Collect multiple K8S resources into YAML files based on a grep expression

collect_k8s_resources_by_expression.sh

#!/bin/bash

set -e
set -u
set -o pipefail

######################################## DESCRIPTION #############################################################
## Use this script to collect multiple resources into YAML files.                                               ##
##                                                                                                              ##
## The mandatory '--exp' option takes a grep expression to match against all 'kind.group'.                      ##
##                                                                                                              ##
## i.e. 'collect_k8s_resources_by_expression.sh --exp monitoring.coreos.com'                                    ##
## will result in a 'collected' directory with a bunch of YAML files for every CR in monitoring.coreos.com.     ##
## doing '--exp coreos.com' might include a broader wide of YAML files as we grep over `kubectl api-resources`. ##
## the more specific the expression, the last YAML files we'll get, and the less time this script takes to run. ##
##                                                                                                              ##
## OVERUSAGE WARNING: will result in a lot of API requests and a lengthy runtime,                               ##
## think about your expression b4 running it!                                                                   ##
##################################################################################################################

####################################### USAGE EXAMPLES ############################################
## bash ./collect_k8s_resources_by_expression.sh --exp coreos.com                                ##
## bash ./collect_k8s_resources_by_expression.sh --exp coreos.com --dir collected                ##
## bash ./collect_k8s_resources_by_expression.sh --exp coreos.com --dir collected --nonamespaced ##
## bash ./collect_k8s_resources_by_expression.sh --exp coreos.com --dir collected --noclustered  ##
## bash ./collect_k8s_resources_by_expression.sh --exp coreos.com --clean                        ##
###################################################################################################

# iterate over arguments and create named parameters
while [ $# -gt 0 ]; do
  if [[ $1 == *"--"* ]]; then
    param="${1/--/}"
    if [ -z ${2+x} ] || [[ $2 = --* ]]; then
      declare $param="true"
    else
      declare $param="$2"
    fi
  fi
  shift
done

# set non-required parameters defaults
dir=${dir:-collected}
nonamespaced=${nonamespaced:-false}
noclustered=${noclustered:-false}
clean=${clean:-false}

# verify required parameters
if [ -z ${exp+x} ]; then
  echo "ERROR: You must specify a grep expression using the '--exp' option. i.e. a partial resource group."
  exit 1
fi
if [ $nonamespaced = "true" ] && [ $noclustered = "true" ] ; then
  echo "ERROR: The '--nonamespaced' skips namespace resources, the '--noclustered' skips cluster ones, these cannot be combined."
  exit 1
fi

# get kind from 'kind.group'
get_kind() {
  IFS='.' kgsplit=($1)
  echo ${kgsplit[0]}
}

# get name from kind.group/name
get_name_cluster() {
  IFS='/' kgsplit=($1)
  echo ${kgsplit[1]}
}

# gather 'kubectl get' commands
commands=()

# use the --nonamespaced option to disable namespace resources fetch
if [ $nonamespaced != "true" ]; then
  # grab namespaced api resources
  namepsaced=`kubectl api-resources --no-headers --namespaced=true -o name | grep $exp`

  if [ -z "$namepsaced" ]; then
    echo "WARN: no namespaced resources matching regex expression '$exp' found"
  else
    records=($namepsaced)
    for rec in "${records[@]}"; do
      crs=`kubectl get $rec -A -o 'custom-columns=ns:.metadata.namespace,n:.metadata.name' --no-headers`
      if [ ! -z "$crs" ]; then
        kind=$(get_kind $rec)
        IFS=$'\n' resources=($crs)
        for res in "${resources[@]}"; do
          sanitized=`echo $res | xargs`
          target="$dir"/"$kind"_"${sanitized// /_}.yaml"
          commands+=("kubectl get $rec -n $sanitized -o yaml > $target")
        done
      fi
    done
  fi
fi

# use the --noclustered option to disable cluster resources fetch
if [ $noclustered != "true" ]; then
  # grab clustrer api resources
  clustered=`kubectl api-resources --namespaced=false -o name | grep $exp`

  if [ -z "$clustered" ]; then
    echo "WARN: no clustered resources matching regex expression '$exp' found"
  else
    records=($clustered)
    for rec in "${records[@]}"; do
      crs=`kubectl get $rec -o name --no-headers`
      if [ ! -z "$crs" ]; then
        kind=$(get_kind $rec)
        IFS=$'\n' resources=($crs)
        for res in "${resources[@]}"; do
          name=$(get_name_cluster $res)
          target="$dir"/"$kind"_"cluster_$name.yaml"
          commands+=("kubectl get $rec $name -o yaml > $target")
        done
      fi
    done
  fi
fi


# clean target directory
if [ $clean = "true" ]; then
  rm -rf $dir
fi

# create target directory if doesn't exists
if [ ! -d "$dir" ]; then
  mkdir -p $dir
fi

# remove (if) existing commands file
rm -f $dir/commands

# list and evaluate all commands - will result in a list-file and 0-to-many CR yaml files
for cmd in "${commands[@]}"; do
  echo $cmd >> $dir/commands
  eval $cmd
done