TextRender outside metaconfig

22 September 2015
Stijn De Weirdt

TextRender outside metaconfig

The 3rd part of this series deals with usage of TextRender in e.g. components other than metaconfig or other perl modules.

Altough metaconfig can handle most configuration work where generating a configuration file combined with restarting/reloading/… a sysvinit/systemd service is sufficient, there are still quite a lot of cases where more logic or complicated action is required.

In these cases, a component or perl module is required. This was briefly touched upon in the 1st part introducing TextRender.

This final part will go into more detail how to integrate the convenient way of writing Template::Toolkit (TT) and unittests from metaconfig with regular component development and testing.

metaconfig migration

The main idea is that TT files and unittests can be moved easily to or from metaconfig, if such opportunity or necessity would arise.

This allows for development in 2 directions:

  • towards metaconfig: existing components that could be replaced by ncm-metaconfig, can be migrated to metaconfig-only using an intermediate step by handling the rendering of the configuration file(s) with TextRender in the existing component, and deprecating the component in a later phase. It is even possible to develop metaconfig support in parallel with the existence of the component. All TT files from metaconfig can be used by any component (and the unittesting of these TT files is done as part of metaconfig), but refactoring the schema is then also required.
  • away from metaconfig: starting out with metaconfig can be a considerable effort. However, if the need ever arises, developing a new component can be done by reusing almost all this effort in a transparent way.

Differences with metaconfig development

location and packaging

Create the ncm-mycomponent/src/main/resources directory with the TT files and a tests subdirectory to hold the TT unittest profiles and RegexpTests.

(This directory should not be confused with the src/test/resources directory, which holds e.g. the pan templates for the perl unittests).

pan schema and other templates

The location directory is the equivalent of the ncm-metaconfig/src/main/metaconfig/myservice directory for a ncm-metaconfig service, with the main exception that there is no ncm-mycomponent/src/main/resources/pan subdirectory.

There is no need to create a TT-specific schema, one has to use the components schema (located in e.g. ncm-mycomponent/src/main/pan/component/mycomponent/schema.pan).


In order to package the TT files as part of the component, a 2 build plugins need to be added to the pom.xml under


The configuration of the plugins is

    <mappings combine.children="append">

(The outputDirectory has (part of) the includepath /usr/share/templates/quattor hardcoded; one should never have to change the includepath either in the pom.xml or the perl TextRender->new()).

TT namespace

TT files used outside metaconfig should use their own namespace and this should be the same as their relpath. E.g. to include a TT file from the mycomponent namespace in a main.tt, one has to use

[% INCLUDE 'mycomponent/element.tt` %]

and the relevant TextRender perl code has

my $trd = EDG::WP4::CCM::TextRender->new(
    relpath => 'mycomponent',
    log => $self,

In metaconfig, the relpath is always metaconfig, and the namespace is e.g. metaconfig/myservice, the equivalent of the example above would be

[% INCLUDE 'metaconfig/myservice/element.tt' %]

Error handling

TextRender never logs any error, it is left entirely to the consumer to handle any errors. The failure reason is held in a fail attribute of the TextRender instance.

There are 2 main ways to detect failures ($trd is the TextRender instance):

  • using the get_text method explicitly, which returns undef in case of rendering failure
if(! defined($trd->get_text())) {
    $self->error("Rendering XYZ failed: $trd->{fail}.");
  • using filewriter method (if you are going to write the contents to file). This returns undef in case of rendering failure (and a vaild CAF::FileWriter instance otherwise).
my $fh = $trd->filewriter('/path/to/file');
if(defined($fh)) {
    my $changed = $fh->close();
} else {
    $self->error("Rendering XYZ failed: $trd->{fail}.");

(The defined($fh) is required, do not simply use if($fh) due to stringification of CAF::FileWriter, as explained in the example below).

TT perl unittest

A dedicated test module Test::Quattor::TextRender::Component exists to testing of TT files outside metaconfig. It is advised to add a single perl unittests 01_tt.t under ncm-mycomponent/src/test/perl, with contents

use strict;
use warnings;

use Test::More;
use Test::Quattor::TextRender::Component;

my $t = Test::Quattor::TextRender::Component->new(
    component => 'mycomponent'


This will look into src/main/resources/tests for profiles and RegexpTests.

TextRender unittest profiles

The test profiles in src/main/resources/tests/profiles are compiled with both the template-library-core and the component target/pan directory in the panc include path, which allows you to use e.g. the component schema or other templates in the TT unittest profiles.

RegexpTests flags

An important difference with metaconfig are the RegexpTest flags. Because a metaconfig service specifies the module and contents as part of the schema for each service, a single renderpath flag is sufficient.

Outside metaconfig however, the module to be used is part of the components perl code, and it can be very common that only a part of the full component schema is used for rendering. Therefor the renderpath flag has lost almost (if not all) of its functionality, and is typically just a (mandatory) placeholder flag with value / (because a valid pan path is still required as the renderpath by the test framework).

The module to be used can be set using the rendermodule flag (and it precedes the default <renderpath>/module value). Similar, the contentspath flag defines the contents to use to render (and it precedes the default <renderpath>/contents). The Element instance $config->getElement('<contentspath>') is passed as the contents.

Be aware of subtle differences between the tests that use the Element instance as contents, and the actual component perl code that you might actually pass e.g. $config->getTree($panpath) (which is a perl hashref, and has by default no type information). In general, one should never use getTree contents in TextRender; and always use an Element instance via getElement (or a self constructed perl hashref).

Any element options passed to TextRender in the perl code, also have to be set via the element flag as a comma-separated list.

E.g. the flags for the pan example from the 1st series


component perl unittests

Component perl unittests (other than the 01_tt.t to test the TT files), and that use the rendered text during the test, need to mock TextRender so it is able to find the TT files in the unittest target directory.

Mocking TextRender for this purpose is as trivial as adding

use Test::Quattor::TextRender::Base;
my $caf_trd = mock_textrender();

before the actual testing is setup, i.e. early in the unittest file.

This is required because by default, TextRender looks for TT files relative to the (absolute) includepath /usr/share/templates/quattor, and the unittests would either not find the TT files required to render, or pick up old/existing ones).

(Be aware that including TT from other components, including metaconfig, during the unittests is not trivial, and outside the scope of this document. If you want to achieve this, open an issue in the relevant github repository to get help.)


We will have a look at snippets of ncm-authconfig (based on 15.8 version). This component manages the system authentication services, one of them is SSSD.

SSSD itself has a relative simple configuration, and in case of any changes, restarting the sssd daemon is sufficient. So it could be handled by metaconfig on it’s own, but it is part of authconfig component because it has impact on the whole authentication system. In particular, enabling/disabling SSSD is done with the authconfig tool (which involves a lot more than simply enabling/disabling the sssd daemon).


The following files (relative from the configuration-modules-core base directory) are relevant for this example:

  • the component authconfig.pm itself
  • the TT files and regexptests in ncm-authconfig/src/main/resources
  • the perl TT unittest 01_tt.t
  • a perl unittest configure-sssd.t


The main Configure method has (related to the SSSD configuration itself)


sub Configure
    my ($self, $config) = @_;

    my $t = $config->getElement("/software/components/authconfig")->getTree();


    if ($t->{method}->{sssd}->{enable}) {
        $restart ||= $self->configure_sssd($t->{method}->{sssd});


The ncm-authconfig schema has a boolean for each supported authentication method. If sssd is enabled, the enable_sssd method is called and adds the relevant arguments to the authconfig commandline. Clearly this kind of logic lies outside the scope of metaconfig, and using a dedicated component is the only solution.

(This is legacy code, a better way to get the profile configuration is to use

my $t = $config->getTree($self->prefix());


SSSD configuration generation

use EDG::WP4::CCM::TextRender;
use constant SSSD_FILE => '/etc/sssd/sssd.conf';
use constant SSSD_TT_MODULE => 'sssd';
sub configure_sssd
    my ($self, $config) = @_;

    my $trd = EDG::WP4::CCM::TextRender->new(
            relpath => 'authconfig',
            log => $self,

    # can't be empty string, is at least '[sssd]'
    if ($trd) {
        my $fh = $trd->filewriter(SSSD_FILE, log => $self, mode => 0600);
        my $changed = $fh->close();

        if ($changed) {
            CAF::Process->new([qw(/sbin/service sssd restart)],
                              log => $self)->run();
            if ($?) {
                $self->error("Failed to restart SSSD");

        return $changed;
    } else {
        $self->error("Unable to render template sssd: $trd->{fail}");

In the sssd example, the rendering error is catched via if($trd), which is possible only for 2 reasons:

  • the rendered sssd configfile is never empty (it contains at the very least the [sssd])
  • the TextRender instance has overloaded stringification (i.e. "$trd" is the content of the rendering) and stringification is a fallback for the boolean overload via magic autogeneration. The TextRender stringification always produces a string (even in case of rendering failure). So when perl evaluates the TextRender instance in boolean context (due to the if()), it will look for an overloaded bool first (which doesn’t exist), and then evaluate the boolean value following the fallbacks, of which stringification exists. An empty string is false in boolean context, anything else it true.

(CAF::FileWriter also has auto stringification, and this is why if(defined($fh)) is required to correctly detect rendering errors when using $trd->filewriter.)

(More legacy code:

  • using constant for constants is discouraged, we should switch to Readonly, in which case the code above becomes
use Readonly;


Readonly my $SSSD_FILE => '/etc/sssd/sssd.conf';

    my $fh = $trd->filewriter($SSSD_FILE, log => $self, mode => 0600);

  • the restart should be handled by CAF::Service as follows
            CAF::Service->new(['sssd'], log => $self)->restart();
            if ($?) {
                $self->error("Failed to restart SSSD");


TT files

The configuration of SSSD is in .ini format, but sssd has a finer substructue than what the builtin tiny module allows. This allows for a detailed schema, which requires TT rendering.

The main sssd.tt TT file looks as follows

domains = [% domains.keys.join(',') %]

[% INCLUDE authconfig/generic.tt dict=global list=['services'] bool=["try_inotify"] %]
[% INCLUDE authconfig/generic.tt dict=pam %]
[% INCLUDE authconfig/generic.tt dict=nss bool=["filter_users_in_groups"] %]

[% FOREACH d IN domains.pairs -%]
[domain/[% d.key %]]
[%  FOREACH pair IN d.value.pairs -%]
[%-      SWITCH pair.key -%]
[%-          CASE ['local'] -%]
[%              INCLUDE "authconfig/generic.tt" dict=pair.value bool=["create_homedir", "remove_homedir"] %]
[%-          CASE ['simple'] -%]
[%              INCLUDE "authconfig/generic.tt" dict=pair.value prefix="${pair.key}_"
                                                list=['allow_users','deny_users','allow_groups','deny_groups'] %]
[%-          CASE ['ldap'] -%]
[%              INCLUDE "authconfig/domains/${pair.key}.tt" desc=pair.value %]
[%      END -%]
[%- END -%]
[% INCLUDE authconfig/generic.tt dict=d.value exclude=['ldap','local','simple']
                                 bool=["case_sensitive", "proxy_fast_alias", "enumerate", "cache_credentials"] %]
[%- END %]

(More legacy code: can probably be simplified a lot using e.g. the type information if an element instance is passed).

TT unittests

An example of a RegexpTest looks like

Value based regexp test
^domains = test1$
^config_file_version = 2$
^debug_level = 528$
^reconnection_retries = 3$

The TextRender module is set to sssd. Only the profile information in /software/components/authconfig/method/sssd is relevant and is passed as contentspath.

The corresponding perl unittest 01_tt.t is

use strict;
use warnings;

use Test::More;
use Test::Quattor::TextRender::Component;

my $t = Test::Quattor::TextRender::Component->new(
    component => 'authconfig'


Perl unittests

There is a regular perl unittest to test the logic in configure_sssd method, e.g. test if a the sssd daemon is restarted via CAF::Service.

use NCM::Component::authconfig;
use Test::MockModule;
use Test::Quattor::TextRender::Base;
my $caf_trd = mock_textrender();
my $close_return;
my $mock = Test::MockModule->new("CAF::FileWriter");

$mock->mock("close", sub {
   my ($self) = @_;
   return $close_return;

my $cmp = NCM::Component::authconfig->new("authconfig");

$close_return = 1;
ok($cmp->configure_sssd({}), "First call changes something");
my $fh = get_file($SSSD_FILE);
isa_ok($fh, "CAF::FileWriter", "File was opened");
is(*$fh->{options}->{mode}, 0600, "File has correct permissions");
my $cmd = get_command($RESTART_CMD);
ok($cmd, "Daemon was restarted");
ok(!$cmp->{ERROR}, "No errors reported in basic execution");

set_command_status($RESTART_CMD, 1);
is($cmp->{ERROR}, 1, "Errors reported when the restart fails");
set_command_status($RESTART_CMD, 0);

$close_return = 0;
# Barfs due to no hashref or element instance
is($cmp->{ERROR}, 2, "Error while rendering the template is reported");

These unittests focus on the logic of the method instead of the rendered text:

  • in the first test, the file returns a forced change, and it is checked that this results in a call to the service restart command.
  • the second test mocks a failed service restart, and it is verified that an error is logged in that case.
  • the third test verifies that an error is logged when TextRender fails

A FileWriter instance has a close method, that returns if the file has changed or not. In this unittest, the close method is mocked to return the value of the $close_return variable. This makes it very easy to mimic the behaviour of the component.

Details of the Test::Quattor testsuite are beyond the scope of this document, but following bits help to understand the internals:

  • both CAF::FileWriter and CAF::Process are mocked by the use Test::Quattor call. This results in easy methods to access the created CAF::FileWriter and CAF::Process instances via get_file and get_command, respectively. There also exists methods to set e.g. the exitcode of a CAF::Process instance via set_command_status.
  • the $cmp->{ERRORS} (and similar $cmp->{WARNINGS}) counter exists for any regular component instance, see the Component documentation. It keeps track of the number of times an error was logged. In the test environment however, the Test::Quattor::Component class is used instead of real NCM::Component, and this test class has a counter for each log action (e.g. ->{INFO} keeps track of the number of times an ->info() log action was called). This is a bit confusing and will be streamlined in a new release of the test tools.


  • are link to the Test::Quattor documentation once added to the documentation generation.
  • add link to Component documentation as part of ncm-ncd