Balazs Gibizer
9e678b83eb
Move the execution of build_and_run_instance and snapshot_instance to one common long task executor. Originally snapshot ran on the RPC pool, build_and_run_instance ran on the default pool. Also each of these tasks had a separate concurrency limit enforced by a semaphore. After this patch each of these tasks use a common Executor. The size of that executor and the way how we limit the concurrency differs in eventlet and in native threading mode. In eventlet mode we have one big Executor with "unlimit" size and individual semaphores are used for each task type to enforce the configured limits. In threading mode we requests the admin to configure the 2 limits to the same number, and we warn if not. We use that limit (or the max of the 2 limits) as the size of the long task Executor. As the limits are the same we don't enforce individual limit any more. The executor size will ensure the shared limit is kept. As the limit is shared a single operation type can consume the whole limit. Note that while live migration is a long-running task we cannot put it into the same long_task_executor as build and snapshot as we need: 1. a very small limit of concurrent live migrations compared to builds and snapshots 2. a way to cancel live migrations easily that are waiting due to the limit Change-Id: I88a6a593af8a5b518715e1245a76ee54752afe83 Signed-off-by: Balazs Gibizer <gibi@redhat.com>
63 lines
3.2 KiB
YAML
63 lines
3.2 KiB
YAML
---
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upgrade:
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The meaning of the 0 value of the config option
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``[DEFAULT]max_concurrent_live_migrations`` has been changed. In the past
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the implementation of the meaning of "unlimited" used maximum 1000
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concurrent worker greenthreads. For eventlet mode this behavior is kept but
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for the native threading mode it is now reduced to 5 native threads. It is
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almost always a bad idea to change this config option from its default value, 1.
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Please read the `concurrency
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<https://docs.openstack.org/nova/latest/admin/concurrency.html>`__
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guide for more details.
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The default value of the configuration option
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``[DEFAULT]sync_power_state_thread_pool_size`` is changed from 1000 to 5 to
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have a value that is safe to use in native threading mode. If you are still
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using the eventlet mode and relying on a higher value then configure that
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higher value explicitly before the upgrade. Please read the
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`concurrency <https://docs.openstack.org/nova/latest/admin/concurrency.html>`__
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guide for more details.
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The meaning of the 0 value of the config option
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``[DEFAULT]max_concurrent_builds`` has been changed. In the past
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it meant "unlimited" but actually it was limited by the oslo.messaging's
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``executor_thread_pool_size`` config option. For eventlet mode "unlimited"
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now means 1000 concurrent builds. For the native threading mode it is
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now reduced to 10 native threads. Please also read the `concurrency
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<https://docs.openstack.org/nova/latest/admin/concurrency.html>`__
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guide for more details.
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The meaning of the 0 value of the config option
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``[DEFAULT]max_concurrent_snapshots`` has been changed. In the past
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it meant "unlimited" but actually it was limited by the oslo.messaging's
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``executor_thread_pool_size`` config option. For eventlet mode "unlimited"
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now means 1000 concurrent snapshots. For the native threading mode it is
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now reduced to 5 native threads. Please also read the `concurrency
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<https://docs.openstack.org/nova/latest/admin/concurrency.html>`__
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guide for more details.
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In native threading mode the limit expressed by
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``[DEFAULT]max_concurrent_builds`` and
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``[DEFAULT]max_concurrent_snapshots`` configuration options are shared
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across the two operation types as they are executed by the same Executor.
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Therefore the two config options need to be set to the same value. If not
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then nova will use the bigger value as the shared limit. The shared limit
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also means that one operation type can consume the whole limit.
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deprecations:
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The possible 0 value of the configuration option
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``[DEFAULT]max_concurrent_live_migrations`` is deprecated and will be
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removed in a future release. It is almost always a bad idea to change the
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default value, 1, of this config option. If more performant live migration
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is needed, use the ``live_migration_parallel_connections`` config option
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instead.
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The possible 0 value of the configuration option
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``[DEFAULT]max_concurrent_builds`` is deprecated and will be
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removed in a future release.
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- |
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The possible 0 value of the configuration option
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``[DEFAULT]max_concurrent_snapshots`` is deprecated and will be
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removed in a future release.
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