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A buildout recipe to manage auto-populating portions of shared configuration files that cannot simply overwritten.

Project Description

Introduction

A buildout recipe to manage auto-populating portions of shared configuration files that cannot simply overwritten.

Overview

In complex buildouts, it is often necessary to create configuration files for various services, such as an Apache web server. Where a separate file is used for each instance, or where it is possible to add an independent file to a directory where it will be read and included in the configuration, this is quite straightforward.

But some services have only one file which may need to have entries for multiple applications or require manual editing. In this case generating a file automatically is simply asking for trouble.

This recipe reads a configuration file and inserts the desired configuration between “marker” lines, which are comments in the configuration file. It also adds an optional comment identifying where these lines came from (and telling people not to edit them). Upon update, the section is replaced with the updated configuration and any changes outside the markers are preserved. The section will also be removed if the part is removed.

Example:

# A sample config file
Existing_1 = One
Existing_2 = Two
# START: my-buildout-section
# Text between these lines generated by buildout. Do not remove or edit
custom_1 = ONE
custom_2 = TWO
# END: my-buildout-section
# Manual comment
Manual_3 = Three

Caveats

While the marker format can be customised to accommodate different comment requirements, there are probably all sorts fo things that can trip it up.

The program should run under Python 2.4 and onwards. It has not been tested with Python 3, nor on a Windows platform, although it was written to be portable and platform independent. Feedback, test results, use cases and patches welcomed!

Usage

Simply add this recipe as a part in your buildout, specifying the target confguration file to be modified and the information to add. The marker lines can be customised to accommodate different commenting requirements. By default, a backup of the original configuation file is created before any changes are made,

Supported options

target

Path to the file to be merged (required). If the file does not exist, it will be created unless create is set to False.

section

A block of configuration text to place between the markers. You must specify this or “section-file,” or “section-template.”

section-file

A file to read, whose contents will be placed between the markers. This is useful for more complex configurations. The file will be deleted after use, unless delete-file is set to False. You must specify this or “section,” or “section-template.”

section-template

Set to the name of a section containing definitions for a collective.recipe.template template. The template section need not be added to the list of parts, unless you also want to execute it separately. When invoked, the output file will be overridden and no file will be created. You must specify this or “section,” or “section-file.”

There are a few things to watch out for when using a template:

  • If you are not going to run the part, leave out the recipe definition, or buildout will throw an error;
  • If you aren’t going to run the part, you needn’t specify an output file either. The recipe will supply a dummy one but no output file will be created. If the part will be run, the output file you specify will not be altered;
  • The section defining the configmanager options, not the template options, will be the base section for the template. That is, defining foo in the template section and using ${foo} in the template will fail. Simply use fully qualified placeholders (${section:foo}) in your templates and everything will work properly.

allow-empty-section

Allow a section, section file or the results of a section-template to be empty (after stripping leading and trailing whitespace). If this is the case, the file will be left unchanged (but uninstall will still run on update to remove any existing entries).

Default: False

backup

Install and Update will create a backup which is the complete file name plus the extension .BK0. Uninstall will create a backup with the extension .BK1. We do it this way because of the way buildout calls the install and uninstall routines (and the disconnect between them). This approach ensures that we always have a valid backup, and that the install backup won’t overwrite a freshly created uninstall backup.

Default: True

create

If the target file does not exist, create it and add the defined section as the only contents.

Default: True

uninstall

Remove section from file if part is uninstalled. If the file would be empty after this it is deleted. If backup was originally set to True, A backup will be created (see the note under start-marker for caveats).

Default: True

insert-after

A regex pattern to look for in the target file. If found, the section contents and markers will be inserted directly after this line. The regex uses search, not match, so it will match the pattern anywhere in the line. If whitespace or the location of the pattern in the line is important, structure your regex accordingly. If the pattern is not found, the section will be appended to the end of the file, as usual.on

Default: None

start-marker

A line that marks the beginning of an auto-generated section. It should include a unique name (e.g. the section name) in case multiple sections are added to the same file. You can do this by referencing ${:_buildout_section_name_} in your custom marker definition

Default: # BEGIN - Generated by: ${:_buildout_section_name_}

Note

If you specify uninstall = false and later change the start-marker, the file won’t be updated properly, as we rely on the uninstall routine to remove the previous markers.

end-marker

The text to use for the ending marker line.

Default: # END - Generated by: ${:_buildout_section_name_}

comment

A line that will be added directly after the start marker. If blank, it will be omitted.

Default: # DO NOT EDIT: Text between these lines generated automatically by buildout

delete-file

If true, delete the file specified in section-file after processing.

Default: False

strict

If true, treat all warnings, such as finding a start marker without a matching end marker as errors.

Default: False

Example usage

We’ll start with an existing file and add a section to it.

>>> import os
>>> from shutil import copy
>>> test_path = join(os.path.dirname(__file__), 'testdata')
>>> target_file = join(test_path, 'TEST_FILE.INI')
>>> copy (
...     join(test_path, 'MASTER_TEST_FILE.INI'),
...     target_file
...     )

First we’ll check that our data isn’t in the file:

>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> '# BEGIN' in contents
False

And write out our configuration:

>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... section =
...     four = 4
...     five = 5
... """ % (target_file)
... )
>>> print system(buildout)
Installing...

We should now have a start marker, a comment, our new entries and our existing ones:

>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> '# BEGIN' in contents
True
>>> 'Text between' in contents
True
>>> 'four = 4' in contents
True
>>> '# END' in contents
True
>>> 'one = 1' in contents
True
>>> 'two = 2' in contents
True

We always create a backup before doing anything, unless you explicity set backup = false. See the backup option documentation for details:

>>> backup_file = join(test_path, 'TEST_FILE.INI.BK0')
>>> backup = open(backup_file, 'r')
>>> contents = backup.read()
>>> backup.close()

Our backup has only our original contents:

>>> 'one' in contents
True
>>> 'four' in contents
False

Empty sections aren’t allowed:

>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... section =
... """ % (target_file)
... )
>>> print system(buildout)
While:
    ...

Error:…

If this happens an already modified file won’t be changed:

>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> '# BEGIN' in contents
True
>>> 'four' in contents
True

Unless we explicitly say so:

>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config
...
... [config]
... recipe = whtc.recipe.configmanager
... allow-empty-section = true
... target = %s
... section =
... """ % (target_file)
... )
>>> print system(buildout)
Uninstalling...

And now we see we have the markers but no data:

>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> '# BEGIN' in contents
True
>>> 'one = 1' in contents
True
>>> 'four = 4' in contents
False

Now let’s change our section contents slightly and update our file

>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... section =
...     four = 4
...     six = 6
... """ % (target_file)
... )
>>> print system(buildout)
Uninstalling...

We should now have everything we had before, but with ‘five = 5’ replaced by ‘six = 6’:

>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> '# BEGIN' in contents
True
>>> 'Text between' in contents
True
>>> 'four = 4' in contents
True
>>> 'five' in contents
False
>>> 'six = 6' in contents
True
>>> '# END' in contents
True
>>> 'one = 1' in contents
True
>>> 'two = 2' in contents
True

We can also supply custom section markers:

>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... start-marker = /*START: ${:_buildout_section_name_}*/
... end-marker = /*FINISH: ${:_buildout_section_name_}*/
... comment =
... section =
...     four = 4
...     nine = 9
... """ % (target_file)
... )
>>> print system(buildout)
Uninstalling...

And we see our markers have changed

>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> '# BEGIN' in contents
False
>>> '# END' in contents
False
>>> '/*START: config*/' in contents
True
>>> '/*FINISH: config*/' in contents
True

We can also look for a specific point to insert our contents:

>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... start-marker = /*START: ${:_buildout_section_name_}*/
... end-marker = /*FINISH: ${:_buildout_section_name_}*/
... comment =
... insert-after = two.*=.*
... section =
...     four = 4
...     nine = 9
... """ % (target_file)
... )
>>> print system(buildout)
Uninstalling...
And now our section comes after two = 2 and before three = 3`:
>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> two_index = contents.find('two =')
>>> three_index = contents.find('three =')
>>> four_index = contents.find('four =')
>>> two_index < three_index
True
>>> three_index > four_index
True

Our section contents can come from a file:

>>> section_file = join(test_path, 'SECTION_FILE.TXT')
>>> copy (
...     join(test_path, 'MASTER_SECTION_FILE.TXT'),
...     section_file
...     )
>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... start-marker = /*BEGIN: ${:_buildout_section_name_}*/
... end-marker = /*FINISH: ${:_buildout_section_name_}*/
... comment =
... section-file = %s
... """ % (target_file, section_file)
... )
>>> print system(buildout)
Uninstalling...
And our file now contains the settings from the input file:
>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> '# six' in contents
False
>>> 'seven = 7' in contents
True
>>> '// This' in contents
True

Our input file can be deleted after use if we wish:

>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... start-marker = /*BEGIN: ${:_buildout_section_name_}*/
... end-marker = /*FINISH: ${:_buildout_section_name_}*/
... comment =
... section-file = %s
... delete-file = true
... """ % (target_file, section_file)
... )
>>> print system(buildout)
Uninstalling...
>>> os.stat(section_file)
Traceback (most recent call last):
    ...
OSError: ...

We can also use a template generated by collective.recipe.template. Note that we don’t add the template section to the parts, as we aren’t installing it on its own. If you did also want to generate an output file with the template part, you could certainly do so. You also don’t need to specify output or recipe; we do here simply to show that no output file will be created:

>>> output_file = join(test_path, 'OUTPUT.TXT')
>>> template_file = join(test_path, 'TEMPLATE.IN')
>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config
...
... [template]
... input = %s
... output = %s
... nine-var = 9
... ten-var = 10
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... start-marker = /*BEGIN: ${:_buildout_section_name_}*/
... end-marker = /*FINISH: ${:_buildout_section_name_}*/
... comment =
... section-template = template
... """ % (template_file, output_file, target_file)
... )
>>> print system(buildout)
Uninstalling...

And our file now contains the settings from the template with the variables inserted:

>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> '# seven' in contents
False
>>> 'nine = 9' in contents
True
>>> '// Test template' in contents
True

And a template output file was not created:

>>> os.stat(output_file)
Traceback (most recent call last):
    ...
OSError: ...

But if we want, we can run the template part as well, and a file will be created:

>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config template
...
... [template]
... recipe = collective.recipe.template
... input = %s
... output = %s
... nine-var = 9
... ten-var = 10
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... start-marker = /*BEGIN: ${:_buildout_section_name_}*/
... end-marker = /*FINISH: ${:_buildout_section_name_}*/
... comment = // This is new
... section-template = template
... """ % (template_file, output_file, target_file)
... )
>>> print system(buildout)
Uninstalling...

The output file exists:

>>> test = os.stat(output_file)

And our section was updated:

>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> '// This is new' in contents
True

We don’t have to have an input file to read from. If the file doesn’t exist, we will create it (unless you specify create = false):

>>> os.remove(target_file)
>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts = config
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... start-marker = /*BEGIN: ${:_buildout_section_name_}*/
... end-marker = /*FINISH: ${:_buildout_section_name_}*/
... comment =
... section =
...     ten = 10
...     eleven = 11
... """ % (target_file)
... )
>>> print system(buildout)
Uninstalling...

Our file has our data, but nothing else:

>>> target = open(target_file, 'r')
>>> contents = target.read()
>>> target.close()
>>> 'one' in contents
False
>>> 'ten' in contents
True

Finally, our section will be removed if the part is uninstalled. If the result would be an empty file, the file will be removed. Just for fun we’ll change the marker definitions, to show that uninstall will still work:

>>> os.remove(target_file)
>>> write(
... 'buildout.cfg',
... """
... [buildout]
... newest = false
... parts =
...
... [config]
... recipe = whtc.recipe.configmanager
... target = %s
... start-marker = //BEGIN: ${:_buildout_section_name_}
... end-marker = //FINISH: ${:_buildout_section_name_}
... comment =
... section =
...     ten = 10
...     eleven = 11
... """ % (target_file)
... )
>>> print system(buildout)
Uninstalling...

The file is gone:

>>> os.stat(target_file)
Traceback (most recent call last):
    ...
OSError: ...
But a backup (.BK1) was created, because backup = true by default:
>>> backup_file = join(test_path, 'TEST_FILE.INI.BK1')
>>> backup = open(backup_file, 'r')
>>> contents = backup.read()
>>> backup.close()
>>> print contents
# Test file...

Change History

1.0rc1

  • Initial public release.
Release History

Release History

This version
History Node

1.0rc1

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