tarantool / tarantool / 37915311274

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Committed by sergepetrenko

Commit Message

box: throttle non-system read view creation

Now that read view versions are always assigned honestly (the previous
commit dropped the reusing mechanism), the read_view_version counter
consumption rate is only bounded by how often users create read views.
At 1000 opens per second the 32-bit counter would wrap around in 49 days,
which would break the block visibility tracking completely.

Bound the rate by throttling non-system read view creation: a new read view
may be opened only if at least 100 ms have passed since the previous one.
Introduced two helpers to deal with it:

 - read_view_is_throttled() tells whether the limit currently forbids
   opening a read view;
 - read_view_throttle() yields until it doesn't.

box.read_view.open() calls read_view_throttle() right before
read_view_new(), so it waits out the interval. Callers that can't afford
a fiber yield, for example Tarantool EE's C API for raw read views, call
read_view_is_throttled() and fail with the new ER_READ_VIEW_THROTTLED
error instead.

System read views (checkpoints, join) are not throttled - they are rare
by nature. Existing tests, which open read views in tight loops, use the
internal tweak to disable throttling.

Closes #13332

@TarantoolBot document
Title: Describe read view creation throttling
Since: 3.9.0, 3.8.2, 3.7.2

https://www.tarantool.io/en/doc/latest/platform/ddl_dml/read_views/#limitations

Read view creation is rate-limited: a new read view can be opened no more
often than once every 100 milliseconds. If
:ref:`box.read_view.open() <box-read_view-open>` is called before this
interval has elapsed since the previous read view was opened, it blocks
the calling fiber until the interval has elapsed. System read views
created, for example, to make a
:ref:`checkpoint <book_cfg_checkpoint_daemon>` or join a new
:ref:`replica <replication-architecture>` are not affected.

--

https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_read_view/open/

Read view creation ... (continued)

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