Sequential API requests in volume list as a bottleneck

[Mateusz Kowalski]

https://bugs.launchpad.net/horizon/+bug/1442310 indicates Nova API not allowing to pass list of instance ids in order to receive only data necessary for Horizon and reduce any overhead

As long as Nova is not patched to allow this, from Horizon side _get_attached_instance_ids and _get_instances can be parallelized. Also volume_ids_with_snapshots can be run in parallel with the other ones.

Apart from this, as Nova API calls Glance to map each instance with corresponding image which is definitely not needed for assignment between volume and instance, we can forge image.name to be empty for each instance in Volumes view. This further reduces time required for the whole view to render.

This has significant impact in the following case
* environment with a lot of instances
* environment with instances boot from image which is not available anymore (as in this case Nova calls Glance for each(!) instance separately)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/426493

[OpenStack Infra (hudson-openstack)]

Change abandoned by Ivan Kolodyazhny (<email address hidden>) on branch: master
Review: https://review.openstack.org/426493
Reason: This review is > 4 months without comment, and failed Jenkins the last time it was checked. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/426493
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=9810711e75723fc6d66772e10dc0a6ffc8e74198
Submitter: Zuul
Branch: master

commit 9810711e75723fc6d66772e10dc0a6ffc8e74198
Author: Mateusz Kowalski <email address hidden>
Date: Thu Mar 16 10:55:13 2017 +0100

    Make API calls in Volumes view parallel

    In order to increase rendering speed, make
    api.cinder.volume_list_paged, api.nova.server_list
    and api.cinder.volume_snapshot_list parallel.
    For admin panel also api.keystone.tenant_list is
    parallelized.

    Closes-bug: #1660025
    Partial-implements: blueprint fetch-resources-in-parallel

    Change-Id: Ic789ff98a59ba792d77103e7778883562e7977d2

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/horizon 15.0.0.0b2 development milestone.