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fix concurrency on stream execute engine primitives #14586

Merged
merged 6 commits into from
Nov 23, 2023
Merged

fix concurrency on stream execute engine primitives #14586

merged 6 commits into from
Nov 23, 2023

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harshit-gangal
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@harshit-gangal harshit-gangal commented Nov 22, 2023 •
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Description

This PR adds the required lock on the engine primitive with Streaming support where a local state is maintained and needs to be synchronized between parallel calls from underlying callbacks.

The primitive were either returning the wrong result or were causing VTGate panics.

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  • "Backport to:" labels have been added if this change should be back-ported
  • Tests were added or are not required
  • Did the new or modified tests pass consistently locally and on the CI
  • Documentation was added or is not required

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vitess-bot bot commented Nov 22, 2023

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Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

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@vitess-bot vitess-bot bot added NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsIssue A linked issue is missing for this Pull Request NeedsWebsiteDocsUpdate What it says labels Nov 22, 2023
@harshit-gangal harshit-gangal added Type: Bug Component: Query Serving and removed NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsWebsiteDocsUpdate What it says NeedsIssue A linked issue is missing for this Pull Request labels Nov 22, 2023
@github-actions github-actions bot added this to the v19.0.0 milestone Nov 22, 2023
dbussink
dbussink reviewed Nov 22, 2023
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go/vt/vtgate/engine/projection.go
@@ -88,6 +88,7 @@ func (p *Projection) TryStreamExecute(ctx context.Context, vcursor VCursor, bind
env := evalengine.NewExpressionEnv(ctx, bindVars, vcursor)
var once sync.Once
var fields []*querypb.Field
var mu sync.Mutex
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@harshit-gangal Is this one necessary? There's already locking in the implementation here which should afaik handle any concurrency issues.

@vmg Afaik the evalengine.NewExpressionEnv should be concurrent usage safe, or is it not?

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No, it definitely isn't, it contains the VM that is used to execute the expressions. You cannot evaluate two expressions at once in the same VM.

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Ah ok, so we gotta lock here then as well for now unless we'd want to move creating the env inside the callback then.

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The next plan is to create env per shard.

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That refactor would not be part of the backport and will be made as a separate PR.

go/vt/vtgate/engine/limit.go Outdated
@@ -108,6 +110,8 @@ func (l *Limit) TryStreamExecute(ctx context.Context, vcursor VCursor, bindVars
return nil
}

mu.Lock()
defer mu.Unlock()
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Looks like need this for the count, but wonder, should we do this with an atomic counter instead? The usage might be complicated though, so the lock might be a lot easier for now and then to optimize later.

go/vt/vtgate/engine/filter.go Show resolved Hide resolved
@harshit-gangal
fix: projection to check for results field before evaluating, added p…
40878b9 
…rojectio and distinct streaming async test

Signed-off-by: Harshit Gangal <[email protected]>
@harshit-gangal harshit-gangal marked this pull request as ready for review November 23, 2023 07:43
dbussink
dbussink reviewed Nov 23, 2023
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go/vt/vtgate/engine/projection.go Outdated
return vcursor.StreamExecutePrimitive(ctx, p.Input, bindVars, wantfields, func(qr *sqltypes.Result) error {
var err error
if wantfields {
if wantfields && qr.Fields != nil {
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@harshit-gangal This change breaks a bunch of tests it looks like. Why was this changed?

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It looks like this change was made due to the testing in projection_test.go, but I suspect it's a problem with that test? Since it runs concurrent stream results, but even if that happens, it's guaranteed that there would always be a field result first, so I don't think the test models a real scenario then.

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I also think that now that we lock here to also protect the evalengine expression env, we don't need the more elaborate locking around wantfields anymore.

@dbussink
Fix the test primitive and locking
745b0f7 
This ensures that we project fields properly and removes racy behavior
from the limit logic as well by moving up the lock.

Signed-off-by: Dirkjan Bussink <[email protected]>
@dbussink
Move the lock up
9e338a3 
Signed-off-by: Dirkjan Bussink <[email protected]>
@dbussink dbussink merged commit b68b1ed into vitessio:main Nov 23, 2023
115 checks passed
@dbussink dbussink deleted the sync-criticalsection-streamexec branch November 23, 2023 11:14
@vitess-bot vitess-bot bot mentioned this pull request Nov 23, 2023
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@vitess-bot vitess-bot bot mentioned this pull request Nov 23, 2023
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vitess-bot pushed a commit that referenced this pull request Nov 23, 2023
@vitess-bot @dbussink
fix concurrency on stream execute engine primitives (#14586)
e2072b2 
Signed-off-by: Harshit Gangal <[email protected]>
Signed-off-by: Dirkjan Bussink <[email protected]>
Co-authored-by: Dirkjan Bussink <[email protected]>
@vitess-bot vitess-bot bot mentioned this pull request Nov 23, 2023
Merged
vitess-bot pushed a commit that referenced this pull request Nov 23, 2023
@vitess-bot @dbussink
fix concurrency on stream execute engine primitives (#14586)
8214b4e 
Signed-off-by: Harshit Gangal <[email protected]>
Signed-off-by: Dirkjan Bussink <[email protected]>
Co-authored-by: Dirkjan Bussink <[email protected]>
harshit-gangal added a commit that referenced this pull request Nov 23, 2023
@harshit-gangal @dbussink
fix concurrency on stream execute engine primitives (#14586)
e86b889 
Signed-off-by: Harshit Gangal <[email protected]>
Signed-off-by: Dirkjan Bussink <[email protected]>
Co-authored-by: Dirkjan Bussink <[email protected]>
harshit-gangal added a commit that referenced this pull request Nov 23, 2023
@vitess-bot @dbussink @harshit-gangal
[release-17.0] fix concurrency on stream execute engine primitives (#…
0e7d848 
…14586) (#14591)

Signed-off-by: Harshit Gangal <[email protected]>
Signed-off-by: Dirkjan Bussink <[email protected]>
Co-authored-by: vitess-bot[bot] <108069721+vitess-bot[bot]@users.noreply.github.com>
Co-authored-by: Dirkjan Bussink <[email protected]>
Co-authored-by: Harshit Gangal <[email protected]>
harshit-gangal added a commit that referenced this pull request Nov 23, 2023
@vitess-bot @dbussink @harshit-gangal
[release-18.0] fix concurrency on stream execute engine primitives (#…
a3d2515 
…14586) (#14592)

Signed-off-by: Harshit Gangal <[email protected]>
Signed-off-by: Dirkjan Bussink <[email protected]>
Co-authored-by: vitess-bot[bot] <108069721+vitess-bot[bot]@users.noreply.github.com>
Co-authored-by: Dirkjan Bussink <[email protected]>
Co-authored-by: Harshit Gangal <[email protected]>
dbussink added a commit that referenced this pull request Nov 23, 2023
@vitess-bot @harshit-gangal @dbussink
[release-16.0] fix concurrency on stream execute engine primitives (#…
551dbd1 
…14586) (#14590)

Signed-off-by: Harshit Gangal <[email protected]>
Signed-off-by: Dirkjan Bussink <[email protected]>
Co-authored-by: Harshit Gangal <[email protected]>
Co-authored-by: Dirkjan Bussink <[email protected]>
ejortegau pushed a commit to slackhq/vitess that referenced this pull request Dec 13, 2023
@harshit-gangal @dbussink @ejortegau
fix concurrency on stream execute engine primitives (vitessio#14586)
d73d9e2 
Signed-off-by: Harshit Gangal <[email protected]>
Signed-off-by: Dirkjan Bussink <[email protected]>
Co-authored-by: Dirkjan Bussink <[email protected]>
@hmaurer hmaurer mentioned this pull request Mar 21, 2024
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@frouioui frouioui frouioui approved these changes

@vmg vmg vmg approved these changes

@dbussink dbussink dbussink approved these changes

@systay systay Awaiting requested review from systay systay is a code owner

@GuptaManan100 GuptaManan100 Awaiting requested review from GuptaManan100 GuptaManan100 is a code owner

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