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
/ 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

WinGet (Windows)

If you're running on Windows, usually the actual best way is to use WinGet to install which is Windows' built-in package manager, you can install like this:

winget install stern.stern

Usage

stern pod-query [flags]

The pod-query is a regular expression or a Kubernetes resource in the form /.

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 / (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.
--burst | 0 | Maximum burst for throttle to the Kubernetes API server. Defaults to 0 (use client-go default). Ignored when --qps=-1.
--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'.
--condition | | The condition to filter on: [condition-name[=condition-value]. The default condition-value is true. Match is case-insensitive. Currently only supported with --tail=0 or --no-follow.
--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.
--qps | 0 | Maximum QPS to the Kubernetes API server. Defaults to 0 (use client-go default). Use -1 to disable client-side throttling.
--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.
<!-- auto generated cli flags end --->

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.

yaml
# : 
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 |
| Timestamp | string | The log timestamp formatted per --timestamps/--timezone, empty unless --timestamps is set |
| 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 |
| Labels | map[string]string | The labels of the pod |
| Annotations | map[string]string | The annotations of the pod |

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 |
| colorCustom | string, int [, int] | Print text using custom color, i.e. {{color "Hi" 3 96}} will print "Hi" as italic with cyan 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

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