resource,
so you could provide "web-\w" to tail web-backend and web-frontend pods but not web-123.
When the query is in the form <resource>/<name> (exact match), you can select all pods belonging
to the specified Kubernetes resource, such as deployment/nginx.
Supported Kubernetes resources are pod, replicationcontroller, service, daemonset, deployment,
replicaset, statefulset and job.
cli flags
<!-- auto generated cli flags begin --->| flag | default | purpose |
|---|---|---|
--all-namespaces, -A | false | If present, tail across all namespaces. A specific namespace is ignored even if specified with --namespace. |
--color | auto | Force set color output. 'auto': colorize if tty attached, 'always': always colorize, 'never': never colorize. |
--completion | Output stern command-line completion code for the specified shell. Can be 'bash', 'zsh' or 'fish'. | |
--config | ~/.config/stern/config.yaml | Path to the stern config file |
--container, -c | .* | Container name when multiple containers in pod. (regular expression) |
--container-colors | Specifies the colors used to highlight container names. Use the same format as --pod-colors. Defaults to the values of --pod-colors if omitted, and must match its length. | |
--container-state | all | Tail containers with state in running, waiting, terminated, or all. 'all' matches all container states. To specify multiple states, repeat this or set comma-separated value. |
--context | The name of the kubeconfig context to use | |
--diff-container, -d | false | Display different colors for different containers. |
--ephemeral-containers | true | Include or exclude ephemeral containers. |
--exclude, -e | [] | Log lines to exclude. (regular expression) |
--exclude-container, -E | [] | Container name to exclude when multiple containers in pod. (regular expression) |
--exclude-pod | [] | Pod name to exclude. (regular expression) |
--field-selector | Selector (field query) to filter on. If present, default to ".*" for the pod-query. | |
--highlight, -H | [] | Log lines to highlight. (regular expression) |
--include, -i | [] | Log lines to include. (regular expression) |
--init-containers | true | Include or exclude init containers. |
--kubeconfig | Path to the kubeconfig file to use for CLI requests. | |
--max-log-requests | -1 | Maximum number of concurrent logs to request. Defaults to 50, but 5 when specifying --no-follow |
--namespace, -n | Kubernetes namespace to use. Default to namespace configured in kubernetes context. To specify multiple namespaces, repeat this or set comma-separated value. | |
--no-follow | false | Exit when all logs have been shown. |
--node | Node name to filter on. | |
--only-log-lines | false | Print only log lines |
--output, -o | default | Specify predefined template. Currently support: [default, raw, json, extjson, ppextjson] |
--pod-colors | Specifies the colors used to highlight pod names. Provide colors as a comma-separated list using SGR (Select Graphic Rendition) sequences, e.g., "91,92,93,94,95,96". | |
--prompt, -p | false | Toggle interactive prompt for selecting 'app.kubernetes.io/instance' label values. |
--selector, -l | Selector (label query) to filter on. If present, default to ".*" for the pod-query. | |
--show-hidden-options | false | Print a list of hidden options. |
--since, -s | 48h0m0s | Return logs newer than a relative duration like 5s, 2m, or 3h. |
--stdin | false | Parse logs from stdin. All Kubernetes related flags are ignored when it is set. |
--tail | -1 | The number of lines from the end of the logs to show. Defaults to -1, showing all logs. |
--template | Template to use for log lines, leave empty to use --output flag. | |
--template-file, -T | Path to template to use for log lines, leave empty to use --output flag. It overrides --template option. | |
--timestamps, -t | Print timestamps with the specified format. One of 'default' or 'short' in the form '--timestamps=format' ('=' cannot be omitted). If specified but without value, 'default' is used. | |
--timezone | Local | Set timestamps to specific timezone. |
--verbosity | 0 | Number of the log level verbosity |
--version, -v | false | Print the version and exit. |
See stern --help for details
Stern will use the $KUBECONFIG environment variable if set. If both the
environment variable and --kubeconfig flag are passed the cli flag will be
used.
config file
You can use the config file to change the default values of stern options. The default config file path is ~/.config/stern/config.yaml.
# <flag name>: <value>
tail: 10
max-log-requests: 999
timestamps: short
You can change the config file path with --config flag or STERNCONFIG environment variable.
templates
stern supports outputting custom log messages. There are a few predefined
templates which you can use by specifying the --output flag:
| output | description |
|---|---|
default | Displays the namespace, pod and container, and decorates it with color depending on --color |
raw | Only outputs the log message itself, useful when your logs are json and you want to pipe them to jq |
json | Marshals the log struct to json. Useful for programmatic purposes |
extjson | Outputs extended JSON with colorized pod/container names |
ppextjson | Pretty-prints extended JSON with colorized pod/container names |
It accepts a custom template through the --template flag, which will be
compiled to a Go template and then used for every log message. This Go template
will receive the following struct:
| property | type | description |
|---|---|---|
Message | string | The log message itself |
NodeName | string | The node name where the pod is scheduled on |
Namespace | string | The namespace of the pod |
PodName | string | The name of the pod |
ContainerName | string | The name of the container |
The following functions are available within the template (besides the builtin functions):
| func | arguments | description |
|---|---|---|
json | object | Marshal the object and output it as a json text |
color | color.Color, string | Wrap the text in color (.ContainerColor and .PodColor provided) |
parseJSON | string | Parse string as JSON |
tryParseJSON | string | Attempt to parse string as JSON, return nil on failure |
extractJSONParts | string, ...string | Parse string as JSON and concatenate the given keys. |
tryExtractJSONParts | string, ...string | Attempt to parse string as JSON and concatenate the given keys. , return text on failure |
prettyJSON | any | Parse input and emit it as pretty printed JSON, if parse fails output string as is. |
toRFC3339Nano | object | Parse timestamp (string, int, json.Number) and output it using RFC3339Nano format |
toTimestamp | object, string [, string] | Parse timestamp (string, int, json.Number) and output it using the given layout in the timezone that is optionally given (defaults to UTC). |
levelColor | string | Print log level using appropriate color |
bunyanLevelColor | string | Print bunyan numeric log level using appropriate color |
colorBlack | string | Print text using black color |
colorRed | string | Print text using red color |
colorGreen | string | Print text using green color |
colorYellow | string | Print text using yellow color |
colorBlue | string | Print text using blue color |
colorMagenta | string | Print text using magenta color |
colorCyan | string | Print text using cyan color |
colorWhite | string | Print text using white color |
Log level verbosity
You can configure the log level verbosity by the --verbosity flag.
It is useful when you want to know how stern interacts with a Kubernetes API server in troubleshooting.
Increasing the verbosity increases the number of logs. --verbosity 6 would be a good starting point.
Max log requests
Stern has the maximum number of concurrent logs to request to prevent unintentional load to a cluster.
The number can be configured by the --max-log-requests flag.
The behavior and the default are different depending on the presence of the --no-follow flag.
--no-follow | default | behavior |
|---|---|---|
| specified | 5 | limits the number of concurrent logs to request |
| not specified | 50 | exits with an error when if it reaches the concurrent limit |
The combination of --max-log-requests 1 and --no-follow will be helpful if you want to show logs in order.
Customize highlight colors
You can configure highlight colors for pods and containers in the config file using a comma-separated list of SGR (Select Graphic Rendition) sequences, as shown below. If you omit container-colors, the pod colors will be used as container colors as well.
# Green, Yellow, Blue, Magenta, Cyan, White
pod-colors: "32,33,34,35,36,37"
# Colors with underline (4)
# If empty, the pod colors will be used as container colors
container-colors: "32;4,33;4,34;4,35;4,36;4,37;4"
This format enables the use of various attributes, such as underline, background colors, 8-bit colors, and 24-bit colors, if your terminal supports them.
The equivalent flags --pod-colors and --container-colors are also available. The following command applies 24-bit colors using the --pod-colors flag.
# Monokai theme
podColors="38;2;255;97;136,38;2;169;220;118,38;2;255;216;102,38;2;120;220;232,38;2;171;157;242"
stern --pod-colors "$podColors" deploy/app
Examples:
Tail all logs from all namespaces
stern . --all-namespaces
Tail the kube-system namespace without printing any prior logs
stern . -n kube-system --tail 0
Tail the gateway container running inside of the envvars pod on staging
stern envvars --context staging --container gateway
Tail the staging namespace excluding logs from istio-proxy container
stern -n staging --exclude-container istio-proxy .
Tail the kube-system namespace excluding logs from kube-apiserver pod
stern -n kube-system --exclude-pod kube-apiserver .
Show auth activity from 15min ago with timestamps
stern auth -t --since 15m
Show all logs of the last 5min by time, sorted by time
stern --since=5m --no-follow --only-log-lines -A -t . | sort -k4
Show auth activity with timestamps in specific timezone (default is your local timezone)
stern auth -t --timezone Asia/Tokyo
Follow the development of some-new-feature in minikube
stern some-new-feature --context minikube
View pods from another namespace
stern kubernetes-dashboard --namespace kube-system
Tail the pods filtered by run=nginx label selector across all namespaces
stern --all-namespaces -l run=nginx
Follow the frontend pods in canary release
stern frontend --selector release=canary
Tail the pods on kind-control-plane node across all namespaces
stern --all-namespaces --field-selector spec.nodeName=kind-control-plane
Tail the pods created by deployment/nginx
stern deployment/nginx
Pipe the log message to jq:
stern backend -o json | jq .
Only output the log message itself:
stern backend -o raw
Output using a custom template:
stern --template '{{printf "%s (%s/%s/%s/%s)\n" .Message .NodeName .Namespace .PodName .ContainerName}}' backend
Output using a custom template with stern-provided colors:
stern --template '{{.Message}} ({{.Namespace}}/{{color .PodColor .PodName}}/{{color .ContainerColor .ContainerName}}){{"\n"}}' backend
Output using a custom template with parseJSON:
stern --template='{{.PodName}}/{{.ContainerName}} {{with $d := .Message | parseJSON}}[{{$d.level}}] {{$d.message}}{{end}}{{"\n"}}' backend
Output using a custom template that tries to parse JSON or fallbacks to raw format:
stern --template='{{.PodName}}/{{.ContainerName}} {{ with $msg := .Message | tryParseJSON }}[{{ colorGreen (toRFC3339Nano $msg.ts) }}] {{ levelColor $msg.level }} ({{ colorCyan $msg.caller }}) {{ $msg.msg }}{{ else }} {{ .Message }} {{ end }}{{"\n"}}' backend
Pretty print JSON (if it is JSON) and output it:
# Will try to parse .Message as JSON and pretty print it, if not json will output as is
stern --template='{{ .Message | prettyJSON }}{{"\n"}}' backend
# Or with parsed json, will drop non-json logs because of `with`
stern --template='{{ with $msg := .Message | tryParseJSON }}{{ prettyJSON $msg }}{{"\n"}}{{end}}' backend
Load custom template from file:
stern --template-file=~/.stern.tpl backend
Trigger the interactive prompt to select an 'app.kubernetes.io/instance' label value:
stern -p
Output log lines only:
stern . --only-log-lines
Read from stdin:
stern --stdin < service.log
Completion
Stern supports command-line auto completion for bash, zsh or fish. stern --completion=(bash|zsh|fish) outputs the shell completion code which work by being
evaluated in .bashrc, etc for the specified shell. In addition, Stern
supports dynamic completion for --namespace, --context, --node, a resource query
in the form <resource>/<name>, and flags with pre-defined choices.
If you use bash, stern bash completion code depends on the bash-completion. On the macOS, you can install it with homebrew as follows:
# If running Bash 3.2
brew install bash-completion
# or, if running Bash 4.1+
brew install bash-completion@2
Note that bash-completion must be sourced before sourcing the stern bash
completion code in .bashrc.
source "$(brew --prefix)/etc/profile.d/bash_completion.sh"
source <(stern --completion=bash)
If installed via Krew, use:
source <(kubectl stern --completion bash)
complete -o default -F __start_stern kubectl stern
If you use zsh, just source the stern zsh completion code in .zshrc.
source <(stern --completion=zsh)
if you use fish shell, just source the stern fish completion code.
stern --completion=fish | source
# To load completions for each session, execute once:
stern --completion=fish >~/.config/fish/completions/stern.fish
Running with container
You can also use stern using a container:
docker run ghcr.io/stern/stern --version
If you are using a minikube cluster, you need to run a container as follows:
docker run --rm -v "$HOME/.minikube:$HOME/.minikube" -v "$HOME/.kube:/$HOME/.kube" -e KUBECONFIG="$HOME/.kube/config" ghcr.io/stern/stern .
You can find image tags in https://github.com/orgs/stern/packages/container/package/stern.
Running in Kubernetes Pods
If you want to use stern in Kubernetes Pods, you need to create the following ClusterRole and bind it to ServiceAccount.
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
name: stern
rules:
- apiGroups: [""]
resources: ["pods", "pods/log"]
verbs: ["get", "watch", "list"]
Contributing to this repository
Please see CONTRIBUTING for details.