Deploying the latest build of a template (machine) image with #Xen #Orchestrator

In my current role we are using Packer to build images on a Xen Orchestrator environment, use a CI/CD system to install that image into both a Xen Template and an AWS AMI, and then we use Terraform to use that image across our estate. The images we build with Packer have this stanza in it:

locals {
  timestamp = regex_replace(timestamp(), "[- TZ:]", "")
}
variable "artifact_name" {
  default = "SomeLinux-version.iso"
}
source "xenserver-iso" "this" {
  vm_name = "${var.artifact_name}-${local.timestamp}"
  # more config below
}

As a result, the built images include a timestamp.

When we use the AMI in Terraform, we can locate it with this code:

variable "ami_name" {
  default = "SomeLinux-version.iso-"
}

data "aws_ami" "this" {
  most_recent = true

  filter {
    name   = "name"
    values = [var.ami_name]
  }

  filter {
    name   = "virtualization-type"
    values = ["hvm"]
  }

  owners = [var.owner]
}

But, because Xen doesn’t track when a template is created, instead I needed to do something different. Enter get_xoa_template.sh.

	#!/bin/bash
	trap cleanup SIGINT SIGTERM EXIT
	exit_message=""
	set_exit=0
	fail() {
	[ -n "$1" ] && echo "$1" >&2
	[ "$2" -gt 0 ] && exit $2
	}
	cleanup() {
	trap – SIGINT SIGTERM EXIT
	[ "$UNREGISTER" -eq 1 ] && [ "$STATE" == "signed_in" ] && xo-cli –unregister 2>&1
	[ -n "$exit_message" ] && fail "$exit_message" $set_exit
	}
	log_debug() {
	[ -n "$DEBUG" ] && echo "$1" >> "$DEBUG"
	}
	parse_params() {
	UNREGISTER=1
	DEBUG=""
	while :; do
	case "${1-}" in
	-h | –help)
	echo "usage: get_xoa_template.sh –template SomeTemplatePrefix" >&2
	echo "" >&2
	echo "Options:" >&2
	echo " -t | –template MyTemplatePrefix = The template to look for (required)" >&2
	echo " -s | –server ws://192.0.2.1 = Sign into Xen Orchestrator on 192.0.2.1" >&2
	echo " [Default to using XOA_URL environment variable]" >&2
	echo " -u | –user username@example.org = Sign into Xen Orchestrator using this username" >&2
	echo " [Default to using XOA_USER environment variable]" >&2
	echo " -p | –password hunter2 = Sign into Xen Orchestrator using this password" >&2
	echo " [Default to using XOA_PASSWORD environment variable]" >&2
	echo " -l | –pool MyXenPool1 = Use this pool when looking for the template." >&2
	echo " [Omit to ignore]" >&2
	echo " -x | –no-unregister = Don't log out from the XOA server once connected." >&2
	echo " -d | –debug = Log output to /tmp/xocli_output" >&2
	echo " -d | –debug /path/to/debug = Log output to the specified path" >&2
	echo " –debug=/path/to/debug = Log output to the specified path" >&2
	exit 255
	;;
	-s | –server)
	XOA_URL="${2-}"
	shift
	;;
	-u | –user)
	XOA_USER="${2-}"
	shift
	;;
	-p | –password)
	XOA_PASSWORD="${2-}"
	shift
	;;
	-l | –pool)
	XOA_POOL="${2-}"
	shift
	;;
	-t | –template)
	TEMPLATE="${2-}"
	shift
	;;
	-x | –no-unregister)
	UNREGISTER=0
	;;
	-d | –debug)
	DEBUG=/tmp/xocli_output
	[ -n "${2-}" ] && [ "$(echo "${2-}" | cut -c1)" != "-" ] && DEBUG="${2-}" && shift
	;;
	–debug=*)
	DEBUG="$(echo $1 | sed -E -e 's/^[^=]+=//')"
	;;
	*)
	break
	;;
	esac
	shift
	done
	}
	sign_in() {
	[ -z "$XOA_URL" ] || [ -z "$XOA_USER" ] || [ -z "$XOA_PASSWORD" ] && fail "Missing sign-in details" 1
	log_debug "Logging in"
	if [ -n "$DEBUG" ]
	then
	xo-cli –register –au "$XOA_URL" "$XOA_USER" "$XOA_PASSWORD" 2>&1 | tee -a "$DEBUG" | grep -q 'Successfully' || fail "Login failed" 2
	else
	xo-cli –register –au "$XOA_URL" "$XOA_USER" "$XOA_PASSWORD" 2>&1 | grep -q 'Successfully' || fail "Login failed" 2
	fi
	STATE="signed_in"
	}
	get_pool() {
	[ -z "$XOA_POOL" ] && log_debug "No Pool" && return 0
	log_debug "Getting Pool ID"
	if [ -n "$DEBUG" ]
	then
	POOL_ID="\$pool=$(xo-cli –list-objects type=pool | jq -c -r ".[] | select(.name_label | match(\"${XOA_POOL}\")) | .uuid" | sort | tail -n 1 | tee -a "$DEBUG")"
	else
	POOL_ID="\$pool=$(xo-cli –list-objects type=pool | jq -c -r ".[] | select(.name_label | match(\"${XOA_POOL}\")) | .uuid" | sort | tail -n 1)"
	fi
	[ "$POOL_ID" == "\$pool=" ] && fail "Pool provided but no ID received" 3
	}
	get_template() {
	log_debug "Getting template"
	if [ -n "$DEBUG" ]
	then
	TEMPLATE_IS="$(xo-cli –list-objects type=VM-template "${POOL_ID-}" | jq -c ".[] | select(.name_label | match(\"${TEMPLATE}\")) | .name_label" | sort | tail -n 1 | tee -a "$DEBUG")"
	else
	TEMPLATE_IS="$(xo-cli –list-objects type=VM-template "${POOL_ID-}" | jq -c ".[] | select(.name_label | match(\"${TEMPLATE}\")) | .name_label" | sort | tail -n 1)"
	fi
	[ -z "$TEMPLATE_IS" ] && fail "Could not match this template" 4
	if [ -n "$DEBUG" ]
	then
	echo "{\"is\": ${TEMPLATE_IS}}" | tee -a "$DEBUG"
	else
	echo "{\"is\": ${TEMPLATE_IS}}"
	fi
	}
	[ -n "$(command -v xo-cli)" ] || fail "xo-cli is missing, and is a required dependency for this script. Please install it; \`sudo npm -g install xo-cli\`" 5
	parse_params "$@"
	if [ -n "$DEBUG" ]
	then
	rm -f "$DEBUG"
	log_debug "Invoked: $(date)"
	log_debug "Template: $TEMPLATE"
	log_debug "Pool: $XOA_POOL"
	fi
	sign_in
	get_pool
	get_template

view raw get_xoa_template.sh hosted with ❤ by GitHub

This script is invoked from your terraform like this:

variable "template_name" {
  default     = "SomeLinux-version.iso-"
  description = "A regex, partial or full string to match in the template name"
}

variable "poolname" {
  default = "MyPool"
}

data "external" "get_xoa_template" {
  program = [
    "/bin/bash", "${path.module}/get_xoa_template.sh",
    "--template", var.template_name,
    "--pool", var.poolname
  ]
}

data "xenorchestra_pool" "pool" {
  name_label = var.poolname
}

data "xenorchestra_template" "template" {
  name_label = data.external.get_xoa_template.result.is
  pool_id    = data.xenorchestra_pool.pool.id
}

And that’s how you do it. Oh, and if you need to pin to a specific version? Change the template_name value from the partial or regex version to the full version, like this:

variable "template_name" {
  # This assumes your image was minted at midnight on 1970-01-01
  default     = "SomeLinux-version.iso-19700101000000"
}

Featured image is “Barcelos and Braga-18” by “Graeme Churchard” on Flickr and is released under a CC-BY license.