Validate plugin compatibility with version ranges

[hairyhum]

Proposal for #591

In plugin .app.src rabbitmq versions will be defined like {rabbitmq_versions, ["3.5.4", "3.6.0"]}, which means that this plugin valid for versions "3.5.4" and higher "3.5.x" and all "3.6.x" versions.
The same format is used for plugin dependencies e.g:

{application, rabbitmq_federation_management,[
    ...
    {plugins_versions, [{rabbitmq_management, ["3.7.2"]}, {rabbitmq_federation, ["3.7.0"]}]}
]}.

Requires rabbitmq_management dependency version to be 3.7.2 or higher for 3.7.x series and rabbitmq_federation version to be any of 3.7.x series.

[hairyhum]

In plugin .app.src rabbitmq versions will be defined like {rabbitmq_versions, ["3.5.4", "3.6.0"]}, which means that this plugin valid for versions "3.5.4" and higher "3.5.x" and all "3.6.x" versions.

[michaelklishin]

Lets start with some automated test examples that'd demonstrate how it works and what kind of edge cases there may be.

[hairyhum]

Should we continue with this?

[michaelklishin]

@hairyhum I haven't looked at it properly yet, sorry.

[hairyhum]

Maybe it makes sense to include version checks for plugins depending on plugins.

[hairyhum]

Here are possible error messages:

Rabbitmq version mismatch:

[warning] Problem reading some plugins: plugin1: version mismatch, required: ["3.5.0","3.6.0"], got "3.7.0"

Rabbitmq version is not specified:

[warning] Some plugins doesn't specify required RabbitMQ version: plugin2, plugin3

Plugin dependency version do not match: (specified required version for dep1 and dep2, dep1 doesn't exist, dep2 version do not match requirement)

[warning] Some plugin versions do not match:
    plugin1: 
        missing dependency: dep1
        dependency version mismatch: dep2 required ["3.5.6", "3.6.0"], got "3.7.0"

Plugin will not be loaded in case of version mismatch. But will be loaded if required version is not specified. There should be some way to inform about it.

@michaelklishin @dumbbell @bdshroyer any ideas on improving messages?

[michaelklishin]

"Problem loading a plugin…"
"Some plugin do not specify…"

I also don't think that using a pair of two versions will be very clear to the user.

[hairyhum]

Error message format example:

Failed to enable some plugins: 
    rabbitmq_federation_management:
        Dependency is missing or invalid: rabbitmq_management
    rabbitmq_management:
        Broker version is invalid. Current version: "3.7.0" Required: ["3.6.0"]
    rabbitmq_shovel_management:
        rabbitmq_shovel plugin version is invalid. Current version: "3.7.1" Required: ["3.7.2"]    

When running rabbitmq-plugins enable or rabbitmq-plugins set invalid plugins will not be added to enabled_plugins and error is printed.
When plugins (or broker) are updated and server restarts with existing list of plugins - it will print message to log and start without this plugins.

[michaelklishin]

This value is updated at build time. @dumbbell do you agree with this default value bump?

[hairyhum]

Sorry, commited accidentally.

[michaelklishin]

Should we address this?

[michaelklishin]

@hairyhum this is on the finish line but there are still two things to do:

• I had to update the copy. Please check that I haven't made any mistakes.
• When I configure rabbitmq_management to validate rabbitmq_management_agent version so that I can trigger a dependency version mismatch error, I get effective version reported incorrectly.

Specifically, with the following added to rabbitmq_management.app.src:

{dependency_version_requirements, [{rabbitmq_management_agent, ["3.7.0"]}]},

and attempt to start the broker with `make run-broker PLUGINS='rabbitmq_management',
the effective version reports doesn't seem correct:

Error: Failed to enable some plugins:
    rabbitmq_management:
        Version '[]' of dependency 'rabbitmq_management_agent' is unsupported. Version ranges supported by the plugin: ["3.7.0"]

[michaelklishin]

Scratch the above, it's due to the fact that in development plugin version was an empty string. When I set it to a realistic value, I get what I expect:

Error: Failed to enable some plugins:
    rabbitmq_management:
        Version '"3.4.0"' of dependency 'rabbitmq_management_agent' is unsupported. Version ranges supported by the plugin: ["3.7.0"]

So yeah, this seems to be mostly about copy review and a bit more testing, e.g. with a release build.

[hairyhum]

I guess we can skip validations if plugin version is empty, assuming it's development version. Or just warn users that there are empty versions, which won't be checked.

[michaelklishin]

@hairyhum OK, that sounds like a good idea. Since this is in master, we should also add debug logging for what plugins were checked against what version ranges.

[michaelklishin]

We should rename this to dependency_version_mismatch to be more specific.