[V2V] Add default setting for CPU and network limits per conversion host, and max concurrent tasks per EMS

[ghost]

In the current implementation, we are able to control the max number of concurrent conversions per conversion host via the settings. For advanced throttling, we need to add the same for CPU and network limits. We also need the max number of concurrent conversions per EMS, which is today a default value in the throttling code. This PR adds them to config/settings.yml, under transformation / limits.

Associated RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1686169

[ghost]

@miq-bot add_label transformation, enhancement, hammer/yes
@miq-bot add_reviewer @djberg96
@miq-bot add_reviewer @agrare

[djberg96]

Hm, do we need the word "unlimited" there? If we have the key with no value, then I think it's implicit that it's not set, therefore unlimited. Or perhaps even just false.

[ghost]

@djberg96 It's string that we then pass to virt-v2v-wrapper. When discussing with Tomas, he said that he prefers unlimited to clearly state, rather than nil or false. It's more explicit. We could make it a default in the ServiceTemplateTransformationPlanTask, but I thought that keeping it in a single place would be nicer.

[agrare]

@fdupont-redhat I don't see where this is being used, is there another PR that will use this value? I agree with @djberg96 it looks weird to see a string value in what I'd expect to be an integer/float field, and prior to passing to the v2v-wrapper we could do cpu_limit || "unlimited"

[mturley]

@fdupont-redhat I think we need max_concurrent_tasks_per_provider here too (mockups here: https://docs.google.com/presentation/d/1BoMkoClBSxATQRPRYt7zuTgRYjaNCIE0y5xCGv5akL4/edit#slide=id.g3f0eb56eb7_0_1).

[ghost]

@agrare the expected value is a string to accomodate evolution in the format on virt-v2v-wrapper side. Also, we could have had the same kind of default value for max_concurrent_tasks, but it was finally set in Settings: https://github.com/ManageIQ/manageiq/blob/master/app/models/conversion_host.rb#L36.

[ghost]

@mturley good point. I'll add it, because today's implementation based on custom attribute is dirty.

[miq-bot]

Checked commits fabiendupont/manageiq@a05f532~...fd4d5e7 with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
0 files checked, 0 offenses detected
Everything looks fine. 👍

[simaishi]

Hammer backport details:

$ git log -1
commit a1b667b45fbc38ef4a169d16f1fa6a513433c1a8
Author: Adam Grare <agrare@redhat.com>
Date:   Thu Mar 7 11:11:44 2019 -0500

    Merge pull request #18528 from fdupont-redhat/v2v_add_default_throttling_setting_cpu_and_network
    
    [V2V] Add default setting for CPU and network limits per conversion host, and max concurrent tasks per EMS
    
    (cherry picked from commit a921fcfd995c1bda55b54b2d7bc43f1a6176530e)
    
    Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1686874