94 lines
3.5 KiB
Python
94 lines
3.5 KiB
Python
# Copyright 2014-2015 Canonical Limited.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import os
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import sys
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from charmhelpers.core import host
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from charmhelpers.core import hookenv
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def render(source, target, context, owner='root', group='root',
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perms=0o444, templates_dir=None, encoding='UTF-8',
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template_loader=None, config_template=None):
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"""
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Render a template.
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The `source` path, if not absolute, is relative to the `templates_dir`.
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The `target` path should be absolute. It can also be `None`, in which
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case no file will be written.
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The context should be a dict containing the values to be replaced in the
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template.
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config_template may be provided to render from a provided template instead
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of loading from a file.
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The `owner`, `group`, and `perms` options will be passed to `write_file`.
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If omitted, `templates_dir` defaults to the `templates` folder in the charm.
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The rendered template will be written to the file as well as being returned
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as a string.
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Note: Using this requires python-jinja2 or python3-jinja2; if it is not
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installed, calling this will attempt to use charmhelpers.fetch.apt_install
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to install it.
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"""
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try:
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from jinja2 import FileSystemLoader, Environment, exceptions
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except ImportError:
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try:
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from charmhelpers.fetch import apt_install
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except ImportError:
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hookenv.log('Could not import jinja2, and could not import '
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'charmhelpers.fetch to install it',
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level=hookenv.ERROR)
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raise
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if sys.version_info.major == 2:
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apt_install('python-jinja2', fatal=True)
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else:
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apt_install('python3-jinja2', fatal=True)
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from jinja2 import FileSystemLoader, Environment, exceptions
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if template_loader:
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template_env = Environment(loader=template_loader)
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else:
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if templates_dir is None:
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templates_dir = os.path.join(hookenv.charm_dir(), 'templates')
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template_env = Environment(loader=FileSystemLoader(templates_dir))
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# load from a string if provided explicitly
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if config_template is not None:
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template = template_env.from_string(config_template)
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else:
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try:
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source = source
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template = template_env.get_template(source)
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except exceptions.TemplateNotFound as e:
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hookenv.log('Could not load template %s from %s.' %
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(source, templates_dir),
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level=hookenv.ERROR)
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raise e
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content = template.render(context)
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if target is not None:
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target_dir = os.path.dirname(target)
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if not os.path.exists(target_dir):
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# This is a terrible default directory permission, as the file
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# or its siblings will often contain secrets.
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host.mkdir(os.path.dirname(target), owner, group, perms=0o755)
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host.write_file(target, content.encode(encoding), owner, group, perms)
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return content
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