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V4/Server Upgrade Refactoring

Revision as of 10:27, 13 October 2015 by Alich (talk | contribs)
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Name: V4/Server Upgrade Refactoring
Tickets: #4904 , #4834 , #3560 , #3351 , #3849
Target version: 4.2.0
Author: Mbasti
Incomplete.png Pending review
Last updated: 2015-10-13 by Alich

Overview

FreeIPA server becomes full of new features and enhancements over the time, which makes upgrade process hard to keep in shape.

Following improvements, listed in this design, should make server update process more deterministic, robust and working well in various update environments (%posttrans update, containers, etc.).

Use Cases

  • Make update process more deterministic
  • Merge server update commands into the one command (ipa-server-upgrade)
  • Solve upgrades in containers
  • Prevent to run IPA service, if code version and configuration version does not match
    • ipactl should execute ipa-server-upgrade if needed
  • Prevent user to use ipa-upgradeconfig and ipa-ldap-updater
    • remove ipa-upgradeconfig
    • refactor ipa-ldap-updater to allow execute updates for specified files with HUGE warning (disallow to execute overall update)

Design

Make upgrade process more deterministic

Freeipa-devel list discussion

Currently update process do several optimizations which may prevent some errors during update (do update in proper relation parent to children, respectively children to parent during removing). In other hand, the parent to child relation, is not the only one restriction. We use several plugins in 389 directory server, which require proper order of updates in different sub trees.

It causes unexpected errors because the order of updates in files is not the same as real update. Developers should be responsible for proper order of updates, as is not possible to create effective updates sorting, which will respect all 389 DS plugins requirements.

This effort consist of following steps:

  • Do not sort order of updates based on length of DN.
  • Do not use dictionary to store updates. Dictionary mixes the order of particular updates per file. Using lists achieve, the order of updates will be same as order in files.
  • Apply updates per file, in specified order from top to bottom.

Ordering LDAP updates

All LDAP update files are ordered/executed in alphabetical order. Update files should keep the number prefix, but this is not required anymore by updater.

05-pre-update-plugins.update
10-config.update
20-syncrepl.update
...
90-last.update
ZZ.update  # this will work, but we should avoid of using number less update files

plugin - the new update file directive

Plugins are called from update files, using new directive plugin:<plugin-name>

Plugins which edits ldap data directly, without using modlists, should be in separate files.

Update plugins modifications

Execution order of plugins is specified in .update files. There is no need to keep PRE_UPDATE and POST_UPDATE plugin classes and FIRST, MIDDLE, LAST order specifications.

Class Updater is used for all update plugins instead of PreUpdate and Postupdate classes.

The execute method of the class, returns only 2 values (restart_ds, modlist)

  • restart_ds - boolean value, DS server will be restarted after modlist application
  • modlist - list of required changes

Merge server update commands into the one command

Related ticket: #4834, #3351

Currently two commands exist, which have to be exucuted in proper order to upgrade IPA:

ipa-ldap-updater --upgrade
ipa-upgradeconfig

Using these commands in wrong order, or execute ipa-upgradecofig if ipa-ldap-updater failed, can break the system.

To resolve issues mentioned above only one command should do upgrade: ipa-server-upgrade.

ipa-server-upgrade characteristics

  • LDAPI only is used for upgrade (no binding using DM password)
  • check the version of configuration and code version, run only if installed version is newer than configuration version (--skip-version-check overrides this check, see steps).
  • upgrade steps:
  1. stop IPA services
  2. check build and installed platform, if platform mismatch abort upgrade
  3. check build version and installed version
    1. newer build than data: continue
    2. same version of data and build: skip data upgrade
    3. older version of build: abort upgrade
  4. prepare DS to upgrade (stop DS, save configuration, disabling listeners, start DS)
  5. SCHEMA update
  6. LDAP data update + update plugins (update of user data in LDAP, and cn=config LDAP configurations)
  7. upgrade configuration (upgrade of services: httpd, named, etc...)
  8. restore DS (stop DS, restoring configuration)
  9. (re)start IPA services
  • update configuration version, if update was successful
  • only former --upgrade/offline method is supported

Prevent to run IPA if version mismatch

Related ticket: #3849

ipactl {start|restart}

  1. compare build platform and platform from the last upgrade/installation (based on ipaplatform file)
    1. if platform mismatch, raise error and prevent to start IPA services
  2. compare version of LDAP data(+schema included) and build version (VENDOR_VERSION will be used)
    1. if LDAP data version > build version: raise error and prevent services to start (newer data than IPA build)
    2. if LDAP data version < build version: upgrade required (data are older than IPA build)
    3. if LDAP data version == build version: continue (data up to date)
  3. check if any of services requires upgrade**
    1. if any service requires upgrade, upgrade is required
    2. if any service raises an error about wrong configuration (which requires manual fix by user), raise error and prevent to start services
  4. if any upgrade is required, prevent to start services and prompt user to run ipa-server-upgrade (ipactl will not execute upgrade itself)
  5. (otherwise) start services

** will be available after installers refactoring

This behavior is required in container environments (or fedup), where the ipa-server-upgrade can not be executed as RPM %postrans operation, but data and configuration must be updated before first start of newer IPA.

ipactl start|restart option --skip-version-check overrides this check.

Refactor ipa-upgradeconfig into modules/plugins used by ipa-server-update

This will be done during the installer refactoring.

Requirements for using updates in containers

  • Upgrade must run before first start of IPA services (if required)
  • Switching between images based on different OS distribution is not supported, upgrade can't handle differences in distribution patches.
    • ipactl start | restart refuse to start IPA services if ipaplatform doesn't match the platform in configuration
    • ipa-server-upgrade refuse to start upgrading if ipaplatform doesn't match the platform in configuration
    • --skip-version-check option allows to override this check, but there is no guarantee the IPA will work as expected

Implementation

Storing configuration version and platform (place, format)

The ipapython.version.IPA_VENDOR_VERSION variable is used to determine IPA version. The format is 4.1.2-0.fc21.

The platform value consist of ipaplatform file name which is used for a build. The platform name is detected during first run of ipa-server-upgrade on existing systems, respectively during installation IPA 4.2+ servers.

Values are stored into sysupgrade.state file as ipa_version and ipa_platform

Feature Management

UI

N/A

CLI

Command Options
ipa-server-upgrade
--skip-version-check do not check IPA version
--version show program's version number and exit
-h, --help show this help message and exit
-d, --debug print debugging information
-q, --quiet output only errors
--log-file=FILE log to the given file

Configuration

N/A

How to Test

Run ipa-server-update on various old versions of IPA.

Test Plan

Test Plan

Author

Martin Basti