Convenience script to intelligently connect to a kubernetes pod/node given the API name

ssh_to.sh

#!/usr/bin/env bash

set -eu

readonly mode="${1:-}"
readonly target="${2:-}"

readonly ssh_key_path="path_to_kops_ssh_key"

die() {
  local -r msg="${1:-}"

  echo "${msg}"
  exit 1
}

if [ "pod" != "${mode}" ] && [ "node" != "${mode}" ]; then
  die "ERROR: unknown mode [${mode}] must be one of [pod, node]"
fi

if [ -z "${target}" ]; then
  die 'ERROR: must provide a target'
fi

target_looks_like_a_node() {
  echo "${target}" | grep -Eq "\.ec2\.internal"
}

get_node_from_pod() {
  local -r pod="${1}"

  kubectl get pod/"${pod}" -o go-template="{{.spec.nodeName}}" 2>/dev/null || echo ''
}

get_external_ip_from_node() {
  local -r node="${1}"

  kubectl get node/"${node}" -o go-template='{{range .status.addresses}}{{if eq .type "ExternalIP"}}{{.address}}{{end}}{{end}}' 2>/dev/null || echo ''
}

verify_is_node() {
  local -r node="${1}"

  (kubectl get nodes -o custom-columns=NAME:.metadata.name |  grep -q "${node}") || die "ERROR: not a valid node [${node}]"
}

verify_is_pod() {
  local -r pod="${1}"

  (kubectl get pods -o custom-columns=NAME:.metadata.name |  grep -q "${pod}") || die "ERROR: not a valid pod [${pod}]"
}

connect_to_node() {
  local -r target_node="${1}"

  verify_is_node "${target_node}"

  local -r node_ip="$( get_external_ip_from_node "${target_node}" )"

  echo "> ssh'ing to node [${node_ip}]"
  ssh -i "${ssh_key_path}" admin@"${node_ip}"
}

connect_to_pod() {
  local -r target_pod="${1}"

  verify_is_pod "${target_pod}"

  echo "> connecting to pod [${target_pod}]"
  kubectl exec -it "${target_pod}" --container server -- /bin/sh
}

main() {
  if [ "pod" == "${mode}" ]; then
    target_looks_like_a_node && die "It appears you provided a node [${target}]"

    connect_to_pod "${target}"
  elif [ "node" == "${mode}" ]; then
    local node="${target}"
    if ! target_looks_like_a_node; then
      node="$( get_node_from_pod "${target}" )"
      if [ -z "${node}" ]; then
        die "ERROR: unable to resolve node for target [${target}]"
      fi
    fi

    connect_to_node "${node}"
  fi
}

main