Tail kubectl logs from multiple selected pods with colorized output.

pod-logs.bash

#!/bin/bash
set -euo pipefail

# Tail kubectl logs from multiple selected pods with colorized output.

function usage() {
    local name="$(basename "${BASH_SOURCE[0]}")"

    echo "Synopsis:"
    echo -e "\t$name -n NAMESPACE -l SELECTOR [ -- KUBECTL_LOGS_ARGS ]\n"
    echo "Options:"
    echo -e "\t-n NAMESPACE\tThe Kubernetes namespace used."
    echo -e "\t-l SELECTOR\tKubernetes selector expression used to find pods."
    echo "Usage:"
    echo -e "\t$name -n production -l name=foo -- --timestamps --tail=10\n"

    exit 1
}

NAMESPACE=
SELECTOR=

# Ensure OPTIND is properly initialized.
OPTIND=1

# Parse program arguments.
while getopts ":h?n:l:" opt; do
    case "$opt" in
    h|\?)
        usage
        ;;
    n)
        NAMESPACE="$OPTARG"
        ;;
    l)
        SELECTOR="$OPTARG"
        ;;
    esac
done

shift $(( OPTIND - 1 ))

if [ "${1:-}" = "--" ]; then
    shift
fi

# Validate program arguments.
if [ -z "$NAMESPACE" ] || [ -z "$SELECTOR" ]; then
    usage
fi


# Array of process ids of background jobs created by this process.
declare -a PIDS

# Kill child processes when interrupted.
trap 'exit' INT TERM ERR
trap 'kill 0' EXIT


# Array of ANSI escape codes for colors.
declare -a COLORS
for color in {31..37}; do
    COLORS+=("\033[0;${color}m")
done
for color in {91..96}; do
    COLORS+=("\033[0;${color}m")
done

# Number of colors.
NCOLORS="${#COLORS[@]}"


# Names of pods whose logs we want to follow.
PODS=( \
    $(kubectl get pod -ojsonpath='{range .items[*]}{.metadata.name}{"\n"}{end}' -n "$NAMESPACE" -l "$SELECTOR") \
)

# Start tailing each pod in the background with colorized output.
for i in ${!PODS[@]}; do
    if [ $i -ge $NCOLORS ]; then
        i=$(( $i % $NCOLORS ))
    fi

    ( kubectl logs "pod/${PODS[i]}" -n "$NAMESPACE" -f $@ \
        | awk -v color="${COLORS[i]}" -v pod="${PODS[i]}" '{ printf "%s%s ", color, pod; print }' ) &

    PIDS+=( $! )
done


# Wait for background jobs.
wait ${PIDS[@]}