AWS tags as DC/OS agent attributes

README.md

We use this service to populate Agent attributes to DC/OS agent nodes during first boot.

This service populates the tags only during first boot and doesn't trigger changes afterwards, since Mesos Agent config change forces the agent to be re-bootstrapped.

mesos-aws-tags

#!/bin/bash

# based on https://github.com/goguardian/mesos-aws-tags

set -eu

export JAVA_HOME=$(dirname $(dirname $(readlink -f $(which java))))
export EC2_HOME=/opt/ec2-api-tools
export PATH=/usr/local/bin:$EC2_HOME/bin:$PATH

# Export these so the handlers can see them
export ATTRIBUTES_DIR="/etc/mesos-slave/attributes"
export ATTRIBUTES_FILE="/var/lib/dcos/mesos-slave-common"
export HANDLER_DIR=/usr/local/lib/tag_handlers

mkdir -p "${ATTRIBUTES_DIR}"
mkdir -p $(dirname "${ATTRIBUTES_FILE}")
rm -f "${ATTRIBUTES_FILE}"

# Generate individual tags in attributes file
# NOTE: The settings in ${ATTRIBUTES_FILE} supersede any variables that are set
#       in /opt/mesosphere/etc/* (see the EnvironmentFile directives in
#       /etc/systemd/system/dcos-mesos-slave[-public].service.
#
#       In practical terms, this means that we are inadvertently removing the
#       public_ip attribute on public agents.
# See http://mesos.apache.org/documentation/latest/attributes-resources

add_attribute()
{
  local key=$(echo "${1}" | sed -e 's/[/><|:&:+ ]/_/g')
  local clean_value=$(echo "${2}" | sed -e 's/[;:]/_/g')
  local prefix=";"

  if [ -z "${clean_value}" ]; then
    echo "WARN: Not adding mesos attribute for tag ${key} with empty value."
    return
  fi

  if [ ! -f "${ATTRIBUTES_FILE}" ]; then prefix="MESOS_ATTRIBUTES="; fi
  echo -n "${prefix}${key}:${clean_value}" >> "${ATTRIBUTES_FILE}"
}

record_tag()
{
  local clean_key=$(echo "${1}" | sed -e 's/[/><|:&:+ ]/_/g')
  local value="${2}"

  echo "Setting ${clean_key} to ${value} in ${ATTRIBUTES_DIR}"
  echo -n "${value}" > "${ATTRIBUTES_DIR}/${clean_key}"
}

# Fetch tags
INSTANCE_ID=$(ec2-metadata -i | cut -d ' ' -f2)
MY_REGION=$(ec2-metadata --availability-zone | sed 's/.$//' | awk '{print $2}')

# Wait for a tag that we know will be set.
role=""
while [ -z "${role}" ]; do
  echo "Waiting for role tag..."
  role=$(ec2-describe-tags \
           --region $MY_REGION \
           --filter "resource-type=instance" \
           --filter "resource-id=${INSTANCE_ID}" \
           --filter "key=role" | cut -f 4)
  if [ -z "${role}" ]; then sleep 5; fi
done

ec2-describe-tags \
  --region $MY_REGION \
  --filter "resource-type=instance" \
  --filter "resource-id=${INSTANCE_ID}" \
  | cut -f4-5 \
  | while IFS='' read key_and_value; do
      # Split the tag name and value using bash substring removal:
      # - remove the first tab and everything after it to get the key
      # - remove the first tab and everything before it to get the value
      key="${key_and_value%%	*}"
      value="${key_and_value#*	}"
      record_tag "${key}" "${value}"
      add_attribute "${key}" "${value}"
    done

# Cap the attributes file with a newline so handlers can fiddle with it
if [ -s "${ATTRIBUTES_FILE}" ]; then
  echo "" >> "${ATTRIBUTES_FILE}"
fi

# Run handlers for any tags that are set
for tag_file in "${ATTRIBUTES_DIR}"/*; do
  key=$(basename "${tag_file}")
  handler="${HANDLER_DIR}/${key,,}"
  if [ -x "${handler}" ]; then
    value=$(cat "${tag_file}")
    echo "Calling ${handler} with \"${value}\""
    "${handler}" "${value}"
  fi
done

mesos-tags.service

[Unit]
Description=set up instance tags for Mesos to find
After=cloud-final.service

[Service]
Type=oneshot
ExecStart=/usr/local/bin/mesos-aws-tags

[Install]
WantedBy=multi-user.target