aries-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "John Ross (JIRA)" <>
Subject [jira] [Commented] (ARIES-1383) Provide option to disable the provisioning of dependencies at install time.
Date Thu, 20 Aug 2015 09:23:45 GMT


John Ross commented on ARIES-1383:

I updated the description as follows.

(1) The custom directive is now called apachearies-provision-dependencies and has the possible
values of "install" and "start".

(2) Added discussion of the multiple parents issue. A simplifying assumption will be that
unscoped subsystems may not override the value of apachearies-provision-dependencies from
the scoped parent within the same region and must fail installation if they do so.

> Provide option to disable the provisioning of dependencies at install time.
> ---------------------------------------------------------------------------
>                 Key: ARIES-1383
>                 URL:
>             Project: Aries
>          Issue Type: Improvement
>          Components: Subsystem
>    Affects Versions: subsystem-2.0.2
>            Reporter: John Ross
>            Assignee: John Ross
> -------------
> The Subsystems specification states that all dependencies of a subsystem must have been
installed in order to attain the INSTALLED state. If required dependencies are not found,
the installation must fail.
> This functionality was described in order to achieve fail-fast functionality. If an environment
cannot support the dependencies of a subsystem, it is rejected right away.
> However, there are deployment situations where it is valuable to delay the installation
of dependencies. For example, you may wish to independently and simultaneously install a suite
of subsystems whose contents have interleaving dependencies. This is currently not possible
because the local repository of one subsystem is not available to others. The resources will
not be available to others until they become part of the System Repository (assuming a compatible
sharing policy) once the INSTALLED state is acquired. In the meantime, the other subsystems
fail installation.
> There are three potential workarounds to this issue, none of which may be acceptable
to a particular Subsystems consumer.
> (1) Provide all content as part of a remote repository. Note that this would require
the Subsystem-Content header to be computed by the subsystem provider and not by the implementation.
> (2) Package all subsystems into a single ESA and make use of parent-child relationships.
> (3) Manage the install order manually. Note that this would not handle the case of circular
> A solution that will allow for the independent and simultaneous installation of multiple
subsystems with interleaving content dependencies, thus giving a deployer more flexibility,
is desirable.
> -----------------------------
> A custom directive is introduced: apachearies-provision-dependencies. The possible values
are "install" and "start", which indicate the time at which dependency provisioning should
occur. The default value is "install" which results in the current behavior. This directive
may be specified as part of the Subsystem-SymbolicName header. A value of "start" indicates
that dependencies should not be provisioned at installation time. Rather, this step will occur
when the subsystem is started.
> A subsystem with apachearies-provision-dependencies:=start will remain in the INSTALLING
state until it is started. This is an indication to administration programs monitoring subsystems
via the service registry that the subsystem has not yet had its dependencies provisioned.
When the subsystem is started, the transition from INSTALLING to INSTALLED will then occur
as it does today. Assuming the provisioning of dependencies succeeds, the subsystem will then
immediately transition into the RESOLVING state and proceed as normal.
> State transitions when apachearies-provision-dependencies:=start:
> 	install() : <void> -> INSTALLING
>                        <void> -> INSTALLING -> INSTALL_FAILED (if installation
fails for some reason other than dependency provisioning)
> 		     INSTALLING -> INSTALLING (if provisioning of dependencies fails)
>                      INSTALLING -> INSTALLED -> RESOLVING -> INSTALLED (if runtime
resolution fails)
RESOLVED (if starting fails)
> Child subsystems inherit the apachearies-provision-dependencies value of the first scoped
ancestor unless explicitly overridden. The root subsystem always has a value of apachearies-provision-dependencies:=install.
> ---------------------------------
> (1) Make the local repositories of installing subsystems available to other installing
subsystems. The specification does not allow local repositories to be registered as a Repository
service, although it does not explicitly address the possibility of a particular implementation
sharing them internally. Nevertheless, the intent of the spec seems clear in that it should
not be assumed that a subsystem provider desires their content to be shared with others.
> -------------------------
> (1) The proposed solution will break the contract of the install methods specified on
the Subsystem and AriesSubsystem interfaces, which require that either the returned subsystem
is in the INSTALLED state or that the installation fails with an exception. However, it is
assumed that the explicit declaration of the apachearies-provision-dependencies directive
with a value of "start" grants the implementation permission to do so. An alternative would
be to return the Subsystem in the INSTALLED state even though none of the dependencies have
been installed. However, this would also violate the specification and may confuse third party
applications monitoring subsystem services via the registry.
> (2) A subsystem may have more than one parent but at most one scoped parent. This means
that additional parents will always be features (or other unscoped subsystems). The question
is how should apachearies-provision-dependencies inheritance work when there are multiple
parents with conflicting values. A simplifying assumption would be that features may not override
the value of the scoped parent. This implies that features should fail installation if they
contain a value of apachearies-provision-dependencies that conflicts with the scoped subsystem
within the same region.

This message was sent by Atlassian JIRA

View raw message