Right now, there are two conflicting requirements in Fedora Modularity that we need to resolve. 1. Once a user has selected a stream, updates should follow that stream and not introduce incompatiblities. Selected streams should not be changed without direct action from the user. 2. So far as possible, Modularity should be invisible to those who don't specifically need it. This means being able to set default streams so that `yum install package` works for module-provided content. Where this becomes an issue is at system-upgrade time (moving from Fedora 30->31 or continuously tracking Rawhide). Because of requirement 1, we cannot automatically move users between streams, but in the case of release upgrades we often want to move to a new default for the distribution. The Modularity WG has generally agreed that we want and need to support behavior of the following use-cases: Use Case 1: On Fedora 30, user Alice runs yum install Foo The package "Foo" is provided by a module "foo" with a default stream "v1.0". Because it's available in a default stream, the package is installed and the module stream "foo:v1.0" is implicitly enabled for the system. Fedora 31 is released. On Fedora 31, the module "foo" has a new default stream "v1.1". When upgrading from Fedora 30 to Fedora 31, Alice expects the package Foo she installed to be upgraded to version 1.1, because that's what would have happened if it was provided as a package from the non-modular repositories. Use Case 2: On Fedora 30, user Bob runs yum enable foo:v1.0 In this case, the "v1.0" stream of the "foo" module has a dependency on the "v2.4" stream of the "bar" module. So when enabling "foo:v1.0", the system also implicitly enables "bar:v2.4". Fedora 31 is released. On Fedora 31, the module stream "foo:v1.0" now depends on "bar:v2.5" instead of "bar:v2.4". The user, caring only about "foo:v1.0" would expect the upgrade to complete, adjusting the dependencies as needed. At Flock and other discussions, we've generally come up with a solution, but it's not yet recorded anywhere. I'm sending it out for wider input, but this is more or less the solution we intend to run with, barring someone finding a severe flaw. Proposed Solution: What happens today is that once the stream is set, it is fixed and unchangeable except by user decision. Through discussions with UX folks, we've more or less come to the decision that the correct behavior is as follows: * The user's "intention" should be recorded at the time of module enablement. Currently, module streams can exist in four states: "available, enabled, disabled, default". We propose that there should be two additional states (names TBD) representing implicit enablement. The state "enabled" would be reserved for any stream that at some point was enabled by name. For example, a user who runs `yum install freeipa:DL1` is making a conscious choice to install the DL1 stream of freeipa. A user who runs `yum install freeipa-client` is instead saying "give me whatever freeipa-client is the default". * The state `dep_enabled` would be set whenever a stream becomes enabled because some other module stream depended on it. This state must be entered only if the previous state was `default` or `available`. (We don't want `enabled` or `disabled` streams being able to transition to this state.) * The state `default_enabled` would be set whenever a stream becomes enabled because a transaction pulled in a package from a default stream, causing it to be enabled. This state must only be entered if the previous state was `default` or `dep_enabled`. We don't want `enabled` or `disabled` to be able to transition to `default_enabled`. If a user requests installation of a package provided by a stream currently in the `dep_enabled` state, that stream should transition to the `default_enabled` state (meaning that now the user would expect it to be treated the same as any other default-enabled stream). * When running `dnf update`, if a module stream's dependency on another module changes to another stream, the transaction should cause that new stream to be enabled (replacing the current stream) if it is in the `dep_enabled` state. When running `dnf update` or `dnf system-upgrade`, if the default stream for a module installed on the system changes and the module's current state is `default_enabled`, then the transaction should cause the new default stream to be enabled. * If stream switching during an update or upgrade would result in other module dependency issues, that MUST be reported and returned to the user. This requires some constraints to be placed on default and dependency changes: * Any stream upgrade such as this must guarantee that any artifacts of the stream that is exposed as "API" MUST support RPM-level package upgrades from any previous stream in this stable release. (Example: "freeipa:DL"1 depends on a the "pki-core:3.8" stream at Fedora 30 launch. Later updates move this to depending on "pki-core:3.9" and even later "pki-core:3.10". In this case the packages from "pki-core:3.10" must have a safe upgrade path from both "pki-core:3.8" and "pki-core:3.9" since we cannot guarantee or force our users to update regularly and they might miss some of the intermediate ones. _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx
