kail: kubernetes tail

Kubernetes tail. Streams logs from all containers of all matched pods. Match pods by service, replicaset, deployment, and others. Adjusts to a changing cluster - pods are added and removed from logging as they fall in or out of the selection.

Usage

With no arguments, kail matches all pods in the cluster. You can control the matching pods with arguments which select pods based on various criteria.

All flags can be set by an environment variable - KAIL_POD=foo kail is the same as kail --pod foo.

Selectors

Flag	Selection
-l, --label LABEL-SELECTOR	match pods based on a standard label selector
-p, --pod NAME	match pods by name
-n, --ns NAMESPACE-NAME	match pods in the given namespace
--svc NAME	match pods belonging to the given service
--rc NAME	match pods belonging to the given replication controller
--rs NAME	match pods belonging to the given replica set
-d, --deploy NAME	match pods belonging to the given deployment
--sts NAME	match pods belonging to the given statefulset
-j, --job NAME	match pods belonging to the given job
--node NODE-NAME	match pods running on the given node
--ing NAME	match pods belonging to services targeted by the given ingress
-c, --containers CONTAINER-NAME	restrict which containers logs are shown for
--ignore LABEL-SELECTOR	Ignore pods that the selector matches. (default: kail.ignore=true)
--current-ns	Match pods in the namespace specified in Kubernetes' "current context"
--ignore-ns NAME	Ignore pods in the given namespaces. Overridden by --ns, --current-ns. (default: kube-system)

Name Selection

When selecting objects by NAME (--svc, --pod, etc...), you can either qualify it with a namespace to restrict the selection to the given namespace, or select across all namespaces by giving just the object name.

Example:

# match pods belonging to a replicaset named 'workers' in any namespace.
$ kail --rs workers

# match pods belonging to the replicaset named 'workers' only in the 'staging' namespace
$ kail --rs staging/workers

Combining Selectors

If the same flag is used more than once, the selectors for that flag are "OR"ed together.

# match pods belonging to a replicaset named "workers" or "db"
$ kail --rs workers --rs db

Different flags are "AND"ed together:

# match pods belonging to both the service "frontend" and the deployment "webapp"
$ kail --svc frontend --deploy webapp

Other Flags

Flag	Description
-h, --help	Display help and usage
--context CONTEXT-NAME	Use the given Kubernetes context
--dry-run	Print initial matched pods and exit
--log-level LEVEL	Set the logging level (default: error)
--log-file PATH	Write output to PATH (default: /dev/stderr)
--since DURATION	Display logs as old as given duration. Ex: 5s, 2m, 1.5h or 2h45m (defaults: 1s). See here for more information on the duration format.
-o, --output	You can choose to display logs in default, raw (without prefix), json, pretty json and zerolog formats.

Installing

Homebrew

$ brew tap boz/repo
$ brew install boz/repo/kail

Krew

$ kubectl krew install tail
$ kubectl tail -h

Downloading

Kail binaries for Linux and OSX can be found on the latest release page. Download and install into your $GOPATH/bin.

Running in a cluster with kubectl

The docker image abozanich/kail is available for running kail from within a kubernetes pod via kubectl.

Note: be sure to include the kail.ignore=true label, otherwise... it's logging all the way down.

Example:

# match all pods - synonymous with 'kail' from the command line
$ kubectl run -it --rm -l kail.ignore=true --restart=Never --image=abozanich/kail kail

# match pods belonging to service 'api' in any namespace - synonymous with 'kail --svc api'
$ kubectl run -it --rm -l kail.ignore=true --restart=Never --image=abozanich/kail kail -- --svc api

Building

Install build and dev dependencies

• govendor
• minikube
• linux only: musl-gcc for building docker images.

Install source code and golang dependencies

$ go get -d github.com/boz/kail
$ cd $GOPATH/src/github.com/boz/kail
$ make install-deps

Build binary

$ make

Install run against a demo cluster

$ minikube start
$ ./_example/demo.sh start
$ ./kail

# install image into minikube and run via kubectl
$ make image-minikube
$ kubectl run -it --rm -l kail.ignore=true --restart=Never --image=kail kail

Stress testing

Start minikube with a fair amount of CPU and memory.

$ minikube start --cpus 4 --memory 8192

Start stress.yml resources.

$ kubectl create -f _example/stress.yml

Wait a while for the pods to run

$ kubectl get pods --namespace stress | grep Running | wc -l
100

Run kail

./kail --ns stress