f0b8204072
As discussed at our nova meetings, reorganize the juno specs into three directories: - proposed: things proposed which weren't approved - approved: things we approved but didn't implement - implemented: things approved and implemented The first I suspect is the most controversial. I've done this because I worry about the case where a future developer wants to pick up something dropped by a previous developer, but has trouble finding previous proposed specifications on the topic. Note that the actual proposed specs for Juno are adding in a later commit. Change-Id: Idcf55ca37a83d7098dcb7c2971240c4e8fd23dc8
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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===================================================
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Support Console Log migration during Live-migration
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===================================================
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https://blueprints.launchpad.net/nova/+spec/support-console-log-migration
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Implement console log migration during live-migration in the libvirt driver
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Problem description
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===================
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Currently, in libvirt driver with a kvm hypervisor, console output is written
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to console.log. Nova responds to a get-console-log request with the contents
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of this file and this information is useful for debugging issues during boot
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process. However, during a live-migration the contents of the file in the
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source node is discarded.
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There are two issues which play a role in this.
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* The new kvm process in the destination would have already started using
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an empty console log.
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* While the migration progresses the VM in the source node will continue
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to write to the console log.
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Proposed change
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===============
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We propose the following in this blueprint to solve this issue without
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depending on kvm.
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* Require that VIR_MIGRATE_UNDEFINE_SOURCE is not set. Instead wait for the
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condition that the instance is shutoff at the source.
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* During post-live-migration copy the console log be from source node and save
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in the destination node as console.log.1. If log rotation is implemented,
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all the rotated files need to be rotated once.
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* Change get-console-log function such that console.log and console.log.1 are
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merged in the response (within the MAX_CONSOLE_BYTES limit). It log rotation
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is implemented then the function needs to read as many files as it takes to
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fill up the MAX_CONSOLE_BYTES limit.
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* The source VM would get undefined by the periodic task once the database is
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updated with the new hostname.
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Alternatives
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------------
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* Change qemu to move the file content
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* Stream console output to a shared location
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* If spec/libvirt-serial-console is implemented we can leverage on that
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mechanism and trigger a rotation and move it to destination.
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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None
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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None
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Performance Impact
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------------------
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* There's a brief window between the time the VM is activated in the
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destination and before post-live-migration is completed. Any nova
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console-log requests will return almost empty content during this window.
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Other deployer impact
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---------------------
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* If people are using VIR_MIGRATE_UNDEFINE_SOURCE then they need to remove this
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option to get this feature. If this flag exists we will fallback to not
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having the console log migrated.
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Developer impact
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----------------
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None
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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parthipan
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Work Items
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----------
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* Change live-migration to wait for shutoff state if flag
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VIR_MIGRATE_UNDEFINE_SOURCE is not set.
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* Change get_console_log to handle rotated log files
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* Implement console log migration during post-live-migration
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Dependencies
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============
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None
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Testing
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=======
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Tempest tests should be added to test that the console logs are merged in the
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response and catch other corner-cases.
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Documentation Impact
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====================
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We expect to have the following documentation changes:
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* The migration flag changes to get console logs migrated
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* Expected empty console log during the VM offline period in the final stages
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of the migration
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References
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==========
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* https://bugs.launchpad.net/nova/+bug/1203193
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