[wildfly-dev] Updating WildFly instance with the Provisioning Tool

[Emmanuel Hugonnet]

Hey guys,

TL;DR
I've been experimenting with Alexey to update a customized provisioned server using the provisioning tool [1].
I'm using the syncing operations [2] that I created a while back by porting the domain synchronization operations to standalone (to
synchronize standalone instances in a cloud environment).
I'm looking for some feedback on this approach.
Cheers
Emmanuel

[1]: https://github.com/ehsavoie/pm/tree/upgrade-feature-pack
[2]: https://github.com/ehsavoie/wildfly-core/tree/model_diff

----
full version:


  Updating WildFly


    <https://github.com/ehsavoie/pm/blob/upgrade-feature-pack/docs/guide/wildfly/upgrade.adoc#terminology>Terminology

Updating is the process of applying a fix pack that will increment the micro version. There should be no compatiblity issue. Upgrading is
the transition of a minor version, compatiblity should be available but there are a lot more changes.

While the mecanisms discussed here are general, they might need more refinement for an upgrade.


    <https://github.com/ehsavoie/pm/blob/upgrade-feature-pack/docs/guide/wildfly/upgrade.adoc#use-case>Use case

The use case is quite simple: *I have version 1.0.0 installed and i want to update to 1.0.1 but I have locally customized my server and i’d
like to keep those changes*.
We have several local elements to take into account:

  *

    filesystem changes (files added, removed or deleted).

  *

    configuration changes.

The basic idea is to diff the existing instance with a pure new installation of the same version then apply those changes to a new
provisioned version instance for staging.
We can keep it at the basic filesystem approach with some simple merge strategy (theirs, ours).
We can use the plugin to go into more details. For exemple using the model diff between standalone Wildfly instances we can create a cli
script to reconfigure the upgraded instance in a post-installation step.


    <https://github.com/ehsavoie/pm/blob/upgrade-feature-pack/docs/guide/wildfly/upgrade.adoc#diffing-the-filesystem>Diffing the filesystem

The idea is to compare the instance to be upgraded with one instance provisioned with the same feature packs as the one we want to upgrade.
The plugin will provide a list of files or regexp to be excluded.
Each file will be hashed and we compare the hash + the relative path to deduce deleted, modified or added files.
For textual files we can provide a diff (and the means to apply it), but maybe that should be for a later version as some kind of
interaction with the user might be required.


    <https://github.com/ehsavoie/pm/blob/upgrade-feature-pack/docs/guide/wildfly/upgrade.adoc#wildfly-standalone-plugin>WildFly standalone
    plugin

This is a specialization of the upgrading algorithm:

  *

    Filtering out some of the 'unimportant' files (tmp, logs).

  *

    Creating diff of textual files (for example the realm properties) which will be applied (merging strategy à la git).

  *

    Using an embedded standalone it creates a jboss-cli script to reconfigure the server (adding/removing extensions and reconfiguring
    subsystems).

  *

    Deleting files that were removed.

This is done on a staging upgraded instance before being copied over the old instance.
I have added a diff/sync operation in standalone that is quite similar to what happens when a slave HC connects to the DC. Thus I start the
current installation, and connect to it from an embedded server using the initial configuration and diff the models.
This is 'experimental' but it works nicely (I was able to 'upgrade' from the standalone.xml of wildfly-core to the standalone-full.xml of
wildfly).
I’m talking only about the model part, I leave the files to the filesystem 'diffing' but it wiill work with managed deployments are those
are added by the filesystem part and then the deployment reference is added in the model.
For a future version of the tooling/plugin we might look for a way to interract more with the user (for example for applying the textual
diffs to choose what to do per file instead of globally).
Also currently the filters for excluding files are defined by the plugin but we could enrich them from the tooling also.


    <https://github.com/ehsavoie/pm/blob/upgrade-feature-pack/docs/guide/wildfly/upgrade.adoc#producing-an-update-feature-pack>Producing an
    update feature pack

From the initial upgrade mecanism Alexey has seen the potential to create a feature pack instead of my initial format.
Currently i’m able to create and installa a feature-pack that will supersede the initial installation with its own local modifications.
Thus from my customized instance I can produce a feature pack that will allow me to reinstall the same instance. Maybe this can be also use
to produce upgrade feature pack for patching.


    <https://github.com/ehsavoie/pm/blob/upgrade-feature-pack/docs/guide/wildfly/upgrade.adoc#wildfly-domain-mode>WildFly domain mode

Domain mode is a bit more complex, and we need to think how to manager the model changes.
Those can be at the domain level or the host level and depending on the instance target we would need to get the changes from the domain.xml
or/and the host.xml.
I’m thinking about applying the same strategy as what was done for standalone : aka expose the sync operations to an embedded HC.


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