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Giving state machine implementers a way to opt out from being forced to support snapshotting at arbitrary offset. #22961

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merged 1 commit into from
Oct 8, 2024
Merged

Giving state machine implementers a way to opt out from being forced to support snapshotting at arbitrary offset. #22961

merged 1 commit into from
Oct 8, 2024

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mmaslankaprv
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@mmaslankaprv mmaslankaprv commented Aug 20, 2024 •
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To support fast partition movement in Redpanda the
raft::state_machine_base interface requires state machine implementer
to provide support for taking snapshot at arbitrary, already applied
offset. This requirement is easy to achieve for all existing state
machines as they do not require raft snapshots at all.

In future we may leverage the Raft protocol snapshot as they provide a
nice way to maintain the bounded log size without compromising
consistency.

This PR introduces changes to state_machine_manager and
state_machine_base interfaces allowing state machine implementer to
opt out from the requirement to provide snapshot at offset capability.
Without this feature the partition that the STM is build at will not be
fast movable but the take_snapshot implementation will be very simple
as it will require simply serializing the current in memory state of the
state machine.

Backports Required

  • none - not a bug fix
  • none - this is a backport
  • none - issue does not exist in previous branches
  • none - papercut/not impactful enough to backport
  • v24.2.x
  • v24.1.x
  • v23.3.x

Release Notes

  • none

@mmaslankaprv mmaslankaprv marked this pull request as draft August 20, 2024 13:20
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/dt

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/dt

@vbotbuildovich
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vbotbuildovich commented Aug 27, 2024 •
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ducktape was retried in https://buildkite.com/redpanda/redpanda/builds/53602#019193b1-20d6-4740-9737-9fd1aca2dbd2

ducktape was retried in https://buildkite.com/redpanda/redpanda/builds/53695#019199cb-0acd-444d-8bbb-23f3bd6ba32a

ducktape was retried in https://buildkite.com/redpanda/redpanda/builds/53695#019199cd-d871-49bf-ae6a-ce3860d0f08e

ducktape was retried in https://buildkite.com/redpanda/redpanda/builds/53822#0191a41a-6659-4881-b076-f35ed6756a12

ducktape was retried in https://buildkite.com/redpanda/redpanda/builds/55625#01924c29-032f-4ba2-ade0-25a163f93c5c

ducktape was retried in https://buildkite.com/redpanda/redpanda/builds/55625#01924c29-0331-4189-8a21-8ef6ec430b34

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vbotbuildovich commented Aug 27, 2024 •
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new failures in https://buildkite.com/redpanda/redpanda/builds/53602#019193b3-0ea3-41ce-8ec9-9a413ad3ab3f:

"rptest.tests.availability_test.AvailabilityTests.test_availability_when_one_node_failed"

new failures in https://buildkite.com/redpanda/redpanda/builds/55625#01924c29-032d-4627-8e5c-a7d90a1ac7b3:

"rptest.tests.timely_shutdown_test.ShutdownTest.test_timely_shutdown_with_failures"

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/dt

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/dt

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/dt

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/dt

@mmaslankaprv mmaslankaprv marked this pull request as ready for review September 27, 2024 14:10
bharathv
bharathv reviewed Sep 30, 2024
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a few minor comments.

src/v/raft/state_machine_manager.cc Outdated Show resolved Hide resolved
src/v/raft/state_machine_manager.cc Outdated Show resolved Hide resolved
src/v/raft/state_machine_manager.cc Show resolved Hide resolved
@mmaslankaprv mmaslankaprv force-pushed the stm-snapshot-opt-out branch 4 times, most recently from ace577b to 122e87f Compare October 2, 2024 06:25
@mmaslankaprv mmaslankaprv requested a review from bharathv October 2, 2024 13:51
bharathv
bharathv reviewed Oct 4, 2024
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lgtm

A note on commit history: looks like every commit has the same commit message and I think the last two commits should be squashed, otherwise compilation is broken in the middle commit?

src/v/raft/state_machine_base.h
Comment on lines +136 to +143
if (offset != last_applied_offset()) {
throw std::logic_error(fmt::format(
"State machine that do not support taking snapshot at arbitrary "
"offset can to take snapshot at requested offset: {}, current "
"last applied offset: {}",
offset,
last_applied_offset()));
}
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_apply_units are held by this point, right? Reason I'm asking is because of scheduling points if the units are not held last_applied() may change from L136 and L144. But AFAICT thats not a concern given the units.

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yes, exactly the units are held in the state_machine_manager

@mmaslankaprv
r/stm: added support for state machines without snapshot at offset cap
0f26b8f 
To support fast partition movement in Redpanda the
`raft::state_machine_base` interface requires state machine implementer
to provide support for taking snapshot at arbitrary, already applied
offset. This requirement is easy to achieve for all existing state
machines as they do not require raft snapshots at all.

In future we may leverage the Raft protocol snapshot as they provide a
nice way to maintain the bounded log size without compromising
consistency.

This PR introduces changes to `state_machine_manager` and
`state_machine_base` interfaces allowing state machine implementer to
opt out from the requirement to provide snapshot at offset capability.
Without this feature the partition that the STM is build at will not be
fast movable but the `take_snapshot` implementation will be very simple
as it will require simply serializing the current in memory state of the
state machine.

Signed-off-by: Michał Maślanka <[email protected]>
@mmaslankaprv mmaslankaprv requested a review from bharathv October 4, 2024 07:52
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/ci-repeat 1

@mmaslankaprv mmaslankaprv merged commit dc252d7 into redpanda-data:dev Oct 8, 2024
17 checks passed
@mmaslankaprv mmaslankaprv deleted the stm-snapshot-opt-out branch October 8, 2024 13:44
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@bharathv bharathv bharathv approved these changes

@bashtanov bashtanov Awaiting requested review from bashtanov

@ztlpn ztlpn Awaiting requested review from ztlpn

@Lazin Lazin Awaiting requested review from Lazin

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