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utubettl: fix slow take on busy utubes
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If some of the utubettl for tasks at the top of the queue were busy
most of the time, `take` would slow down for every other task.
This problem is fixed by creating a new space `space_ready`. It
contains first task with `READY` status from each utube.

This solution shows great results for the stated problem, with the cost
of slowing the `put` method (it is ~3 times slower). Thus, this workaround is
disabled by default. To enable it, user should set the
`storage_mode = queue.driver.utubettl.STORAGE_MODE_UTUBE_READY_SPACE` as an option
while creating the tube. As example:
```lua
local test_queue = queue.create_tube('test_queue', 'utubettl',
        {temporary = true, storage_mode = queue.driver.utubettl.STORAGE_MODE_UTUBE_READY_SPACE})
```

Closes #228
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DerekBum committed May 15, 2024
1 parent 293aae0 commit 1e1645c
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10 changes: 5 additions & 5 deletions CHANGELOG.md
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Expand Up @@ -8,16 +8,16 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
## [Unreleased]

### Added
- `storage_mode` option for creating a `utube` tube (#228). It enables the
workaround for slow takes while working with busy tubes.
- `storage_mode` option for creating a `utube` and `utubettl` tube (#228).
It enables the workaround for slow takes while working with busy tubes.

### Fixed

- Stuck in `INIT` state if an instance failed to enter the `running` mode
in time (#226). This fix works only for Tarantool versions >= 2.10.0.
- Slow takes on busy `utube` tubes (#228). The workaround could be enabled by
passing the `storage_mode = "utube_ready_space"` option while creating
the tube.
- Slow takes on busy `utube` and `utubettl` tubes (#228). The workaround could
be enabled by passing the `storage_mode = "utube_ready_space"` option while
creating the tube.

## [1.3.3] - 2023-09-13

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36 changes: 36 additions & 0 deletions README.md
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Expand Up @@ -244,13 +244,49 @@ in strict FIFO order.

This queue type is effectively a combination of `fifottl` and `utube`.

It is advised not to use `utubettl` methods inside transactions with
`read-confirmed` isolation level. It can lead to errors when trying to make
parallel tube methods calls with mvcc enabled.

The following options can be specified when creating a `utubettl` queue:
* `temporary` - boolean - if true, the contents of the queue do not persist
on disk
* `if_not_exists` - boolean - if true, no error will be returned if the tube
already exists
* `on_task_change` - function name - a callback to be executed on every
operation
* `storage_mode` - string - one of
* `queue.driver.utubettl.STORAGE_MODE_DEFAULT` ("default") - default
implementation of `utubettl`
* `queue.driver.utubettl.STORAGE_MODE_UTUBE_READY_SPACE`
("utube_ready_space") - allows processing `take` requests faster, but
by the cost of `put` operations speed. Right now this option is enabled
only for `memtx` engine.
WARNING: this is an experimental storage mode.

Here is a benchmark comparison of these two modes:
* Benchmark for simple `put` and `take` methods. 30k utubes are created
with a single task each. Task creation time is calculated. After that
30k consumers are calling `take` + `ack`, each in the separate fiber.
Time to ack all tasks is calculated. The results are as follows:

| | put (30k) | take+ack |
|---------|-----------|----------|
| default | 200ms | 1.7s |
| ready | 320ms | 1.8s |
* Benchmark for the busy utubes. 10 tubes are created.
Each contains 1000 tasks. After that, 10 consumers are created (each works
on his tube only, one tube — one consumer). Each consumer will
`take`, then `yield` and then `ack` every task from their utube
(1000 tasks each).
After that, we can also run this benchmark with 10k tasks on each utube,
100k tasks and 140k tasks. But all that with 10 utubes and 10 consumers.
The results are as follows:

| | 1k | 10k | 50k | 140k |
|---------|-------|------|------|-------|
| default | 80s | 1.6h | 100h | 1000h |
| ready | 520ms | 5.4s | 28s | 83s |

The following options can be specified when putting a task in a
`utubettl` queue:
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