Using Template Modules

Template modules are helper files that perform specific functions that can make your templates more efficient. For example, you can have a module that generates unique names for your resources. Deployment Manager can execute any module written in Python or Jinja.

Before you begin

Creating a template module

A template module is treated as a regular template file and can be written in Jinja or Python.

For example, the following is a helper template that generates a name given a prefix and suffix.

Jinja


In Jinja, this helper template (in this example, named helpers/common.jinja) would look like the following:

{#
Copyright 2016 Google Inc. All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
#}

{%- macro GenerateMachineName(prefix='', suffix='') -%}
    {{ prefix + "-" + suffix }}
{%- endmacro %}

You can then import this template and use it as a module. In your Jinja template, you could use the module like so:

# Copyright 2016 Google Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


{% import 'helpers/common.jinja' as common %}

resources:
- name: {{ common.GenerateMachineName("myfrontend", "prod") }}
  type: compute.v1.instance
  properties:
    zone: us-central1-f
    machineType: https://www.googleapis.com/compute/v1/projects/{{ env['project'] }}/zones/us-central1-f/machineTypes/f1-micro
    disks:
    - deviceName: boot
      type: PERSISTENT
      boot: true
      autoDelete: true
      initializeParams:
        sourceImage: https://www.googleapis.com/compute/v1/projects/debian-cloud/global/images/family/debian-9
    networkInterfaces:
    - network: https://www.googleapis.com/compute/v1/projects/{{ env['project'] }}/global/networks/default
      accessConfigs:
      - name: External NAT
        type: ONE_TO_ONE_NAT

The configuration must then import both files (including the helpers/common.jinja file):

# Copyright 2015 Google Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

imports:
- path: helpers/common.jinja
- path: vm-instance-example.jinja

resources:
- name: my-vm
  type: vm-instance-example.jinja

The Deployment Manager service will expand the configuration and the final configuration looks like this:

resources:
- name: myfrontend-prod
  type: compute.v1.instance
  properties:
    zone: us-central1-f
    machineType: https://www.googleapis.com/compute/v1/projects/myproject/zones/us-central1-f/machineTypes/f1-micro
    disks:
    - deviceName: boot
      type: PERSISTENT
      boot: true
      autoDelete: true
      initializeParams:
        sourceImage: https://www.googleapis.com/compute/v1/projects/debian-cloud/global/images/family/debian-9
    networkInterfaces:
    - network: https://www.googleapis.com/compute/v1/projects/myproject/global/networks/default
      accessConfigs:
      - name: External NAT
        type: ONE_TO_ONE_NAT

Python


In Python, the helper template (in this example, named helpers/common.py) would look like this:

# Copyright 2016 Google Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Generates name of a VM."""


def GenerateMachineName(prefix, suffix):
  return prefix + "-" + suffix

To use it in your Python template:

# Copyright 2016 Google Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Constructs a VM with imported module."""
from helpers import common

COMPUTE_URL_BASE = 'https://www.googleapis.com/compute/v1/'


def GenerateConfig(context):
  """Generates configuration of a VM."""
  resources = [{
      'name': common.GenerateMachineName('myfrontend', 'prod'),
      'type': 'compute.v1.instance',
      'properties': {
          'zone': 'us-central1-f',
          'machineType': COMPUTE_URL_BASE + 'projects/' + context.env['project']
                         + '/zones/us-central1-f/machineTypes/f1-micro',
          'disks': [{
              'deviceName': 'boot',
              'type': 'PERSISTENT',
              'boot': True,
              'autoDelete': True,
              'initializeParams': {
                  'sourceImage': COMPUTE_URL_BASE + 'projects/'
                                 'debian-cloud/global/images/family/debian-9'}
          }],
          'networkInterfaces': [{
              'network': COMPUTE_URL_BASE + 'projects/' + context.env['project']
                         + '/global/networks/default',
              'accessConfigs': [{
                  'name': 'External NAT',
                  'type': 'ONE_TO_ONE_NAT'
              }]
          }]
      }
  }]
  return {'resources': resources}

The configuration must then import both files (including the helpers/common.py file):

# Copyright 2015 Google Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

imports:
- path: helpers/common.py
- path: vm-instance-example.py

resources:
- name: my-vm
  type: vm-instance-example.py

Here is a more complicated helper module:

# Copyright 2015 Google Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Helper methods for working with containers in config."""
import common
import default
import yaml

# Specific properties for this component, also see container_instance
DCKRENV = default.DCKRENV
DCKRIMAGE = default.DCKRIMAGE

MANIFEST = """
version: v1beta2
containers:
  - name: %(name)s
    image: %(dockerImage)s
    ports:
      - name: %(name)s-port
        hostPort: %(port)i
        containerPort: %(port)i
    %(env)s
"""


def GenerateManifest(context):
  """Generates a Container Manifest given a Template context.

  Args:
    context: Template context, which must contain dockerImage and port
        properties, and an optional dockerEnv property.

  Returns:
    A Container Manifest as a YAML string.
  """
  env = ""
  env_list = []
  if DCKRENV in context.properties:
    for key, value in context.properties[DCKRENV].iteritems():
      env_list.append({"name": key, "value": value})
  if env_list:
    env = "env: " + yaml.dump(env_list, default_flow_style=True)

  manifest_yaml_string = MANIFEST % {
      "name": context.env["name"],
      "dockerImage": context.properties[DCKRIMAGE],
      "port": context.properties[default.PORT],
      "env": env
  }
  return common.GenerateEmbeddableYaml(manifest_yaml_string)

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