Transcript WP4-install: LCFG components for EDG

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How to write LCFGng components for
EDG
10/2002
[email protected]
German Cancio – WP4-install LCFG HOW-TO - n° 1
Overview
•LCFG – short reminder
Slides stolen from Enrico and Massimo / INFN
•Writing LCFGng Components for EDG usage
•Examples
•Documentation and links
German Cancio – WP4-install LCFG HOW-TO - n° 2
LCFG – short reminder
German Cancio – WP4-install LCFG HOW-TO - n° 3
WP4 & LCFG
 LCFG
is originally developed by the Computer Science Department
of Edinburgh University
 Handles
automated installation, configuration and management of
machines
 Basic
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

features:
automatic installation of O.S.
installation/upgrade/removal of all (rpm-based) software packages
centralized configuration and management of machines
extendible to configure and manage custom application software
German Cancio – WP4-install LCFG HOW-TO - n° 4
LCFG diagram
Config files
LCFG Config Files
/etc/shadow
/etc/services
+inet.services
Make XML
Profile
sshd
Read telnet login ftp
Load
ALLOWED_NETWORKS
rdxprof
ldxprof
HTTP +inet.allow_telnet
Profile
Profile
+inet.allow_login
+inet.allow_ftp
<inet>
....
in.ftpd : 192.168., 192.135.30.
sshd : ALL
Server
Abstract configuration
parameters for all nodes
stored in a central
repository
ALLOWED_NETWORKS
ALLOWED_NETWORKS
Profile
Generic
+inet.allow_sshd
ALL
<allow
cfg:template="allow_$
tag_$
daemon_$">
Object
Component
Web Server
mickey:x:999:20::/home/Mickey:/bin/tcsh
in.rlogind : 192.168., 192.135.30.XML Profile
....
in.telnetd : 192.168., 192.135.30.
XML profiles
+inet.allow
/etc/group
/etc/inetd.conf
/etc/passwd
/etc/hosts.allow
telnet login ftp
+inet.daemon_sshd
yes
<allow_RECORD
cfg:name="telnet">
.....
<allow>192.168., 192.135.30.</allow>
Local cache myckey
+auth.users
</allow_RECORD>
inet auth
+auth.userhome_mickey
.....
/home/mickey
LCFG Objects
+auth.usershell_mickey
</auth>
/bin/tcsh
Client nodes
<user_RECORD cfg:name="mickey">
<userhome>/home/MickeyMouseHome</userhome>
<usershell>/bin/tcsh</usershell>
A collection
</user_RECORD>
of agents read
configuration parameters and either
generate traditional config files or
directly manipulate various services
German Cancio – WP4-install LCFG HOW-TO - n° 5
LCFG configuration (I)
 Most
of the configuration data are common for a category of nodes
(e.g. diskservers, computing nodes) and only a few are node-specific
(e.g. hostname, IP-address)
 Using
the cpp preprocessor it is possible to build a hierarchical
structure of config files containing directives like #define,
#include, #ifdef, comments with /* */, etc...
 The
configuration of a typical LCFG node looks like this:
#define HOSTNAME pc239
/* Host specific definitions */
#include "site.h"
/* Site specific definitions */
#include "linuxdef.h"
/* Common linux resources */
#include "client.h"
/* LCFG client specific resources */
German Cancio – WP4-install LCFG HOW-TO - n° 6
LCFG configuration (II)
From "site.h"
#define LCFGSRV
grid01
#define URL_SERVER_CONFIG
http://grid01/lcfg
#define LOCALDOMAIN
.lnl.infn.it
#define DEFAULT_NAMESERVERS
192.135.30.245
[...]
From "linuxdef.h"
update.interfaces
eth0
update.hostname_eth0
HOSTNAME
update.netmask_eth0
NETMASK
[...]
From "client.h"
update.disks
hda
update.partitions_hda
hda1 hda2
update.pdetails_hda1
free /
update.pdetails_hda2
128 swap
auth.users
mickey
auth.usercomment_mickey
Mickey Mouse
auth.userhome_mickey
/home/Mickey
[...]
German Cancio – WP4-install LCFG HOW-TO - n° 7
LCFG: configuration changes
 Server-side:
when the config files are modified, a tool (mkxprof)
recreates the new xml profile for all the nodes affected by the
changes
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this can be done manually or with a daemon periodically checking for
config changes and calling mkxprof
mkxprof can notify via UDP the nodes affected by the changes
 Client-side:
the server


another tool (rdxprof) downloads the new profile from
usually activated by an LCFG component at boot
can be configured to work as

daemon periodically polling the server

daemon waiting for notifications

started by cron at predefined times
German Cancio – WP4-install LCFG HOW-TO - n° 8
LCFGng components for EDG usage
German Cancio – WP4-install LCFG HOW-TO - n° 9
LCFG: what’s a component?

Component == object

It's a Perl script (also shell scripts accepted for historic reasons)
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We recommend to phase out shell components.
A backwards compatibility module allows to import old-style components without
any modifications.
Each component provides a Configure() method invoked on startup or
when configuration changes
A simple and typical component behaviour:
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Started when notified of a configuration change
Loads its configuration (locally cached)
Configures the appropriate services, by translating config parameters into a
traditional config file and reloading a service if necessary (e.g. restarting a
init.d service).
German Cancio – WP4-install LCFG HOW-TO - n° 10
LCFG: custom components
 LCFG
provides components to manage the configuration of services
of a machine: inet, auth, nfs, cron, ...
 Admins
can build new custom components to configure and manage
their own applications:

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
define your custom “resources” (configuration parameters)
Write a script containing standard methods with your custom code.
Include in your script a generic library, which contains the definition of
common function used by all components (config loading, log, output, ...)
 For
simple components usually just a few lines of code
German Cancio – WP4-install LCFG HOW-TO - n° 11
Writing LCFG components for EDG
 Software
written for EDG should be portable to whatever farm
management system is used.
 It
is therefore recommended to use whenever possible, standard
SysV procedures for managing services: init.d scripts and
chkconfig.
 LCFG
should not be used for replacing existing SysV init.d
functionality!
 LCFG
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should be used for
retrieving configuration information from the CDB and recreate local
config files
Restarting services if needed via init.d scripts (restart/reload)
Enabling/disabling SysV services to match the configuration DB’s
contents (using chkconfig)
German Cancio – WP4-install LCFG HOW-TO - n° 12
LCFG component methods for EDG
Only method to implement:
 Configure():
processes.
 Methods

Reconfigures the service and notifies running
not recommended for EDG, but available in LCFGng:
Start(), Stop(), Run(), Suspend(), Resume()
German Cancio – WP4-install LCFG HOW-TO - n° 13
EDG / LCFG component template (I)
#!/usr/bin/perl -w
package LCFG::MyComp;
@ISA = qw(LCFG::Component);
use strict;
use LCFG::Component;
use LCFG::Config; # EDG specific
sub Configure($$@) {
my ($self,$res) = @_;
my $config=LCFG::Config->new($res);
my $age=$config->getValue('/persons/John/age');
$self->Fail( "too young") unless ($age>18);
}
new LCFG::MyComp() -> Dispatch();
German Cancio – WP4-install LCFG HOW-TO - n° 14
LCFG component template (II)
 Configure()
method:
# Do the configuration
sub Configure($$@) {
my ($self,$res) = @_;
my $config=LCFG::Config->new($res);
# do whatever is neccesary to reconfigure your service
}
German Cancio – WP4-install LCFG HOW-TO - n° 15
LCFG component template (IV)

The specific part in the configure() method will usually contain three steps:
1. Access my resources via a special API (NVA API – next slide)
my $config=NVA::Config->new();
my $arch=$config->getValue('/system/architecture’);
$self->Fail (“not supported") unless ($arch eq ‘i386’);
2. Generate (or update) config file
open (MYCONFIG,’/etc/myconfig’); …
close(MYCONFIG)
3. Reload/restart a service if neccessary
if ($changed) {
system(‘/sbin/service myservice reload’); …
}
German Cancio – WP4-install LCFG HOW-TO - n° 16
NVA API configuration access library
(EDG only) New component configuration access library
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This library allows true hierarchical configuration structure access on the client
side
Implements a subset of the Node View Access API (v.1)
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
http://cern.ch/hep-proj-grid-fabric-config/documents/nva
Implemented only for Perl components.
Most popular methods:
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$value=$config->getValue (‘/my/path/in/config’);
#access value
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$element=$config->getElement($path);
#configuration element

while ($element->isNextElement()) {
my $newel=$element->getNextElement();
# iterations over element lists
German Cancio – WP4-install LCFG HOW-TO - n° 17
EDG relevant built-in standard functions
 $self->Fail(@array):
prints out a [FAIL] message and exits
 $self->Warn(@array):
prints out [WARNING] message
 $self->OK(@array):
prints out [OK] message
 $self->LogMessage(@array):
Adds message to logfile
(see also the LCFG/Component.pm file)
German Cancio – WP4-install LCFG HOW-TO - n° 18
Configuration information (I)
Configuration information is stored on the LCFG server in two types of
files:
1. The resource definition files (.def)
2. The normal .h & machine configuration files.
German Cancio – WP4-install LCFG HOW-TO - n° 19
Configuration information (II)
1. The .def files contain default resource information:
mycomp.def
/* EDG LCFG mycomponent: default resources */
/* schema version always=1 */
schema
1
/* defined resources and defaults */
myconfig1
myconfig2
defaultvalue2
German Cancio – WP4-install LCFG HOW-TO - n° 20
Configuration information (III)
2. The normal .h & machine config files, where the default configuration is
enhanced/overwritten:
mycomponent.<resource>
<value>
mycomp.myconfig1
whatevervalue
mycomp.myconfig2
whateverothervalue
Some special resources have to be declared for including a component to be
deployed:
# add to profile (always needed)
EXTRA(profile.components)
mycomp
# define XML profile version (always set to 1)
profile.version_mycomp
1
# start on boot time (if required)
EXTRA(boot.services)
mycomp
German Cancio – WP4-install LCFG HOW-TO - n° 21
Hierarchical configurations (I)
 Sometimes,
key-value pairs are not sufficient for the required
configurations.

For example: arrays or lists
 LCFG
has a complex server side mechanism for mapping hierarchical
structures into key-value pairs…
 Table
with person names, ages, and phone numbers (.def file)
@persons age_$ phone_$
persons
age_$
phone_$
German Cancio – WP4-install LCFG HOW-TO - n° 22
Hierarchical configurations (II)
Now we want to add the following to the node config:

John, 35, 12346 and Phil, 21, 54321
The node config file will look like:
mycomp.persons
John Phil
mycomp.age_John
35
mycomp.phone_John
12346
mycomp.age_Phil
21
mycomp.phone_Phil
54321
The /persons/John/age, /persons/John/phone, /persons/Phil/age,
/persons/Phil/phone resources will be accessible to the client via the
NVA API.
German Cancio – WP4-install LCFG HOW-TO - n° 23
Hierarchical configurations (III)
The component accessing the info needs to do:
my $personlist=$config->getElement(‘/persons’);
while($personlist->isNextElement()) {
my $person=$personlist->getNextElement();
my $phone=$config->getElement(‘/persons/’.$person.’/phone’);
my $age=$config->getElement(‘/persons/’.$person.’/age’);
print CONFIG “name: $i – age: $age – phone: $phone\n”;
}
German Cancio – WP4-install LCFG HOW-TO - n° 24
Hierarchical Configurations (IV)
 Note
that there is no limit in the nesting of resources (lists of lists
are possible as well as lists of lists of lists)
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
There are some examples (eg. demo NVA API component)
However it is complex using the mkxprof language. Release 3
developments will include integration with the ‘pan’ HLDL language.
German Cancio – WP4-install LCFG HOW-TO - n° 25
Some tips

Avoid dumping configuration files literally into the database
@configlines
configline_$
configlines
01 02 03 04 05 …
configline_01
FARM=MOOH_BAR
configline_02
MILK_NODE=COW_001
...

This leads to some problems, eg. when you overwrite values for host specific
values

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Rather use a template configuration file shipped with the component RPM
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How do you know that configline_324 is still the line you wanted to change?
Substitute relevant entries in the template cf file
Use the built-in template processor for this (see next slide).
Keep explicit configuration information in the LCFG config files.
German Cancio – WP4-install LCFG HOW-TO - n° 26
Template processor

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A template substitution processor allows for fast generation of config files
Special marked entries allow to substitute specific entries by LCFGng
resources.
Example template file for resources in red:
#
# Myconfig configuration file
#
# directory where database management files are stored
databaseDirectory = <%databaseDirectory%>
# directory where temporary files are stored
tmpDataDirectory = <%tmpDataDirectory%>
# directory where lock files are stored
lockDirectory = <%lockDirectory%>

The template processor is called using
LCFG::Template::Substitute
( ‘/mypath/templatefile',
‘/mypath/myconfigfile', $fake, $res );
German Cancio – WP4-install LCFG HOW-TO - n° 27
Example (I)
Edg-lcfg-syslog – configures /etc/syslog.conf
.def file:
@additions add_$
Additions
add_$
Resources defined on server:
syslog.additions
monitoring kernel
syslog.add_monitoring
local3.*
|/var/obj/tmp/monitor.fifo
syslog.add_kernel
kern.*
/var/log/kernel.log
German Cancio – WP4-install LCFG HOW-TO - n° 28
Example (II)
Component: Configure() method. First part: template generation
sub Configure($$@) {
my ($self,$res,@args)=@_;
my $config=LCFG::Config->new($res);
my $syslogconf='/etc/syslog.conf';
my $status = LCFG::Template::Substitute
( '/usr/lib/lcfg/conf/syslog/template',
'/var/obj/conf/syslog/config', 0, $res );
unless (defined($status)) {
$self->LogMessage($@);
$self->Fail( "failed to create config file (see logfile)");
}
German Cancio – WP4-install LCFG HOW-TO - n° 29
Example (III)
Component: Configure() method. Second part: add missing resources
# extra values from 'additions', using NVA API
my $additions=$config->getElement('/additions');
my @add_array=();
while ($additions->isNextElement()) {
my $add=$additions->getNextElement();
my $add_el=$config->getElement('/additions/'.$add.'/add');
push(@add_array,$add_el->getValue());
}
if (scalar (@add_array)) {
open (CFG, '>>/var/obj/conf/syslog/config') ||
$self->Fail('cannot open config file (see logfile)');
print CFG join("\n",@add_array)."\n";
close (CFG) ||
$self->Fail('cannot close config file (see logfile)');
}
German Cancio – WP4-install LCFG HOW-TO - n° 30
Example (IV)
Component: Configure() method. Third part: copy config file, restart service
# copy over to definitive location if files are different
if (system("/usr/bin/cmp -s $syslogconf /var/obj/conf/syslog/config")){
$self->LogMessage("updating config file");
system('cp -f '.$syslogconf.' '.$syslogconf.'.old');
system('cp -f /var/obj/conf/syslog/config '.$syslogconf)
&& $self->Fail("copying template to $syslogconf: ". $?);
# restart service
if (system('/sbin/service syslog restart')) {
$self->Fail('init.d syslog restart failed: '. $?);
}
}
return 1; #OK
}
German Cancio – WP4-install LCFG HOW-TO - n° 31
Packaging components

In order to generate components in RPM, SRPM, and tar format, the
component has to be packaged according to some guidelines.


Read the COMPONENTS-HOWTO for details and links
If you want to test/develop/package your components without CVS access,
you should copy the following from fabric_mgt/edg-lcfg:


Makefile
edg-lcfg-config directory

Create a directory below the makefile, called edg-lcfg-<name>

Populate it with the following files (take eg. edg-lcfg-syslog as template)



CHANGES, ChangeLog, LICENSE, MAINTAINER, Makefile, README,
README.BUILD, config.mk, specfile, <name>.cin, <name>.def.cin,
<name>.pod.cin
Use the make ‘devpack’ and ‘devrpm’ targets for generating the tar and RPM
packages, respectively.
Once your package is ready, contact WP4 for getting it added to CVS.
German Cancio – WP4-install LCFG HOW-TO - n° 32
Documentation and links
 LCFGng
‘out of the box’: http://www.lcfg.org
 EDG
components and extensions: Check on the EDG CVS repository,
http://datagrid.in2p3.fr -> fabric_mgt/edg-lcfg
 EDG


configuration access API (NVA API v1.0):
http://cern.ch/hep-proj-grid-fabric-config/documents/nva
edg-lcfg-nvaapi library module at the EDG CVS repository
 Documentation

(HOW-TO):
http://datagrid.in2p3.fr/cgi-bin/cvsweb.cgi/fabric_mgt/edglcfg/COMPONENTS-HOWTO
 WP4-install
homepage: http://cern.ch/wp4-install
German Cancio – WP4-install LCFG HOW-TO - n° 33